PRO-BOOST-N: Prostate-First Versus Combined Prostate and Nodal Dose Escalation in PSMA PET-Staged Node-Positive Prostate Cancer (PRO-BOOST-N)

PRO-BOOST-N: A Randomized Phase II/III Trial Evaluating Prostate-First Versus Combined Prostate and Nodal Dose Escalation in PSMA PET-Staged Node-Positive Prostate Cancer Using an Ultrahypofractionated Whole-Pelvis Radiotherapy Platform

Patients with prostate cancer and pelvic lymph node involvement (cN1M0) identified on PSMA PET imaging represent a biologically aggressive yet potentially curable disease population. Contemporary management relies on multimodality treatment combining definitive radiotherapy to the prostate and pelvic lymph nodes with long-term androgen deprivation therapy (ADT), often intensified with androgen receptor pathway inhibitors. Despite these advances, a substantial proportion of patients still develop distant metastatic disease, highlighting the need to optimize local-regional treatment strategies in the era of molecular imaging.

The introduction of PSMA PET has fundamentally altered staging accuracy in prostate cancer, enabling earlier and more precise detection of pelvic nodal disease. However, most existing evidence guiding radiotherapy dose prescription in node-positive prostate cancer originates from the pre-PSMA era. As a result, it remains unclear how best to integrate prostate-directed and nodal-directed dose escalation strategies when disease extent is defined by modern molecular imaging. In particular, it is unknown whether long-term disease control is primarily driven by durable intraprostatic tumor eradication, by aggressive treatment of involved lymph nodes, or by a combination of both.

PRO-BOOST-N is a prospective, multicenter, randomized phase II/III clinical trial designed to address this critical evidence gap. The trial evaluates prostate-first versus combined prostate and nodal dose escalation strategies in patients with PSMA PET-staged node-positive (cN1M0) prostate cancer treated within a standardized ultrahypofractionated whole-pelvis radiotherapy framework. All enrolled patients indicated for definitive treatment undergo mandatory baseline PSMA PET/CT to confirm pelvic lymph node involvement and exclude distant metastatic disease.

All patients receive a uniform radiotherapy backbone consisting of ultrahypofractionated whole-pelvis radiotherapy delivered in five fractions, combined with long-term ADT. Use of androgen receptor pathway inhibitors is permitted and encouraged according to contemporary clinical practice and local availability, ensuring the relevance of the trial to real-world treatment settings.

Using a 2×2 factorial randomized design, PRO-BOOST-N evaluates two independent treatment factors. The primary randomized comparison assesses whether ablative prostate dose escalation improves oncologic outcomes compared with contemporary SBRT-based definitive prostate radiotherapy without additional boost. Prostate dose escalation may be delivered using one of three protocol-defined modalities-high-dose-rate brachytherapy, low-dose-rate brachytherapy, or single-fraction SBRT-according to institutional expertise. This comparison directly tests the hypothesis that durable intraprostatic disease control is the dominant determinant of long-term systemic disease suppression in node-positive prostate cancer.

The key secondary, hierarchically tested comparison evaluates the role of nodal dose escalation by comparing two predefined dose levels delivered to PSMA PET-positive pelvic lymph nodes. These dose levels reflect intermediate versus higher nodal boost strategies based on biologically effective dose concepts specific to prostate cancer radiobiology. To ensure patient safety and protocol feasibility, organ-at-risk-driven nodal dose de-escalation is permitted within the higher-dose arm, without altering randomization assignment.

The primary endpoint of the trial is metastasis-free survival. Secondary endpoints include overall survival, radiographic progression-free survival assessed primarily using PSMA PET imaging, intraprostatic and regional nodal control, time to castration-resistant prostate cancer, time to next systemic therapy, treatment-related toxicity graded according to CTCAE version 5.0, and patient-reported outcomes assessing urinary, bowel, sexual, and global quality of life.

By prospectively and hierarchically evaluating prostate and nodal dose escalation strategies within a modern PSMA PET-guided and ultrahypofractionated radiotherapy platform, PRO-BOOST-N aims to define the optimal radiotherapy intensification approach for patients with node-positive prostate cancer. The results of this study are expected to directly inform clinical practice, guideline development, and future treatment individualization in the PSMA PET era.

Study Overview

• Status: Recruiting
• Conditions: Prostate Cancer; Brachytherapy; Dose Escalation: Solid Tumors; Stereotactic Body Radiation Therapy (SBRT); Regionally Advanced Prostate Cancer
• Intervention / Treatment: Radiation: Ultrahypofractionated Whole-Pelvis Radiotherapy; Radiation: SBRT-Based Prostate Radiotherapy (No Boost); Radiation: Intermediate Nodal Dose Escalation; Drug: Androgen Deprivation Therapy (ADT); Drug: Androgen Receptor Pathway Inhibitors (ARPIs); Radiation: Higher Nodal Dose Escalation; Radiation: Ablative Prostate Boost

Detailed Description

Disease Background and Unmet Clinical Need Prostate cancer with pelvic lymph node involvement (cN1M0) represents a clinically challenging disease state characterized by a substantial risk of subsequent metastatic progression and prostate cancer-specific mortality. Historically, patients with node-positive disease were frequently considered to harbor occult systemic spread and were often managed with androgen deprivation therapy (ADT) alone. This treatment paradigm was largely driven by limitations in imaging sensitivity and by the perception that regional nodal involvement inevitably reflected disseminated disease.

Over the past two decades, accumulating clinical evidence has fundamentally altered this view. Multiple retrospective analyses, population-based studies, and prospective randomized trials have demonstrated that definitive local-regional radiotherapy combined with long-term ADT can achieve durable disease control and improve survival outcomes in selected patients with node-positive prostate cancer. These findings have established combined radiotherapy and systemic therapy as the contemporary standard of care for cN1 disease treated with curative intent.

Despite these advances, outcomes remain heterogeneous. Even with modern multimodality treatment, a substantial proportion of patients experience disease progression, most commonly manifesting as distant metastatic spread. This persistent failure pattern highlights an unmet clinical need to optimize local-regional treatment strategies and to better define the relative contributions of prostate-directed and nodal-directed radiotherapy dose escalation to long-term disease control.

Transformation of Staging in the PSMA PET Era The widespread clinical adoption of prostate-specific membrane antigen positron emission tomography (PSMA PET) has profoundly transformed staging and risk stratification in prostate cancer. PSMA PET offers markedly superior sensitivity and specificity compared with conventional imaging for the detection of both nodal and distant metastatic disease. This improvement has led to significant stage migration, particularly among patients previously classified as node-negative on conventional imaging who are now identified as having limited pelvic nodal involvement.

As a result, the contemporary population of patients classified as cN1M0 based on PSMA PET represents a biologically distinct cohort compared with historical node-positive populations. Many of these patients harbor small-volume nodal disease that would previously have remained undetected and untreated. Consequently, existing evidence guiding radiotherapy dose prescription and target volume selection-largely derived from the pre-PSMA era-may no longer be directly applicable to current clinical practice.

Importantly, while PSMA PET improves detection of nodal disease, it does not in itself define the optimal therapeutic response. The identification of nodal metastases raises critical questions regarding treatment intensification: whether improved outcomes are best achieved through more aggressive treatment of the primary prostate tumor, through escalation of dose to involved lymph nodes, or through a combined strategy addressing both compartments.

Biological Rationale for Local-Regional Disease Control From a biological perspective, prostate cancer progression is increasingly understood as a dynamic, multistep process in which the primary tumor and regional nodal metastases may serve as ongoing sources of metastatic dissemination. Molecular and phylogenetic studies suggest that, in many patients, nodal metastases arise directly from dominant intraprostatic tumor clones and may retain limited metastatic competence. In this context, effective eradication of both intraprostatic disease and regional nodal deposits may interrupt further metastatic seeding and delay or prevent the emergence of castration-resistant disease.

Durable intraprostatic disease control has consistently been associated with improved long-term outcomes across multiple prostate cancer risk groups. Dose escalation to the prostate has been shown to improve biochemical control, local control, and, in selected analyses, metastasis-free and overall survival. These benefits have been demonstrated using a variety of techniques, including conventionally fractionated radiotherapy, moderate and ultrahypofractionation, stereotactic body radiotherapy (SBRT), and brachytherapy boost approaches.

In node-positive prostate cancer specifically, emerging real-world and propensity score-matched analyses suggest that intensified prostate-directed radiotherapy may exert a dominant influence on systemic disease control. Patients receiving high biologically effective doses to the prostate, particularly through brachytherapy boost techniques, appear to experience improved metastasis-free survival even in the presence of pelvic nodal disease. These observations form the biological foundation of the central hypothesis underlying PRO-BOOST-N.

Prostate Dose Escalation as the Primary Hypothesis The primary hypothesis of PRO-BOOST-N is that durable intraprostatic tumor eradication represents the principal determinant of long-term systemic disease suppression in patients with PSMA PET-staged node-positive prostate cancer. According to this hypothesis, effective sterilization of the primary tumor reduces the reservoir of clonogenic cells capable of seeding distant metastases, thereby improving metastasis-free survival regardless of the presence of limited nodal disease.

This hypothesis is supported by multiple lines of evidence. In high-risk and very high-risk prostate cancer, prostate dose escalation has consistently been associated with improved disease control. In node-positive cohorts, retrospective analyses have demonstrated that higher prostate dose correlates with improved outcomes, while nodal dose escalation has shown less consistent benefit once prostate dose and systemic therapy are optimized.

PRO-BOOST-N is designed to prospectively and rigorously test this hypothesis in a randomized setting by comparing contemporary SBRT-based definitive prostate radiotherapy without additional boost to ablative prostate dose escalation delivered using established high-dose techniques.

Uncertainty and Rationale Regarding Nodal Dose Escalation In contrast to the relatively consistent signal supporting prostate dose escalation, the role of aggressive dose escalation to involved pelvic lymph nodes remains uncertain. While the biological rationale for nodal ablation is compelling, clinical evidence remains heterogeneous. Retrospective series have demonstrated the technical feasibility and safety of delivering escalated doses to involved pelvic lymph nodes using modern intensity-modulated techniques, including simultaneous integrated boost approaches.

However, the incremental clinical benefit of escalating nodal dose beyond moderate biologically effective levels has not been consistently demonstrated. Some analyses suggest a dose-response relationship up to approximately 55-60 Gy EQD2, with a potential plateau thereafter. Other studies fail to demonstrate an independent association between nodal dose and survival outcomes when prostate dose and systemic therapy are taken into account. Furthermore, aggressive nodal dose escalation may increase the risk of gastrointestinal and genitourinary toxicity, particularly in hypofractionated or ultrahypofractionated regimens.

Given these uncertainties, PRO-BOOST-N incorporates nodal dose escalation as a key secondary objective, evaluated hierarchically after the primary prostate dose escalation comparison. This design reflects both biological plausibility and the current state of clinical evidence, while minimizing the risk of overinterpreting potentially marginal effects.

Rationale for Ultrahypofractionated Whole-Pelvis Radiotherapy Prostate cancer exhibits a low α/β ratio, making it particularly suitable for hypofractionated and ultrahypofractionated radiotherapy schedules. Advances in treatment planning, image guidance, and motion management have enabled safe delivery of large fraction sizes with acceptable toxicity profiles. Emerging clinical data suggest that whole-pelvis radiotherapy can be delivered in a limited number of fractions when modern techniques are applied, even in high-risk and node-positive settings.

An ultrahypofractionated whole-pelvis radiotherapy platform offers several advantages. It provides a standardized treatment backbone that minimizes variability in fractionation and overall treatment time, enhances patient convenience, and facilitates protocol adherence across multiple centers. Importantly, it enables direct comparison of prostate and nodal dose escalation strategies within a unified fractionation framework, reducing confounding and improving interpretability of results.

Study Design and Overall Structure PRO-BOOST-N is a prospective, multicenter, randomized phase II/III clinical trial designed to evaluate the relative and combined impact of prostate-directed and nodal-directed radiotherapy dose escalation in patients with PSMA PET-staged node-positive (cN1M0) prostate cancer. All eligible patients undergo mandatory baseline PSMA PET/CT to confirm pelvic lymph node involvement and exclude distant metastatic disease. Multiparametric magnetic resonance imaging of the prostate is strongly recommended to support local staging and target delineation.

All enrolled patients receive a standardized ultrahypofractionated external beam radiotherapy backbone consisting of whole-pelvis radiotherapy delivered in five fractions. This backbone includes elective pelvic nodal volumes and the prostate and is delivered using modern intensity-modulated techniques with daily image guidance. All patients receive long-term ADT as the systemic therapy backbone, with optional use of androgen receptor pathway inhibitors according to contemporary clinical practice and local availability.

Randomization Framework and Treatment Factors The trial employs a 2×2 factorial randomized design incorporating two independent treatment factors. The first factor evaluates prostate dose escalation strategy and constitutes the primary randomized comparison. Patients are assigned to receive either contemporary SBRT-based definitive prostate radiotherapy without additional boost or ablative prostate dose escalation delivered using one of three protocol-defined modalities: high-dose-rate brachytherapy, low-dose-rate brachytherapy, or single-fraction SBRT boost. The choice of boost modality is based on institutional expertise and availability, with optional sub-randomization where multiple modalities are available.

The second factor evaluates nodal dose escalation strategy and constitutes a key secondary, hierarchically tested comparison. Patients are randomized to receive one of two predefined dose levels to PSMA PET-positive pelvic lymph nodes, corresponding to intermediate versus higher biologically effective doses. Nodal boost doses are delivered using a simultaneous integrated boost approach within the ultrahypofractionated whole-pelvis radiotherapy plan. Protocol-defined organ-at-risk-driven nodal dose de-escalation is permitted within the higher-dose arm to ensure patient safety and feasibility.

Systemic Therapy Integration and Real-World Relevance All patients enrolled in PRO-BOOST-N receive long-term androgen deprivation therapy in accordance with contemporary standards of care. The use of androgen receptor pathway inhibitors is permitted and encouraged based on clinical indications, local availability, and patient comorbidities. Systemic therapy is not randomized, reflecting real-world practice, but planned use of ARPIs is recorded at baseline and incorporated into stratification and exploratory analyses.

This approach ensures that the trial evaluates radiotherapy dose escalation strategies within the context of modern systemic treatment, enhancing the external validity and clinical relevance of the results.

Endpoints and Outcome Assessment The primary endpoint of PRO-BOOST-N is metastasis-free survival, defined as the time from randomization to the occurrence of distant metastatic disease or death from any cause. Pelvic nodal progression alone does not constitute a metastasis-free survival event and is analyzed separately under regional control endpoints.

Secondary endpoints include overall survival, radiographic progression-free survival assessed primarily using PSMA PET imaging, intraprostatic local control, regional nodal control, time to castration-resistant prostate cancer, time to next systemic therapy, acute and late treatment-related toxicity graded according to CTCAE version 5.0, and patient-reported outcomes assessing urinary, bowel, sexual, and global quality of life.

Imaging, Follow-up, and Failure Pattern Characterization PSMA PET imaging is central to both baseline staging and assessment of disease progression. Imaging is performed at baseline and at the time of suspected progression based on PSA kinetics or clinical findings. This strategy enables precise localization and characterization of disease recurrence and allows differentiation between local recurrence, regional nodal progression, oligometastatic dissemination, and polymetastatic disease.

Patients are followed longitudinally with standardized clinical assessments, PSA and testosterone monitoring, toxicity reporting, and patient-reported outcome measures. Long-term follow-up is planned to capture late disease events, late toxicity, and survival outcomes.

Statistical Philosophy and Phase II/III Transition PRO-BOOST-N is designed as a seamless phase II/III trial. The initial phase II component focuses on feasibility, treatment compliance, and early safety. Upon meeting predefined criteria, the trial transitions seamlessly into the phase III component without interruption of accrual. Hierarchical testing preserves statistical power for the primary hypothesis while allowing formal evaluation of secondary hypotheses.

Expected Clinical and Scientific Impact By prospectively and hierarchically evaluating prostate-first versus combined prostate and nodal dose escalation strategies within a PSMA PET-guided and ultrahypofractionated radiotherapy framework, PRO-BOOST-N seeks to address one of the most important unresolved questions in contemporary prostate cancer management. The results of this trial have the potential to directly inform clinical practice, refine guideline recommendations, and optimize treatment individualization for patients with node-positive prostate cancer in the PSMA PET era.

• Study Type: Interventional
• Enrollment (Estimated): 1600
• Phase: Phase 2; Phase 3

Contacts and Locations

• Study Contact: Name: Mateusz Bilski, MD, PhD; Phone Number: 048 84 535 99 10; Email: bilskimat@gmail.com
• Study Contact Backup: Name: Mateusz Bilski, MD,PhD; Phone Number: 048 84 535 99 10; Email: bilskimat@gmail.com

Study Locations

• Poland
  • Lublin Voivodeship
    • Zamość, Lublin Voivodeship, Poland, 22-400
      • Recruiting
      • Affidea Nu-Med, Center of Oncological Diagnostics and Therapy
      • Contact: Mateusz Edward Bilski, MD, PhD; Phone Number: 048 84 535 99 10; Email: bilskimat@gmail.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Histologically confirmed adenocarcinoma of the prostate.
• Prostate cancer with clinically positive pelvic lymph nodes (cN1) without evidence of distant metastatic disease.
• Pelvic lymph node involvement limited to regional pelvic lymph nodes (obturator, internal iliac, external iliac, presacral), as assessed by conventional imaging and/or PSMA PET/CT.
• No evidence of distant metastatic disease (M0), including absence of non-regional nodal, bone, or visceral metastases.
• Candidate for definitive radiotherapy to the prostate and elective pelvic lymph nodes.
• Planned treatment with androgen deprivation therapy with or without androgen receptor pathway inhibitors according to protocol.
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2.
• Adequate organ function allowing delivery of protocol-defined radiotherapy and systemic therapy.
• Age ≥18 years.
• Ability to understand and willingness to sign a written informed consent.

Exclusion Criteria:

• Evidence of distant metastatic disease (M1), including non-regional lymph node, bone, or visceral metastases.
• Prior definitive local therapy for prostate cancer, including radical prostatectomy, whole-gland radiotherapy, or brachytherapy.
• Prior pelvic radiotherapy for any indication that would overlap planned treatment fields.
• Prior systemic therapy for prostate cancer other than protocol-allowed neoadjuvant androgen deprivation therapy.
• History of castration-resistant prostate cancer.
• Concurrent malignancy requiring active treatment, except non-melanoma skin cancer or other malignancies with negligible risk of interference with study outcomes.
• Severe uncontrolled comorbidities that would preclude safe delivery of radiotherapy or systemic therapy.
• Any condition that, in the opinion of the investigator, would interfere with patient safety or compliance with the study protocol.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Factorial Assignment
• Masking: None (Open Label)

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Arm 1: A0B1 - No Prostate Boost + Intermediate Nodal Dose; Participants receive ultrahypofractionated whole-pelvis radiotherapy (25 Gy in 5 fractions) with a simultaneous integrated boost to the prostate delivering 36.25 Gy in 5 fractions, without additional prostate boost. PSMA PET-positive pelvic lymph nodes receive an intermediate nodal dose escalation (27.75 Gy in 5 fractions). All patients receive long-term androgen deprivation therapy with or without androgen receptor pathway inhibitors according to protocol.	Radiation: Ultrahypofractionated Whole-Pelvis Radiotherapy; Whole-pelvis external beam radiotherapy delivered using VMAT or IMRT techniques to elective pelvic lymph node volumes and the prostate. Treatment is prescribed as 25 Gy in 5 fractions and delivered with daily image guidance, serving as the standardized radiotherapy backbone for all study arms.; Other Names: Whole-Pelvis Radiotherapy (WPRT); Radiation: SBRT-Based Prostate Radiotherapy (No Boost); Definitive prostate radiotherapy delivered as a simultaneous integrated boost within the ultrahypofractionated whole-pelvis radiotherapy plan. The prostate receives a total dose of 36.25 Gy in 5 fractions without additional prostate boost beyond this dose.; Other Names: Definitive Prostate SBRT; Prostate SBRT 36.25 Gy; Radiation: Intermediate Nodal Dose Escalation; Dose escalation to PSMA PET-positive pelvic lymph nodes delivered using a simultaneous integrated boost technique within the ultrahypofractionated whole-pelvis radiotherapy plan. The prescribed nodal boost dose is 27.75 Gy in 5 fractions.; Other Names: PSMA PET-Guided Nodal Boost (Intermediate Dose); Pelvic Nodal SIB 27.75 Gy; Drug: Androgen Deprivation Therapy (ADT); Androgen deprivation therapy administered as long-term systemic treatment in all study arms. ADT is delivered using luteinizing hormone-releasing hormone (LHRH) agonists or antagonists according to institutional practice and protocol-defined duration. ADT is initiated before or during radiotherapy and continued after completion of radiotherapy as specified in the study protocol.; Drug: Androgen Receptor Pathway Inhibitors (ARPIs); Androgen receptor pathway inhibitors may be administered in combination with androgen deprivation therapy according to contemporary clinical practice, local availability, and patient-specific considerations. The use of ARPIs is permitted but not randomized and includes approved agents targeting androgen receptor signaling.
Experimental: Arm 2: A0B2 - No Prostate Boost + Higher Nodal Dose; Participants receive ultrahypofractionated whole-pelvis radiotherapy (25 Gy in 5 fractions) with a simultaneous integrated boost to the prostate delivering 36.25 Gy in 5 fractions, without additional prostate boost. PSMA PET-positive pelvic lymph nodes receive a higher nodal dose escalation (30 Gy in 5 fractions), with protocol-defined organ-at-risk-driven dose de-escalation permitted if required. All patients receive long-term androgen deprivation therapy with or without androgen receptor pathway inhibitors according to protocol.	Radiation: Ultrahypofractionated Whole-Pelvis Radiotherapy; Whole-pelvis external beam radiotherapy delivered using VMAT or IMRT techniques to elective pelvic lymph node volumes and the prostate. Treatment is prescribed as 25 Gy in 5 fractions and delivered with daily image guidance, serving as the standardized radiotherapy backbone for all study arms.; Other Names: Whole-Pelvis Radiotherapy (WPRT); Radiation: SBRT-Based Prostate Radiotherapy (No Boost); Definitive prostate radiotherapy delivered as a simultaneous integrated boost within the ultrahypofractionated whole-pelvis radiotherapy plan. The prostate receives a total dose of 36.25 Gy in 5 fractions without additional prostate boost beyond this dose.; Other Names: Definitive Prostate SBRT; Prostate SBRT 36.25 Gy; Drug: Androgen Deprivation Therapy (ADT); Androgen deprivation therapy administered as long-term systemic treatment in all study arms. ADT is delivered using luteinizing hormone-releasing hormone (LHRH) agonists or antagonists according to institutional practice and protocol-defined duration. ADT is initiated before or during radiotherapy and continued after completion of radiotherapy as specified in the study protocol.; Drug: Androgen Receptor Pathway Inhibitors (ARPIs); Androgen receptor pathway inhibitors may be administered in combination with androgen deprivation therapy according to contemporary clinical practice, local availability, and patient-specific considerations. The use of ARPIs is permitted but not randomized and includes approved agents targeting androgen receptor signaling.; Radiation: Higher Nodal Dose Escalation; Dose escalation to PSMA PET-positive pelvic lymph nodes delivered using a simultaneous integrated boost technique within the ultrahypofractionated whole-pelvis radiotherapy plan. The prescribed nodal boost dose is 30 Gy in 5 fractions, with protocol-defined organ-at-risk-driven dose de-escalation permitted if required.; Other Names: PSMA PET-Guided Nodal Boost (High Dose); Pelvic Nodal SIB 30 Gy
Experimental: Arm 3: A1B1 - Prostate Boost + Intermediate Nodal Dose; Participants receive ultrahypofractionated whole-pelvis radiotherapy (25 Gy in 5 fractions) to the prostate and pelvic lymph nodes, followed by ablative prostate dose escalation using one of the following protocol-defined modalities: high-dose-rate brachytherapy, low-dose-rate brachytherapy, or single-fraction stereotactic body radiotherapy boost. PSMA PET-positive pelvic lymph nodes receive an intermediate nodal dose escalation (27.75 Gy in 5 fractions). All patients receive long-term androgen deprivation therapy with or without androgen receptor pathway inhibitors according to protocol.	Radiation: Ultrahypofractionated Whole-Pelvis Radiotherapy; Whole-pelvis external beam radiotherapy delivered using VMAT or IMRT techniques to elective pelvic lymph node volumes and the prostate. Treatment is prescribed as 25 Gy in 5 fractions and delivered with daily image guidance, serving as the standardized radiotherapy backbone for all study arms.; Other Names: Whole-Pelvis Radiotherapy (WPRT); Radiation: Intermediate Nodal Dose Escalation; Dose escalation to PSMA PET-positive pelvic lymph nodes delivered using a simultaneous integrated boost technique within the ultrahypofractionated whole-pelvis radiotherapy plan. The prescribed nodal boost dose is 27.75 Gy in 5 fractions.; Other Names: PSMA PET-Guided Nodal Boost (Intermediate Dose); Pelvic Nodal SIB 27.75 Gy; Drug: Androgen Deprivation Therapy (ADT); Androgen deprivation therapy administered as long-term systemic treatment in all study arms. ADT is delivered using luteinizing hormone-releasing hormone (LHRH) agonists or antagonists according to institutional practice and protocol-defined duration. ADT is initiated before or during radiotherapy and continued after completion of radiotherapy as specified in the study protocol.; Drug: Androgen Receptor Pathway Inhibitors (ARPIs); Androgen receptor pathway inhibitors may be administered in combination with androgen deprivation therapy according to contemporary clinical practice, local availability, and patient-specific considerations. The use of ARPIs is permitted but not randomized and includes approved agents targeting androgen receptor signaling.; Radiation: Ablative Prostate Boost; Ablative prostate dose escalation delivered after completion of ultrahypofractionated whole-pelvis radiotherapy. The prostate boost is delivered using one of the following protocol-defined modalities according to institutional expertise: high-dose-rate brachytherapy (15 Gy in 1 fraction), low-dose-rate brachytherapy (110 Gy permanent implant), or single-fraction stereotactic body radiotherapy boost (15 Gy in 1 fraction).; Other Names: Prostate Boost Radiotherapy; Whole-Gland Prostate Boost
Experimental: Arm 4: A1B2 - Prostate Boost + Higher Nodal Dose; Participants receive ultrahypofractionated whole-pelvis radiotherapy (25 Gy in 5 fractions) to the prostate and pelvic lymph nodes, followed by ablative prostate dose escalation using one of the following protocol-defined modalities: high-dose-rate brachytherapy, low-dose-rate brachytherapy, or single-fraction stereotactic body radiotherapy boost. PSMA PET-positive pelvic lymph nodes receive a higher nodal dose escalation (30 Gy in 5 fractions), with protocol-defined organ-at-risk-driven dose de-escalation permitted if required. All patients receive long-term androgen deprivation therapy with or without androgen receptor pathway inhibitors according to protocol.	Radiation: Ultrahypofractionated Whole-Pelvis Radiotherapy; Whole-pelvis external beam radiotherapy delivered using VMAT or IMRT techniques to elective pelvic lymph node volumes and the prostate. Treatment is prescribed as 25 Gy in 5 fractions and delivered with daily image guidance, serving as the standardized radiotherapy backbone for all study arms.; Other Names: Whole-Pelvis Radiotherapy (WPRT); Drug: Androgen Deprivation Therapy (ADT); Androgen deprivation therapy administered as long-term systemic treatment in all study arms. ADT is delivered using luteinizing hormone-releasing hormone (LHRH) agonists or antagonists according to institutional practice and protocol-defined duration. ADT is initiated before or during radiotherapy and continued after completion of radiotherapy as specified in the study protocol.; Drug: Androgen Receptor Pathway Inhibitors (ARPIs); Androgen receptor pathway inhibitors may be administered in combination with androgen deprivation therapy according to contemporary clinical practice, local availability, and patient-specific considerations. The use of ARPIs is permitted but not randomized and includes approved agents targeting androgen receptor signaling.; Radiation: Higher Nodal Dose Escalation; Dose escalation to PSMA PET-positive pelvic lymph nodes delivered using a simultaneous integrated boost technique within the ultrahypofractionated whole-pelvis radiotherapy plan. The prescribed nodal boost dose is 30 Gy in 5 fractions, with protocol-defined organ-at-risk-driven dose de-escalation permitted if required.; Other Names: PSMA PET-Guided Nodal Boost (High Dose); Pelvic Nodal SIB 30 Gy; Radiation: Ablative Prostate Boost; Ablative prostate dose escalation delivered after completion of ultrahypofractionated whole-pelvis radiotherapy. The prostate boost is delivered using one of the following protocol-defined modalities according to institutional expertise: high-dose-rate brachytherapy (15 Gy in 1 fraction), low-dose-rate brachytherapy (110 Gy permanent implant), or single-fraction stereotactic body radiotherapy boost (15 Gy in 1 fraction).; Other Names: Prostate Boost Radiotherapy; Whole-Gland Prostate Boost

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Metastasis-Free Survival (MFS)	Metastasis-free survival is defined as the time from randomization to the first occurrence of distant metastatic disease or death from any cause, whichever occurs first. Distant metastases include non-regional lymph node, bone, or visceral metastases confirmed by PSMA PET imaging or other clinically indicated imaging modalities. Pelvic nodal progression alone does not constitute a metastasis-free survival event.	Up to 10 years from randomization

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall Survival (OS)	Overall survival is defined as the time from randomization to death from any cause. Patients alive at the time of analysis will be censored at the date of last follow-up.	Up to 10 years from randomization
Radiographic Progression-Free Survival (rPFS)	Radiographic progression-free survival is defined as the time from randomization to radiographic disease progression or death from any cause, whichever occurs first. Radiographic progression is assessed primarily using PSMA PET imaging and includes local, regional nodal, or distant disease progression according to protocol-defined criteria.	Up to 10 years from randomization
Intraprostatic Local Control (iLC)	Intraprostatic local control is defined as the absence of radiographic or histologically confirmed recurrence within the prostate gland after completion of radiotherapy, assessed using PSMA PET imaging, multiparametric MRI, or biopsy when clinically indicated.	Up to 10 years from randomization
Regional Pelvic Nodal Control (rNC)	Regional pelvic nodal control is defined as the absence of progression or recurrence within pelvic lymph nodes treated at baseline. Pelvic nodal progression is assessed using PSMA PET imaging or other clinically indicated imaging modalities.	Up to 10 years from randomization
Time to Castration-Resistant Prostate Cancer (CRPC)	Time to castration-resistant prostate cancer is defined as the time from randomization to the development of castration-resistant disease, according to standard clinical and biochemical criteria, while maintaining castrate levels of testosterone.	Up to 10 years from randomization
Time to Next Systemic Therapy (TTNS)	Time to next systemic therapy is defined as the time from randomization to initiation of the first subsequent systemic anticancer treatment beyond protocol-defined androgen deprivation therapy, including chemotherapy or additional hormonal agents.	Up to 10 years from randomization
Acute Treatment-Related Toxicity	Acute treatment-related toxicity is assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 and includes adverse events occurring during radiotherapy and up to 90 days after completion of radiotherapy.	Up to 90 days after completion of radiotherapy
Late Treatment-Related Toxicity	Late treatment-related toxicity is assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 and includes adverse events occurring more than 90 days after completion of radiotherapy.	Up to 10 years after completion of radiotherapy
Time to Polyprogressive or Polyrecurrent Disease (TTPD)	Time to polyprogressive or polyrecurrent disease is defined as the time from randomization to first documentation of polyprogressive or polyrecurrent disease, defined as the development of more than five new and/or regrowing metastatic lesions (regional and/or non-regional) or widespread metastatic disease precluding further metastasis-directed therapy.	Up to 10 years from randomization
Expanded Prostate Cancer Index Composite-26 (EPIC-26) Urinary Domain Score	Change from baseline in urinary quality of life assessed using the Expanded Prostate Cancer Index Composite-26 (EPIC-26) urinary domain. The EPIC-26 urinary domain is scored on a 0-100 scale, where higher scores indicate better urinary function and fewer urinary symptoms.	Up to 10 years from randomization
EPIC-26 Bowel Domain Score	Change from baseline in bowel quality of life assessed using the Expanded Prostate Cancer Index Composite-26 (EPIC-26) bowel domain. Scores range from 0 to 100, with higher scores indicating better bowel function and fewer bowel-related symptoms.	From baseline to 10 years after randomization
EPIC-26 Sexual Domain Score	Change from baseline in sexual function assessed using the Expanded Prostate Cancer Index Composite-26 (EPIC-26) sexual domain. Scores range from 0 to 100, with higher scores indicating better sexual function.	From baseline to 10 years after randomization
International Prostate Symptom Score (IPSS)	Change from baseline in lower urinary tract symptoms assessed using the International Prostate Symptom Score (IPSS). The IPSS ranges from 0 to 35, where higher scores indicate worse urinary symptoms.	From baseline to 10 years after randomization
International Index of Erectile Function-5 (IIEF-5)	Change from baseline in erectile function assessed using the International Index of Erectile Function-5 (IIEF-5). The IIEF-5 score ranges from 5 to 25, where higher scores indicate better erectile function.	From baseline to 10 years after randomization
EORTC Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) Global Health Status	Change from baseline in global health-related quality of life assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) global health status scale. Scores range from 0 to 100, where higher scores indicate better global health status.	From baseline to 10 years after randomization
EORTC Quality of Life Questionnaire-Prostate Module (EORTC QLQ-PR25)	Change from baseline in prostate cancer-specific quality of life assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Prostate Module (EORTC QLQ-PR25). Scores range from 0 to 100. For functional scales, higher scores indicate better functioning; for symptom scales, higher scores indicate worse symptoms.	From baseline to 10 years after randomization

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Patterns of First Disease Progression	Characterization of the first site and extent of disease progression, categorized as local (prostate), regional pelvic nodal, or distant metastatic progression, and classified as oligoprogressive or oligorecurrent disease (≤5 new or regrowing metastatic lesions) or polyprogressive or polymetastatic disease (>5 lesions).	Up to 10 years from randomization
Hazard Ratio for Metastasis-Free Survival per 10 Gy Increase in Delivered Prostate EQD2	Hazard ratio for metastasis-free survival associated with each 10 Gy increase in delivered prostate equivalent dose in 2 Gy fractions (EQD2, α/β = 1.5), estimated using Cox proportional hazards regression.	Up to 10 years from randomization
Impact of OAR-Driven Nodal Dose De-Escalation	Assessment of the impact of protocol-defined organ-at-risk-driven nodal dose de-escalation on regional nodal control and treatment-related toxicity.	Up to 10 years from randomization
Interaction Effect Between Radiotherapy Intensification and Systemic Therapy Intensification	Interaction term between radiotherapy intensification strategy (prostate-first vs combined prostate and nodal dose escalation) and systemic therapy intensification (androgen deprivation therapy with or without androgen receptor pathway inhibitors) evaluated in Cox proportional hazards models for metastasis-free survival. Reported as hazard ratio with interaction p-value.	Up to 10 years from randomization
Hazard Ratio for Metastasis-Free Survival per 10 Gy Increase in Delivered Nodal EQD2	Hazard ratio for metastasis-free survival associated with each 10 Gy increase in delivered pelvic nodal EQD2 (α/β = 1.5), estimated using Cox proportional hazards regression.	From randomization up to 10 years

Collaborators and Investigators

• Sponsor: Affidea Nu-med Center of Oncological DIagnostics and Therapy
• Investigators: Principal Investigator: Mateusz Bilski, MD, PhD, Affidea Nu-med Center of Oncological DIagnostics and Therapy

Publications and helpful links

General Publications

• Hofman MS, Lawrentschuk N, Francis RJ, Tang C, Vela I, Thomas P, Rutherford N, Martin JM, Frydenberg M, Shakher R, Wong LM, Taubman K, Ting Lee S, Hsiao E, Roach P, Nottage M, Kirkwood I, Hayne D, Link E, Marusic P, Matera A, Herschtal A, Iravani A, Hicks RJ, Williams S, Murphy DG; proPSMA Study Group Collaborators. Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA): a prospective, randomised, multicentre study. Lancet. 2020 Apr 11;395(10231):1208-1216. doi: 10.1016/S0140-6736(20)30314-7. Epub 2020 Mar 22.
• Onishi M, Imajo Y, Yamaguchi S, et al. Intensity-modulated radiotherapy with simultaneous integrated boost for clinically node-positive prostate cancer. Cancers (Basel). 2021;13(15):3868. doi:10.3390/cancers13153868.
• Onal C, Torun N, Karakaya M, et al. Ga-68-PSMA-PET/CT response in pelvic node-positive prostate cancer after definitive radiotherapy: Prognostic implications. Int J Radiat Oncol Biol Phys. 2025;00:1-10.
• Menne Guricová K, Draulans C, Pos FJ, et al. Focal boost to the intraprostatic tumor in external beam radiotherapy for patients with localized prostate cancer: 10-year outcomes of the FLAME trial. J Clin Oncol. 2025;43(28):3065-3069. doi:10.1200/JCO-25-00274.
• Attard G, Murphy L, Clarke NW, et al. Abiraterone acetate and prednisolone with or without enzalutamide for high-risk non-metastatic prostate cancer: Primary results of STAMPEDE phase 3 trials. Lancet. 2022;399(10323):447-460. doi:10.1016/S0140-6736(21)01607-0.
• De Hertogh, Olivier et al. Consensus Delineation Guidelines for Pelvic Lymph Node Radiation Therapy of Prostate Cancer: On Behalf of the Francophone Group of Urological Radiation Therapy (GFRU). International Journal of Radiation Oncology, Biology, Physics, Volume 118, Issue 1, 29 - 40.
• Gaber CE, Bernstein AN, Parikh RB, et al. Real-world cardiovascular safety of abiraterone vs enzalutamide in prostate cancer. J Geriatr Oncol. 2025;16(5):101585.
• Lee YHA, Lin HC, Liao KM, et al. Major adverse cardiovascular events of enzalutamide versus abiraterone in prostate cancer: A comparative risk study. Prostate Cancer Prostatic Dis. 2024;27(6):1080-1089.
• Liu Y, Zhang X, Wang Y, et al. Cardiovascular adverse events associated with new hormonal agents for prostate cancer: A FAERS pharmacovigilance analysis. Clin Genitourin Cancer. 2023;21(6):e489-e500.
• Nilsson, Per et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for localised prostate cancer (HYPO-RT-PC): 10-year outcomes of an open-label, randomised, phase 3, non-inferiority trial. The Lancet Oncology. 2026 February 05; Volume 0, Issue 0. doi: 10.1016/S1470-2045(25)00656-4
• Tang T, Rodrigues G, Warner A, Bauman G. Long-Term Outcomes Following Fairly Brief Androgen Suppression and Stereotactic Radiation Therapy in High-Risk Prostate Cancer: Update From the FASTR/FASTR-2 Trials. Pract Radiat Oncol. 2024 Jan-Feb;14(1):e48-e56. doi: 10.1016/j.prro.2023.08.006. Epub 2023 Oct 3. PMID: 37791942.
• Pommier P, Chabaud S, Lagrange JL, et al. Pelvic irradiation in localized prostate adenocarcinoma: Final results of GETUG-01. Int J Radiat Oncol Biol Phys. 2007;69(3):646-653.
• Roach M III, DeSilvio M, Lawton C, et al. Whole-pelvic versus prostate-only radiotherapy with neoadjuvant versus adjuvant ADT (RTOG 94-13). J Clin Oncol. 2003;21(10):1904-1911.
• Hall WA, Straka C, Kim E, et al. Long-term outcomes of dose-escalated pelvic lymph node IMRT for prostate cancer. Int J Radiat Oncol Biol Phys. 2021;109(4):957-968. doi:10.1016/j.ijrobp.2020.09.036.
• Tsuchida T, et al. Dose-response relationship in definitive radiation therapy for pelvic lymph node-positive prostate cancer: A multicenter retrospective analysis. Prostate Cancer Prostatic Dis. 2025;28(3):123-132. doi:10.1038/s41391-025-00976-7.
• Bilski M, Mastroleo F, Chyrek AJ, et al. Outcomes of radiotherapy with or without dose escalation to lymph node metastases detected by PSMA-PET or conventional imaging in node-positive prostate cancer (PRIMENOD). Unpublished manuscript; 2025.
• Maebayashi T, Mizowaki T, Ishikawa H, Nakamura K, Inaba K, Asakura H, Iwata H, Itasaka S, Wada H, Sakaguchi M, Jingu K, Akiba T, Tomita N, Nakamura K; Japanese Radiation Oncology Study Group. Prostate dose escalation may positively impact survival in patients with clinically node-positive prostate cancer definitively treated by radiotherapy: surveillance study of the Japanese Radiation Oncology Study Group (JROSG). J Radiat Res. 2025 Mar 24;66(2):157-166. doi: 10.1093/jrr/rraf005.
• Bilski M, Lelek P, Stankiewicz M, Miszczyk M, Burchardt W, Kluska A, Napieralska A, Kukielka A, Cisek P, Konat-Baska K, Stando R, Dec M, Piliszczuk E, Matys R, Bajon T, Trojanowski M, Moll M, Gomez-Iturriaga A, Chichel A, Wojcieszek P, Shariat SF, Chyrek AJ. MUlticentre REtrospective comparison of definitive EBRT with or without HDR BRAchytherapy boost in patients with locally-advanced prostate cancer and regional lymph NOde metastases (MUREBRANO) - A propensity score matched analysis. Radiother Oncol. 2025 Nov;212:111112. doi: 10.1016/j.radonc.2025.111112. Epub 2025 Aug 27.
• National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines in Oncology: Prostate Cancer. Version 2025. Available at: https://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf
• Walz J, Attard G, Bjartell A, Blanchard P, Castro E, Comperat E, Emmett L, Fanti S, Fonteyne V, Foulon S, Gillessen S, Gravis G, James ND, Oprea-Lager DE, Ost P, Padhani A, Parker C, Renard-Penna RM, Rubin MA, Saad F, Sweeney C, Tilki D, Tombal B, Tree AC, Zilli T, Fizazi K; ESMO Guidelines Committee. Electronic address: clinicalguidelines@esmo.org. Local and locoregional prostate cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Ann Oncol. 2025 Dec 18:S0923-7534(25)06330-6. doi: 10.1016/j.annonc.2025.12.009. Online ahead of print. No abstract available.
• EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer. 2025 Update. EAU Guidelines Office, Arnhem, The Netherlands; 2025.

Study record dates

Study Major Dates

• Study Start (Actual): March 19, 2026
• Primary Completion (Estimated): December 1, 2033
• Study Completion (Estimated): December 1, 2035

Study Registration Dates

• First Submitted: February 10, 2026
• First Submitted That Met QC Criteria: February 15, 2026
• First Posted (Actual): February 23, 2026

Study Record Updates

• Last Update Posted (Actual): March 23, 2026
• Last Update Submitted That Met QC Criteria: March 19, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: Radiotherapy; Brachytherapy; SBRT; Metastases; Dose Escalation; Stereotactic Body Radiotherapy; PSMA PET; Prostate-Specific Membrane Antigen; High-Dose-Rate Brachytherapy; Ultrahypofractionation; Low-Dose-Rate Brachytherapy; Metastasis-Free Survival; Nodal metastases
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Pathologic Processes; Genital Neoplasms, Male; Urogenital Neoplasms; Neoplasms by Site; Neoplasms; Genital Diseases, Male; Prostatic Diseases; Male Urogenital Diseases; Neoplastic Processes; Pathological Conditions, Signs and Symptoms; Prostatic Neoplasms; Neoplasm Metastasis; Physiological Effects of Drugs; Hormones, Hormone Substitutes, and Hormone Antagonists; Hormone Antagonists; Pharmacologic Actions; Chemical Actions and Uses; Androgen Antagonists
• Other Study ID Numbers: PRO-BOOST-N

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data (IPD) underlying the results reported in primary and secondary publications will be shared. This includes baseline demographic and clinical characteristics, treatment allocation, radiotherapy and systemic treatment variables, outcome measures, and safety data necessary to reproduce the main analyses.
• IPD Sharing Time Frame: IPD and supporting information will be available beginning 12 months after publication of the primary study results and will remain available for a period of 5 years thereafter.
• IPD Sharing Access Criteria: Access to de-identified IPD will be granted to qualified researchers for approved research purposes following submission of a written proposal. Requests will be reviewed by the study steering committee for scientific merit, feasibility, and ethical appropriateness. A data use agreement will be required prior to data access.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No