External Beam and Radioligand Radiotherapy for mCRPC (ARREST)

August 28, 2026 updated by: Centre hospitalier de l'Université de Montréal (CHUM)

Adaptive External Beam and Radioligand Radiotherapy for MEtaSTatic Castration Resistant Prostate Cancer (ARREST): a Phase II Registry-based RCT

Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy with Lutetium-177 (¹⁷⁷Lu-PSMA) is an established treatment for metastatic prostate cancer. Administered intravenously, it enables targeted irradiation of PSMA-expressing tumor cells. However, 30-50% of patients derive limited benefit. This variability could be partly explained by heterogeneity in delivered dose across lesions, leading to under-treatment of certain metastases. The addition of targeted external beam radiotherapy (EBRT) may compensate for this underdosing by delivering a precise dose to insufficiently irradiated lesions.

The investigators hypothesize that the addition of adaptive EBRT to ¹⁷⁷Lu-PSMA will reduce the incidence of skeletal-related events (pathologic fracture, spinal cord compression, surgery, or palliative radiotherapy) without increasing toxicity.

Adaptive EBRT and RLT for mCRPC (ARREST) is a pragmatic registry-based phase 2, multi-center randomized controlled trial within the PERa prospective cohort (NCT03378856) planned to activate in 2026. Patients receiving standard-of-care (SOC) ¹⁷⁷Lu-PSMA with targetable metastatic burden identified on imaging and suitable for EBRT will be eligible. One hundred and twenty eligible patients will be randomized 1:1 to receive either SOC ¹⁷⁷Lu-PSMA therapy alone (maximum 6 cycles) or combined ¹⁷⁷Lu-PSMA plus adaptive EBRT. Patients in the experimental arm will undergo FDG-PET at study entry and SPECT-CT after each cycle of radioligand therapy. Lesions selected for EBRT boost will be chosen based on a set of criteria that include estimated suboptimal absorbed dose from ¹⁷⁷Lu-PSMA, lesions demonstrating low PSMA but high FDG uptake, symptomatic lesions, and lesions at high risk for skeletal-related events. Selected lesions will receive single-fraction EBRT. The prescribed dose will range from 6-12 Gy, with the goal of achieving a combined total biological effective dose of ≥50 Gy (α/β = 5), while prioritizing dose limits for organs at risk.

A maximum treatment time of 60 minutes is permitted for each adaptive EBRT treatment. Patients in the experimental arm who achieve a complete response, as measured by ¹⁷⁷Lu-SPECT-CT and PSA, will pause ARREST treatment and resume at disease progression. The primary endpoint is skeletal-related events at 1 year. Secondary objectives include overall survival, ¹⁷⁷Lu-SPECT-CT and PSA response, toxicity, and quality of life. The sample size is designed to detect a 12-month improvement in the rate of skeletal-related events with a hazard ratio of 0.61, a one-sided alpha of 0.1, and 80% power.

ARREST is expected to safely optimize tumor dose, offering a personalized hybrid approach that may lead to improved patient outcomes. In addition, this study will permit further understanding of these two distinct radiation delivery methods and their effects on tissues, thereby refining the relative biological effectiveness model for more precise treatment planning.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

120

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Receiving 177Lu-PSMA for mCRPC
  • ECOG 0-1
  • Presence of a discernible metastatic burden suitable for EBRT
  • Receiving bone protective therapy

Exclusion Criteria:

  • no exclusions

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Standard of care 177Lutetium-PSMA
Radiation: Standard of care 177Lutetium-PSMA
Per Standard of care
Experimental: EBRT + 177Lutetium-PSMA
Radiation: External Beam Radiotherapy Delivered Between Cycles of Radioligand Radiotherapy
Adaptive EBRT dose based on 177Lutetium dosimetry

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Skeletal Related Events
Time Frame: 12 months
12 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Adverse Events
Time Frame: 12 months
CTCAE Grade 2+ events
12 months
Overall suvival
Time Frame: 24 months
24 months
PSA Response
Time Frame: week 12
Proportion of patients achieving a >'50% PSA decline
week 12
CR/PR on SPECT-CT
Time Frame: After 3 cycles
After 3 cycles
Quality of Life Questionnaires
Time Frame: 12 and 24 months
EORTIC QLQ-C30, PRO-CTCAE
12 and 24 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Centre hospitalier de l'Université de Montréal (CHUM)

Collaborators

Varian, a Siemens Healthineers Company

Investigators

  • Principal Investigator: Cynthia Menard, MD, Centre Hospitalier de l'Universite de Montreal (CHUM)

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 7, 2026

Primary Completion (Estimated)

May 1, 2028

Study Completion (Estimated)

May 1, 2028

Study Registration Dates

First Submitted

November 17, 2025

First Submitted That Met QC Criteria

January 12, 2026

First Posted (Actual)

January 21, 2026

Study Record Updates

Last Update Posted (Actual)

September 1, 2026

Last Update Submitted That Met QC Criteria

August 28, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • 2026-13179

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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