Adaptive Fractionation in Online Adaptive Stereotactic Radiotherapy for Abdominopelvic Lymph Node Oligometastases (STEAL-3)

Oligometastases, a state of cancer with up to five metastases, was traditionally treated with systemic treatments like chemotherapy. Treatment with stereotactic body radiotherapy (SBRT) showed a high local control and improved disease-free survival.

The use of SBRT also allows for the deferral of systemic treatment, thereby delaying its potential side effects. SBRT enables the delivery of a high dose to the tumor while minimizing the dose to organs at risk, reducing normal tissue damage, however, toxicity remains a potential issue in the abdominopelvic region, where lymph node oligometastases are often located near highly mobile, radiosensitive organs like the bowel.

Online adaptive radiotherapy is used to address this issue, adapting the treatment plan to the anatomy of the day. Unfortunately, adaptive radiotherapy results in longer treatment delivery times than conventional radiotherapy. This can potentially be countered by increasing the fraction dose and reducing the number of fractions if the patient anatomy allows it. This is convenient for the patient as it reduces the number of hospital visits, and it could also reduce the total workload for the hospital.

Therefore, there is not only a benefit of a reduction in toxicity by adaptive treatment, but also in reducing the total treatment time. This study aims to investigate if the number of adaptive fractions can be reduced by 30% for patients with abdominal or pelvic lymph node oligometastases.

Study Overview

• Status: Recruiting
• Conditions: Lymph Node Oligometastases
• Intervention / Treatment: Radiation: Online-Adaptive SBRT

• Study Type: Interventional
• Enrollment (Estimated): 25
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Netherlands
  • South Holland
    • Rotterdam, South Holland, Netherlands, 3015GD
      • Recruiting
      • Erasmus MC
      • Contact: E. van Lieshout, MSc.; Phone Number: +31107041538; Email: e.vanlieshout.2@erasmusmc.nl

Participation Criteria

Eligibility Criteria

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

Description

Inclusion criteria:

• Patients with abdominal and/or pelvic lymph node recurrences of solid tumors.
• No more than 5 metastatic lesions in no more than 2 organs and a controlled primary tumor site.
• Diagnostic imaging includes at least a PET scan or CT thorax/abdomen, of which one is not older than 4 weeks at the time of referral for SBRT.
• Primary tumor must be treated at least 4 months before the diagnosis of metastasis.
• Patients must be 18 years or older.
• Written informed consent.

Exclusion criteria:

• Prior radiotherapy in the same field.
• Second primary malignancy except in situ carcinoma of the cervix, adequately treated non-melanoma skin cancer, or other malignancy treated at least 3 years.
• Serious concomitant systemic disorders that would compromise the safety of the patient or his/her ability to complete the study, at the discretion of the investigator.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Online-Adaptive SBRT

Radiation: Online-Adaptive SBRT; The treatment will consist of online-adaptive SBRT using the ETHOS linear accelerator. The standard treatment will be 45 Gy in 5 fractions (45Gy/5Fx). If the patient anatomy allows, the number of planned fractions will be isotoxically reduced, keeping OAR and target dose goals biologically equivalent, to a minimum of 25 Gy in 1 fraction (25Gy/1Fx). For the adaptive treatment, daily HyperSight CBCT scans will be made, and the target and OAR contours will be automatically delineated and adjusted if necessary. If, during treatment, patient anatomy changes in such a way that fewer or more fractions are required than planned, changes can be made in the daily dose and number of remaining fractions. During and after treatment, a CBCT scan is made to verify the current treatment and improve future treatments.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of participants achieving ≥30% reduction in number of online-adaptive fractions compared with the standard 5-fraction SBRT course.	For each participant, the number of online-adaptive fractions actually delivered will be recorded. The reduction will be calculated as: (standard - delivered) / standard * 100%.	From enrollment to the end of treatment at 1 month.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Overall survival (time-to-event in months) from start of SBRT	Time from first SBRT fraction to death from any cause; participants alive at analysis are censored at the date last known alive.	From first day of treatment up to 48 months.
Local control at the treated site assessed by RECIST v1.1	Proportion of treated lesions without local progression per RECIST v1.1 on protocol imaging.	At 12, 24, and 36 months after treatment.
Participants with treatment-related acute adverse events (CTCAE v5.0)	Number of participants with any treatment-related adverse event per CTCAE v5.0 occurring during treatment or within 90 days after the last fraction.	From first day of treatment to 90 days after last fraction.
Participants with treatment-related late adverse events (CTCAE v5.0)	Number of participants with any treatment-related adverse event per CTCAE v5.0 occurring >90 days after the last fraction.	>90 days after last fraction to 24 months.
Magnitude of intra- and interfraction bowel displacement on CBCT (mm)	Displacement quantified on daily CBCT as (a) intrafraction shift between pre- and post-treatment CBCT and (b) interfraction shift between consecutive pre-treatment CBCTs. Summaries will include, but are not limited to: per-fraction mean and maximum displacement per participant.	Assessed at each delivered fraction from the first fraction through the final delivered fraction (up to 5 fractions over up to 2 weeks).
Treatment fractions requiring patient re-alignment due to intrafraction motion (CBCT-guided adaptive workflow)	Number of delivered fractions in which treatment is paused and patient re-aligned based on the surface scanning system guidance criteria defined in the clinical workflow.	Assessed at each delivered fraction from the first fraction through the final delivered fraction (up to 5 fractions over up to 2 weeks).

Collaborators and Investigators

• Sponsor: Joost J. M. E. Nuyttens

Study record dates

Study Major Dates

• Study Start (Actual): February 27, 2025
• Primary Completion (Actual): February 5, 2026
• Study Completion (Estimated): January 1, 2028

Study Registration Dates

• First Submitted: January 12, 2026
• First Submitted That Met QC Criteria: February 12, 2026
• First Posted (Actual): February 17, 2026

Study Record Updates

• Last Update Posted (Actual): February 17, 2026
• Last Update Submitted That Met QC Criteria: February 12, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: NL-OMON57107

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 of this study will be shared with qualified researchers. All shared data will be coded and stripped of personal health information (PHI). Approval of the data request and execution of all required agreements (e.g., Data Sharing Agreement) will be required prior to release.
• IPD Sharing Time Frame: Data requests may be submitted starting 12 months after publication, and data will remain available for 24 months thereafter. Requests for extensions will be considered on a case-by-case basis.

IPD Sharing Access Criteria

Access will be granted to qualified researchers conducting ethically approved, scientifically sound studies. Requests must include:

• A brief research proposal describing objectives and methods
• (If applicable) A Statistical Analysis Plan
• Documentation of ethical approval
• Agreement to sign a Data Sharing Agreement

• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE; CSR

Drug and device information, study documents

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