Stereotactic Radiotherapy Versus Palliative Conventional Radiotherapy for Oligoprogressive Metastatic Cancers

Stereotactic Radiotherapy Versus Palliative Conventional Radiotherapy for Oligoprogressive Metastatic Cancers: A Double-Blind Randomized Phase III Trial

STOP-2 is a phase III multi-institutional double-blind randomized trial. 194 participants will be enrolled in this trial. Participants will be randomized in a 1:1 ratio between the Control Arm vs. the Experimental Arm.

Participants, enrolling oncologists, and the statistician will be blinded to trial arm assignment.

In the control arm, radiotherapy will consist of 8 Gy in 1 fraction to all sites of oligoprogression, and the experimental arm will consist of SABR treatment to all sites of oligoprogression.

Primary Objectives

• To assess the impact of SABR, compared to palliative conventional radiotherapy, on Progression-free survival on next line systemic therapy (PFS-NEST), oncologic outcomes, and Quality of Life (QOL) in participants with 1-5 oligoprogressing lesions.
• To assess the feasibility of the clinical trial in terms of accrual and success of double-blinding.

Secondary Objectives

• To evaluate and compare the impact of SABR and palliative radiation therapy on the overall survival (OS), progression free survival (PFS), polymetastatic progression-free survival (PPFS);
• To assess and compare the proportion of participants receiving additional radiation therapy and other metastasis-directed interventions during follow-up between both arms;
• To compare the impact of SABR and palliative radiation therapy on the time to initiation of the next line of systemic therapy;
• To identify and compare the anatomic sites of disease progression between the experimental (SABR) and control (palliative radiation) arms;
• To compare the treatment related toxicity among participants in each arm;
• To evaluate and compare the quality of life among participants in each arm;
• To assess the cost-effectiveness of the experimental arm compared to the control arm.

Study Overview

• Status: Recruiting
• Conditions: Oligometastatic Disease; Oligoprogression; OligoProgressive Metastatic Disease
• Intervention / Treatment: Radiation: Palliative radiotherapy; Radiation: Stereotactic ablative radiotherapy (SABR)

• Study Type: Interventional
• Enrollment (Estimated): 194
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sarah Baker, MD, PhD, FRCPC; Phone Number: 604-930-4032; Email: sarah.baker1@bccancer.bc.ca
• Study Contact Backup: Name: Narsis Afghari, MSc.; Phone Number: 203838 604-675-4100; Email: narsis.afghari@bccancer.bc.ca

Study Locations

• Canada
  • British Columbia
    • Surrey, British Columbia, Canada, V3V 1Z2
      • Recruiting
      • BC Cancer - Surrey
      • Contact: Sarah Baker, MD, PhD, FRCPC; Phone Number: 604-930-4032; Email: sarah.baker1@bccancer.bc.ca

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

1. Age 19 or older
2. Able to provide informed consent
3. Histologically confirmed solid malignancy (excluding lymphoma or myeloma) with metastatic disease detected on imaging
4. Biopsy of metastasis at some time prior to enrollment is preferred, but not required
5. ECOG performance status 0-2
6. Life expectancy ≥ 6 months

7. Progression meeting RECIST criteria in up to 5 individual lesions. Progression may be defined as:

   1. Progression of an individual metastasis according to RECIST 1.1 criteria (≥ 20% enlargement of the tumour vs. baseline or nadir, taking as reference the smallest diameter seen prior to starting or during systemic therapy, and associated with a 5 mm minimum increase in size) OR
   2. Unambiguous development of a new metastatic lesion at least 5 mm in size OR
   3. Progressive enlargement of a known metastasis on 2 consecutive imaging studies 2-3 months apart with a minimum 5 mm increase in size from baseline.
   4. A progressing primary tumor is eligible as per the criteria above

8. If the participant is on systemic therapy at the time of oligoprogression:

   The most recent systemic therapy agent must have been delivered for a total of at least 3 months, with an initial partial response (PR), complete response (CR) or stable disease (SD) prior to the development of oligoprogressive lesions

9. If the participant is not on systemic therapy at the time of oligoprogression:

   (i.e., "oligorecurrence"(1), however, included as "oligoprogression" for the purpose of this study protocol):

10. There must be PR, CR or SD persisting for at least 3 months prior to the development of oligoprogressive lesions
11. Participants who are not on systemic therapy at the time of oligoprogression must have other site(s) of disease (metastases or primary tumor) that are stable or resolved and have not received definitive treatment (inclusive of surgery, radical doses of radiotherapy including SABR, or ablation) and are not going to receive SABR.
12. All sites of oligoprogression can be safely treated
13. Restaging completed within 12 weeks prior to randomization (see section 5.1)
14. Negative urine pregnancy test for People of Child-Bearing Potential (POCBP) within 4 weeks of radiotherapy start date.

Exclusion Criteria:

1. Serious medical comorbidities precluding radiotherapy. These include ataxia-telangiectasia or scleroderma, Crohn's disease in participants where the gastrointestinal (GI) tract will receive radiotherapy, or ulcerative colitis where the bowel will receive radiotherapy.

   a. For participants with oligoprogressive lesions in the lung or thorax, this includes interstitial lung disease.

2. Substantial overlap with a previously treated radiation volume. Prior radiotherapy in general is allowed, provided that the composite plan meets dose constraints herein. For participants treated with radiation previously, biological effective dose calculations should be used to equate previous doses to the tolerance doses listed in Appendix 1. A tissue recovery factor may be used in these calculations and if so, must be clearly documented, along with elapsed time from previous radiotherapy, and approved by the local principal investigator.
3. Current malignant pleural effusion, malignant ascites, or leptomeningeal disease
4. Inability to treat all sites of oligoprogressive disease
5. Liver metastases requiring placement of fiducial markers for SABR, as this would compromise successful blinding. Liver metastases are eligible if: 1) they are treated at an institution that offers liver SABR without fiducial markers or 2) pre-existing markers such as surgical clips or calcifications would serve as fiducial markers
6. Brain metastasis > 3.5 cm in size or a total volume of brain metastases greater than 30 cc.
7. Clinical or radiologic evidence of spinal cord compression. Participants can be eligible if surgical resection has been performed.
8. Participants with spine instability as judged by a Spinal Instability Neoplastic Score (SINS) of >12.
9. Dominant brain metastasis requiring surgical decompression
10. For participants with liver metastases; moderate/severe liver dysfunction (Child Pugh B or C)
11. Liver metastases located in the "Biliary no fly zone" defined for this trial as common biliary track, cystic duct and distal branches (1 cm) + 5 mm
12. Surgical resection of all oligoprogression metastases (i.e. no lesion available to be treated with SABR)
13. Pregnant or lactating individuals

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Control Arm (Palliative Radiotherapy)	Radiation: Palliative radiotherapy; Radiotherapy will consist of 8 Gy in 1 fraction to all sites of oligoprogression. Participants will continue their current systemic therapy (if already on systemic therapy at the time of oligoprogression event) or continue off systemic therapy (if the participant was not on systemic therapy at the time of the oligorecurrence event).
Experimental: Experimental Arm (SABR)	Radiation: Stereotactic ablative radiotherapy (SABR); SABR is a safe and effective modality for metastasis-directed therapy, delivering a high dose of radiotherapy to a small target using conformal techniques. Emerging evidence suggests that SABR for oligoprogressive cancer may extend the duration of systemic therapy, and result in improvements in Progression Free Survival (PFS) and Overall Survival (OS) compared to historic controls.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Progression-Free Survival on Next Line Systemic Therapy (PFS-NEST)	Time from randomization to progression (RECIST criteria) beyond next line of systemic therapy or death from any cause or date of last follow-up, whichever occurs first. Next line systemic therapy is the first new systemic therapy initiated after documented disease progression	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Evaluation of feasibility of the clinical trial in terms of successful accrual	Accrual will be measured by the number of participants enrolled in the trial within the specified time frame.	12 and 24 months
Evaluation of feasibility of the clinical trial in terms of success of double-blinding	The success of double-blinding will be measured by providing both the participant and oncologist with a blinding questionnaire asking them to select the suspected trial arm assignment (options include palliative arm, SABR arm, or unknown).	6 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Evaluation of OS, PFS, and PPFS	To evaluate and compare the impact of SABR and palliative radiation therapy on the overall survival (OS), progression free survival (PFS), polymetastatic progression-free survival (PPFS);	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Time to next line systemic therapy	To assess and compare the proportion of participants receiving additional radiation therapy and other metastasis-directed interventions during follow-up between both arms;	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Comparing the anatomic sites of disease progression	A list of anatomical sites at which there are new or progressing lesions will be collected	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Evaluation of the treatment related toxicities	Assessed by the Common Terminology Criteria for Adverse Events (CTCAE) version 5 for each organ treated (e.g., liver, lung, bone)	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Comparing the quality of life among participants in each arm using Functional Assessment of Cancer Therapy: General (FACT-G)	Quality of life will be assessed with the FACT-G questionnaire. The FACT-G score ranges from 0 to 108, with higher scores indicating a better quality of life.	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Comparing the quality of life among participants in each arm using EuroQol 5-Dimension 5-Level (EQ-5D-5L)	Quality of life will be assessed with the EQ-5D-5L questionnaire. The EQ-5D-5L index score ranges from -0.224 to 1, with higher scores indicating a better quality of life.	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Comparing cost-effectiveness of the arms using the resource utilization forms	Costs associated with each treatment arm will be measured using resource utilization forms.	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Comparing cost-effectiveness of the arms using the EQ-5D-5L	Costs associated with each treatment arm will be measured using EQ-5D-5L	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Evaluation of Tumor Response Rate (TRR) using RECIST Criteria	Tumor response rate will be assessed using RECIST criteria.	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months
Evaluation of Quality of Life (QOL) using European Organization For Research And Treatment Of Cancer (EORTC QLQ-C30) Questionnaire	Health-related quality of life will be measured using the EORTC QLQ-C30 questionnaire, covering physical functioning, emotional functioning, and symptom scales. This questionnaire consists of 30 items, and the score range is 0-100. On this scale, a higher score indicates a higher (better) level of functioning or a higher (worse) level of symptoms, depending on the type of scale.	3 months, 6 months, 12 months, 15 months, 18 months, 21 months, 24 months, 36 months, 42 months, 48 months, 54 months, 60 months

Collaborators and Investigators

• Sponsor: British Columbia Cancer Agency

Study record dates

Study Major Dates

• Study Start (Actual): December 4, 2025
• Primary Completion (Estimated): June 1, 2030
• Study Completion (Estimated): June 1, 2033

Study Registration Dates

• First Submitted: March 10, 2025
• First Submitted That Met QC Criteria: April 7, 2025
• First Posted (Actual): April 9, 2025

Study Record Updates

• Last Update Posted (Actual): December 15, 2025
• Last Update Submitted That Met QC Criteria: December 8, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Quality of life; Radiotherapy; Metastatic Cancer; SABR
• Additional Relevant MeSH Terms: Pathologic Processes; Neoplasms; Neoplastic Processes; Pathological Conditions, Signs and Symptoms; Neoplasm Metastasis
• Other Study ID Numbers: STOP-2

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
• product manufactured in and exported from the U.S.: No