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Off-Protocol Radiation Therapy in Phase 3 Metastatic Solid Tumor Trials.
Alexander D Sherry1, Timothy A Lin2, Zachary R McCaw3
1Department of Radiation Oncology, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
International Journal of Radiation Oncology, Biology, Physics
|October 1, 2024
Summary
Most phase 3 trials permit off-protocol radiation therapy, but its impact on systemic therapy outcomes is understudied. Few trials report utilization, and those allowing it may be more likely to meet primary endpoints.
Area of Science:
- Oncology
- Clinical Trials
- Radiation Oncology
Background:
- Radiation therapy, especially ablative radiation therapy, may alter the course of metastatic disease.
- Off-protocol radiation therapy in systemic therapy trials can potentially influence study endpoints.
Purpose of the Study:
- To determine the frequency of off-protocol radiation therapy allowance and utilization in phase 3 systemic therapy trials.
- To investigate the correlation between off-protocol radiation therapy and study outcomes.
Main Methods:
- Screened 112 two-arm, superiority-design, phase 3 randomized trials from ClinicalTrials.gov (2010-2019).
- Assessed trial protocols for off-protocol radiation therapy policies.
- Used logistic regression to calculate adjusted odds ratios for outcome correlation.
Main Results:
- Off-protocol radiation therapy was allowed in 52% of trials, not discussed in 25%, and prohibited in 23%.
- Only 2% of trials reported utilization rates; ablative radiation therapy use was not detailed.
- Trials permitting off-protocol radiation therapy were more likely to meet primary endpoints in open-label studies (aOR, 4.50).
Conclusions:
- Most phase 3 systemic therapy trials allow off-protocol radiation therapy.
- The influence of off-protocol radiation therapy, particularly ablative forms, on study outcomes remains largely unevaluated.
