In a long-term follow-up of the phase II SABR-COMET trial reported in the Journal of Clinical Oncology, David A. Palma, MD, PhD, and colleagues found that the addition of stereotactic ablative radiotherapy (SABR) to palliative standard-of-care treatment in patients with oligometastatic cancers resulted in a markedly greater overall survival rate at 5 years, with the magnitude of benefit being greater than that in the initial analysis of the trial.
“With extended follow-up, the impact of SABR on overall survival was larger in magnitude than in the initial analysis and durable over time. There were no new safety signals, and SABR had no detrimental impact on quality of life.”— David A. Palma, MD, PhD, and colleagues
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The initial report from SABR-COMET showed a 13-month improvement in median overall survival in patients receiving SABR at median follow-up of 28 months.
Study Details
In the international open-label trial, 99 patients with a controlled primary tumor and one to five metastases amenable to SABR were randomly assigned 2:1 between February 2012 and August 2016 to receive SABR and palliative standard-of-care treatments (n = 63) or standard-of-care treatments alone (n = 33). Randomization was stratified by number of metastases (1–3 vs 4/5 [8% vs 6% of patients]). The most common primary tumor types included in the trial were breast (n = 18), lung (n = 18), colorectal (n = 18), and prostate (n = 16). The primary endpoint was overall survival, with P ≤ .20 indicating a positive trial.
Key Findings
For the current analysis, median follow-up was 51 months.
- Palliative systemic therapy was used in 55% of the SABR group vs 64% of the standard-of-care group (P = .39). Palliative radiotherapy was used in 24% vs 70% (P < .001).
- At time of analysis, death had occurred in 53% vs 73% of patients. Median overall survival was 50 months vs 28 months (hazard ratio [HR] = 0.47, P = .006). Overall survival at 5 years was 42.3% vs 17.7%.
- Median progression-free survival was 11.6 months vs 5.4 months (HR = 0.48, P = .001). Progression-free survival at 4 and 5 years was 21.6% vs 3.2% and 17.3% vs 0%, respectively.
- No differences between groups in total quality of life scores or subscale scores were observed over time on Functional Assessment of Cancer Therapy: General assessment.
- No new grade ≥ 2 adverse events were observed since the initial analysis. At initial analysis, grade ≥ 2 adverse events had occurred in 29% vs 9% of patients, and three patients in the SABR group (4.5%) had died from adverse events considered at least possibly related to treatment.
The investigators concluded, “With extended follow-up, the impact of SABR on overall survival was larger in magnitude than in the initial analysis and durable over time. There were no new safety signals, and SABR had no detrimental impact on quality of life.”
Dr. Palma, of the London Health Sciences Centre, London, Ontario, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Ontario Institute for Cancer Research and London Regional Cancer Program. For full disclosures of the study authors, visit ascopubs.org.
