According to the oligometastatic paradigm, patients with a limited number of metastatic lesions can be amenable to curative treatment if all lesions are resected or ablated using stereotactic ablative radiotherapy (SABR). Most of the evidence supporting this paradigm is from observational studies, but now the results of a randomized phase II trial indicate that SABR improves overall survival (OS) in these patients.
In the SABR-COMET trial, 99 patients with a controlled primary solid tumour and 1–5 metastatic lesions were randomly allocated to receive standard-of-care palliative treatment alone (control; n = 33) or in addition to SABR delivered to all metastatic lesions (n = 66).
Median OS was longer with SABR than with no ablative treatment: 41 months versus 28 months (HR 0.57, 95% CI 0.30–1.10; P = 0.09). “We used a randomized phase II trial screening design, and thus a P value ≤0.2 for OS indicates a positive result,” explains lead investigator David Palma.
Median progression-free survival was also longer with SABR: 12.0 months versus 6.0 months (HR 0.47, 95% CI 0.30–0.76; P = 0.0012). The percentage of patients with control of all lesions that were present at randomization was 75% for patients receiving SABR versus 49% with no ablative treatment (P = 0.001). No significant differences were observed in quality-of-life scores (measured with the FACT-G tool).
The incidence of grade ≥2 treatment-related adverse events (AEs) was higher with SABR: 29% versus 9% (P = 0.026). Of note, 3 patients in the SABR group and none in the control group died from treatment-related toxicities.
In summary, evidence from a randomized trial now supports a survival benefit from SABR in oligometastatic disease. “We want to prove this benefit in two follow-up phase III trials: the ongoing SABR-COMET-10 (NCT03721341), which involves patients with 4–10 metastatic lesions, and SABR-COMET-3 (NCT03862911), which is expected to open in 2–3 months and involves patients with 1–3 metastatic lesions,” comments Palma.
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Palma, D. A. et al. Stereotactic ablative radiotherapy versus standard of care palliative treatment in patients with oligometastatic cancers (SABR-COMET): a randomised, phase 2, open-label trial. Lancet https://doi.org/10.1016/S0140-6736(18)32487-5 (2019)
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Romero, D. SABR improves outcomes. Nat Rev Clin Oncol 16, 402 (2019). https://doi.org/10.1038/s41571-019-0217-1
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DOI: https://doi.org/10.1038/s41571-019-0217-1
