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Top Line: We’ve seen a big shift in how we view low-volume metastatic disease since abstract reporting of SABR-COMET a couple of years ago and its initial publication last year.
The Study: What’s left? Long-term reporting with 5-year survival rates. That’s right, half a decade out, which should be telling enough. Once again for good measure, this phase 2 trial included 99 patients with 1-3 (n= 92) or up to 4-5 (n= 7) mets from any cancer without progression at the primary site at least 3 months after definitive treatment. Whereas the previously-reported discrepancy in median survival times was impressive with an improvement from 28 → 41 months, longer follow-up proves even longer survival after consolidative radiation, now producing the eyebrow-raising improvement from 28 → 50(!) months. In other words, an absolute improvement in survival of almost 2 years. Rates of survival at 5 years were improved 18 → 42%. Let’s pause here to consider why this wasn’t replicated in a trial like ECOG E2108. This is where it’s worth noting that oligometastatic prostate cancer consistently appears to do especially well with local oligomet treatment. Importantly, though, a post hoc sensitivity analysis excluding prostate cancer showed a consistent, albeit smaller, improvement in survival rate at 5 years from 16 → 33%. Finally, the authors advocate for continued post-progression SABR to sites of recurrence as received by roughly one-third of long term survivors.
TBL: Recognizing the numbers here are small, particularly per disease site, great gain is likely achievable with subsequent trials investigating consolidative treatment for oligomets in the appropriate populations. | Palma, J Clin Oncol 2020