After closure of the SABR-COMET trial, the British Columbia Cancer Agency continued offering oligometastatic SBRT, but only on the prospective, single arm SABR-5 trial. The primary focus of the trial was toxicity–meaning this is an excellent study of real-world toxicity from oligometastatic SBRT. Eligible patients had a treated or controlled primary and up to 5 oligometastases amenable to SBRT. PTV coverage was secondary to OAR constraints with the caveat that if 100% of the PTV received <50% of the prescribed dose, the patient should not be treated with SBRT. Dose and fractionation by site and OAR constraints are outlined in the protocol. Among a whopping 399 patients (SABR-COMET had 99), >90% were treated for 1-2 oligometastases with prostate cancer being the most common histology. Sites included the lung (33%), non-spine bone (28%), spine (14%), nodes (13%), liver (5%), and adrenal (3%). Overall toxicity was low with a 5.1% rate of grade 3+ toxicity including 0.5% grade 4 and no grade 5 toxicity. So, if you’re looking for an aggressive, but safe model for oligometastatic SBRT until we have phase 3 data, look no further than SABR-5. | Olson, ASTRO 2021


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