Do these treatments clash?

Top Line: How safe is multi-site stereotactic body radiotherapy (SBRT) prior to immunotherapy?
The Study: Aggressive local treatment of oligomets in certainly in vogue, but so is immunotherapy. This single arm phase I study reported in JCO explored the safety of performing SBRT to multiple metastatic sites (excluding brain) immediately prior to switching from a failed chemo regimen to pembrolizumab. This was a basket study and included a wide variety of primary malignancies that were heavily pre-treated with a median of five previously-failed regimens. SBRT was delivered in anywhere from 50 Gy / 5, 45 Gy / 3, or 30 Gy / 3 depending on location, and pembro started 7 days after completion of radiation. Major (at least grade 3) toxicities included pneumonitis, colitis, or hepatic toxicity in about 6 of 79 of patients. Of note, both toxicity and response rates were similar to historic rates with pembro alone.
Bottom Line: Pembro after multi-site SBRT was well tolerated with a dose-limiting toxicity rate of <10% (mostly at irradiated sites), but we need more data establishing if SBRT enhances the efficacy of immunotherapy before this combo is ready for the runway.


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