Preclinical and early clinical data indicate that stereotactic body radiotherapy (SBRT) could work synergistically with checkpoint inhibitors and increase response rates. Given the potential synergistic effect between both treatments, the associated toxicity might also be increased. We conducted two phase I trials combining SBRT with ipilimumab (n=13) or pembrolizumab (n=18) in metastatic/inoperable melanoma and metastatic urothelial carcinoma respectively. To evaluate the effect of SBRT timing, patients were randomised to either sequential or concurrent SBRT in the latter trial. To assess early efficacy, a phase II trial of SBRT and nivolumab was conducted in metastatic/inoperable melanoma (n=20). Our data shows that SBRT combined with ipilimumab, nivolumab or pembrolizumab is safe and might increase efficacy in a subset of patients.

(BELG J MED ONCOL 2020;14(1):28–30)