Treatment of brain metastases with stereotactic radiosurgery and immune checkpoint inhibitors: An international meta-analysis of individual patient data

Background and purpose While the combination of stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICI) is becoming more widely used in the treatment of brain metastases (BM), there is a paucity of prospective data to validate both the safety and efficacy, as well as the optimal timing of these two therapies relative to one another. Methods A PICOS/PRISMA/MOOSE selection protocol was used to identify 17 studies across 15 institutions in 3 countries. Inclusion criteria were patients: diagnosed with BM; treated with SRS/ICI, either concurrently or non-concurrently; with at least one of the primary or secondary outcome measures reported. Weighted random effects meta-analyses using the DerSimonian and Laird method were performed. The primary outcome was 1-year overall survival (OS). Secondary outcomes were 1-year local control (LC), 1-year regional brain control (RBC), and radionecrosis incidence. Results A total of 534 patients with 1,570 BM were included. The 1-year OS was 64.6% and 51.6% for concurrent and non-concurrent therapy, respectively (p < 0.001). Local control at 1-year was 89.2% and 67.8% for concurrent and non-concurrent therapy, respectively (p = 0.09). The RBC at 1-year was 38.1% and 12.3% for concurrent and ICI administration prior to SRS, respectively (p = 0.049). The overall incidence of radionecrosis for all studies was 5.3%. Conclusions Concurrent administration of SRS/ICI may be associated with improved safety and efficacy versus sequential therapy. These findings, however, are hypothesis-generating and require further validation by ongoing and planned prospective trials.