Outcomes of Stereotactic Radiosurgery and Immunotherapy in Renal Cell Carcinoma Patients with Brain Metastases

Objective: The impact of immunotherapy and stereotactic radiosurgery (SRS) in treatment of brain metastases (BM) from renal cell carcinoma (RCC) has not been well investigated. Materials and Methods: Forty-eight patients with 372 RCC BM were treated with SRS and divided into those ever treated with immunotherapy versus those who never received immunotherapy. Survival and local control (LC) outcomes were studied. χ²and Mann-Whitney U tests compared categorical and continuous variables, respectively. Kaplan-Meier curves were used to estimate survival and log-rank test was used to compare survival between groups. Results: Immunotherapy and nonimmunotherapy groups contained 29 and 19 patients, respectively. Median follow-up was 23.1 months (range, 6 to 93.8 mo). Demographic and treatment variables were similar except median prescribed margin dose was significantly lower in immunotherapy group (20 vs. 22 Gy, P<0.0001). Median overall survival (OS) was 27.2 months (immunotherapy) and 14.9 months (nonimmunotherapy), P=0.14. Furthermore, patients treated with immune checkpoint inhibitor (ICI) had even better median OS compared with those who never received ICI (33 vs. 16.7 mo, P=0.03). Factors associated with improved LC were use of ICI (P=0.002) and lesion size <1000 mm³(P=0.046). There was no difference in incidence of radiation necrosis between the 2 groups (P=0.67). Conclusions: Patients with RCC BM undergoing SRS can experience prolonged survival when treated with ICI. Equally effective LC of BM was achieved when treated with immunotherapy using a 2 Gy decrease in SRS dose without increasing the risk of central nervous system toxicity.