RADT-88. STEREOTACTIC RADIOSURGERY AND IMMUNOTHERAPY FOR BRAIN METASTASES SECONDARY TO RENAL CELL CARCINOMA

Abstract Stereotactic radiosurgery (SRS) and immunotherapy (IT) are believed to have synergistic effects in the treatment of brain metastases (BMs) that arise secondary to renal cell carcinoma (RCC). We retrospectively reviewed and evaluated patients meeting such criteria at a tertiary cancer center. The cohort consisted of 28 patients (20 male and 8 female) with 24 clear-cell carcinoma and 2 papillary carcinoma confirmed subtypes. They developed 118 BMs distributed across supratentorial (84.7%) and infratentorial (15.3%) sites. Of 116 SRS targets, 107 (92.2%) were intact tumors and 9 (7.8%) were post-resection cavities. In one case, 3 BMs were surgically removed together, and the cavity was treated as a single SRS target. Sixteen of 28 (57.1%) patients started IT before undergoing SRS (IT-exposed), 13 of 28 (46.4%) started immune checkpoint blockade (ICB) therapy before undergoing SRS (ICB-exposed), and 12 of 28 (42.9%) had not started any IT before undergoing SRS (IT-naive). Of the 16 IT-exposed patients, 11 (68.8%) had PD-1 or PD-L1 blockade (pembrolizumab, nivolumab, or atezolizumab), 5 (31.3%) had CTLA-4 blockade (ipilimumab), 3 had cytokine therapy (high-dose interleukin-2), 3 had anti-RANKL therapy (denosumab), and 1 had anti-VEGF therapy (bevacizumab) on board prior to SRS. Median follow-up after SRS was 29 (range: 3 to 97) months for the whole cohort. Median overall survival following SRS was 30, 33, and 25 months for the IT-exposed, ICB-exposed, and IT-naive groups, respectively. Ninety-nine lesions were evaluable on imaging with a median follow-up time of 11 (range: 1 to 97) months. On last imaging, the radiographic responses were regression, stable, and progression for 32, 36, and 31 lesions, respectively, demonstrating overall local control of 68.7%. Local control was 74.4%, 69.4%, and 65.0% for IT-exposed, ICB-exposed, and IT-naive lesions. Overall, IT-sensitized SRS achieves robust local control of BMs and improved survival in a large cohort of patients with RCC.