(S050) Stereotactic Radiosurgery in the Setting of Immune Checkpoint Blockade Results in Improved Intracranial Control Compared With Whole-Brain Irradiation for Greater Than Three Melanoma Brain Metastases

Penny Fang, MD, Wen Jiang, MD, Betty Y. Kim, MD, PhD, Isabella C. Glitza, MD, PhD, Anita Mahajan, MD, Michael A. Davies, MD, PhD, Franco DeMonte, MD, Patrick Hwu, MD, Erik P. Sulman, MD, PhD, Paul D. Brown, MD, Jing Li, MD, PhD; UT MD Anderson Cancer Center; Mayo Clinic Jacksonville

BACKGROUND: Whole-brain radiation therapy (WBRT) is a commonly accepted treatment of choice for patients with ≥ 3 brain metastases, because of concern about intracranial microscopic disease. With increased use of immune checkpoint inhibitors in metastatic cancers, several studies have suggested that improved intracranial control by stereotactic radiosurgery (SRS) is also achievable. We investigated whether SRS, combined with cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4) blockade, can result in superior intracranial control compared with WBRT alone in patients with ≥ 3 melanoma brain metastases.

METHODS: From 2007 to 2014, patients diagnosed with metastatic melanoma who received ipilimumab (Ipi) and SRS for new brain metastases after the initiation of immunotherapy were identified. Only patients treated with ≥ 3 lesions were included. A matching cohort of patients who received WBRT without prior immunotherapies was identified and compared.

RESULTS: A total of 59 patients with metastatic melanoma were included in the study; 22 were treated with SRS + Ipi and 37 with WBRT alone. Patients received at least two doses prior to SRS. The majority of the patients (86.4%) received SRS within 5 months from the last Ipi treatment. The median number of treated brain metastases was 6 for SRS + Ipi (range: 4–22) and 7 (range: 4–25) for WBRT. Patients treated with SRS + Ipi had significantly improved intracranial control compared with WBRT alone, with a 12-month intracranial progression-free rate of 26% vs 13% (P = .028). There was a trend toward improved overall survival (OS) for patients who received SRS + Ipi (median: 9.61 mo vs 4.47 mo; P = .09). The improved intracranial control for SRS + Ipi remained significant on multivariate analysis.

CONCLUSIONS: SRS, in the setting of systemic immunotherapy, may provide improved intracranial control compared with WBRT in patients with ≥ 3 melanoma brain metastases. Future prospective studies may expand the utility of SRS and spare selective patients with large intracranial disease burdens from toxicities associated with WBRT.

Proceedings of the 98^th Annual Meeting of the American Radium Society -americanradiumsociety.org