Toxicity and outcomes of melanoma brain metastases treated with stereotactic radiosurgery: the risk of subsequent symptomatic intralesional hemorrhage exceeds that of radiation necrosis.

purposeWe aimed to assess the outcomes and patterns of toxicity in patients with melanoma brain metastases (MBM) treated with stereotactic radiosurgery (SRS) with or without immunotherapy (IO).

methodsFrom a prospective registry, we reviewed MBM patients treated with single fraction Gamma Knife SRS between 2008 and 2021 at our center. We recorded all systemic therapies (chemotherapy, targeted therapy, or immunotherapy) administered before, during, or after SRS. Patients with prior brain surgery were excluded. We captured adverse events following SRS, including intralesional hemorrhage (IH), radiation necrosis (RN) and local failure (LF), as well as extracranial disease status. Distant brain failure (DBF), extracranial progression-free survival (PFS) and overall survival (OS) were determined using a cumulative Incidence function and the Kaplan-Meier method.

resultsOur analysis included 165 patients with 570 SRS-treated MBM. Median OS for patients who received IO was 1.41 years versus 0.79 years in patients who did not (p = 0.04). Ipilimumab monotherapy was the most frequent IO regimen (30%). In the absence of IO, the cumulative incidence of symptomatic (grade 2 +) RN was 3% at 24 months and remained unchanged with respect to the type or timing of IO. The incidence of post-SRS g2 + IH in patients who did not receive systemic therapy was 19% at 1- and 2 years compared to 7% at 1- and 2 years among patients who did (HR: 0.33, 95% CI 0.11-0.98; p = 0.046). Overall, neither timing nor type of IO correlated to rates of DBF, OS, or LF. Among patients treated with IO, the median time to extracranial PFS was 5.4 months (95% IC 3.2 - 9.1).

conclusionThe risk of g2 + IH exceeds that of g2 + RN in MBM patients undergoing SRS, with or without IO. IH should be considered a critical adverse event following MBM treatments.