Conflicts of Interest Statement D.L. reports funding by a postdoctoral fellowship from the Society for Immunotherapy of Cancers which is funded in part by an educational grant from Bristol-Meyers Squibb (BMS). BMS has had no input into the conception, conduct, or reporting of the submitted work. D.C. has received consulting (GSK, Lilly, Boston Pharmaceuticals) and travel/speaking (Merck) support, outside the scope of the present work. G.M.B. had sponsored research agreements with Takeda Oncology, Palleon Pharmaceuticals, Olink Proteomics, which were not used to support this work. She served as a speaker for Novartis and on scientific advisory boards for Nektar Therapeutics and Novartis and consults for Merck, all of which are outside the scope of this work. P.K.B has consulted

Melanoma-derived brain metastases (MBM) represent an unmet clinical need because central nervous system (CNS) progression is frequently an end-stage of the disease. Immune checkpoint inhibitors (ICI) provide a clinical opportunity against MBM; however, the MBM tumor microenvironment (TME) has not been fully elucidated in the context of ICI. To dissect unique elements of the MBM TME and correlates of MBM response to ICI, we collected 32 fresh MBM and performed single-cell RNA sequencing of the MBM TME and T-cell receptor clonotyping on T cells from MBM and matched blood and extracranial lesions. We observed myeloid phenotypic heterogeneity in the MBM TME, most notably multiple distinct neutrophil states, including an IL8-expressing population that correlated with malignant cell epithelial-to-mesenchymal transition. Additionally, we observed significant relationships between intracranial T-cell phenotypes and the distribution of T-cell clonotypes intracranially and peripherally. We found that the phenotype, clonotype, and overall number of MBM-infiltrating T cells were associated with response to ICI, suggesting that ICI-responsive MBMs interact with peripheral blood in a manner similar to extracranial lesions. These data identify unique features of the MBM TME that may represent potential targets to improve clinical outcomes for patients with MBM.

Background Immune checkpoint blockade has systemic efficacy in patients with metastatic melanoma, including those with brain metastases (MBMs). However, immunotherapy‐induced intracranial tumoral inflammation can lead to neurologic compromise, requiring steroids, which abrogate the systemic efficacy of this approach. We investigated whether upfront neurosurgical resection of MBM is associated with a therapeutic advantage when performed prior to initiation of immunotherapy. Material and Methods An institutional review board‐approved, retrospective study identified 142 patients with MBM treated with immune checkpoint blockade between 2010 and 2016 at Massachusetts General Hospital, of whom 79 received surgery. Patients were classified based on the temporal relationship between immunotherapy, surgery, and development of central nervous system metastases. Overall survival (OS) was calculated from the date of diagnosis of MBM until death from any cause. Multivariate model building included a prognostic Cox model of OS, the effect of immunotherapy and surgical sequencing on OS, and the effect of immunotherapy and radiation sequencing on OS. Results The 2‐year overall survival for patients treated with cytotoxic T‐lymphocyte antigen 4, programmed death 1, or combinatorial blockade was 19%, 54%, and 57%, respectively. Among immunotherapy‐naïve melanoma brain metastases, surgery followed by immunotherapy had a median survival of 22.7 months (95% confidence interval [CI], 12.6–39.2) compared with 10.8 months for patients treated with immunotherapy alone (95% CI, 7.8–16.3) and 9.4 months for patients treated with immunotherapy followed by surgery (95% CI, 4.1 to ∞; p = .12). On multivariate analysis, immunotherapy‐naïve brain metastases treated with immunotherapy alone were associated with increased risk of death (hazard ratio, 1.72; 95% CI, 1.00–2.99) compared with immunotherapy‐naïve brain metastases treated with surgery followed by immunotherapy. Conclusion In treatment‐naïve patients, early surgical resection for local control should be considered prior to commencing immunotherapy. A prospective, randomized trial comparing the sequence of surgery and immunotherapy for treatment‐naïve melanoma brain metastases is warranted. Implications for Practice In this retrospective study of 142 patients with melanoma brain metastases treated with immune checkpoint blockade, the development of melanoma brain metastases following immunotherapy was associated with decreased survival compared with diagnosis of immunotherapy‐naïve brain metastases. The benefit of surgical intervention was seen in immunotherapy‐naïve brain metastases in contrast to brain metastases that developed on immunotherapy. These results suggest that upfront local control with surgery for immunotherapy‐naïve melanoma brain metastasis may provide a bridge toward immunotherapy‐mediated systemic control.