Background Obesity has been linked to increased mortality in several cancer types; however, the relationship between obesity and survival in metastatic melanoma is unknown. The aim of this study was to examine the association between BMI, progression-free survival (PFS), and overall survival (OS) in metastatic melanoma. Methods This study included 6 independent cohorts for a total of 1918 metastatic melanoma patients. These included two targeted therapy cohorts [randomized control trials (RCTs) of dabrafenib and trametinib (n=599) and vemurafenib and cobimetinib (n=240)], two immunotherapy cohorts [RCT of ipilimumab + dacarbazine (DTIC) (n=207) and a retrospective cohort treated with anti-PD-1/PDL-1 (n=331)], and two chemotherapy cohorts [RCT DTIC cohorts (n=320 and n=221)]. BMI was classified as normal (BMI 18 to <25; n=694 of 1918, 36.1%) overweight (BMI 25-29.9; n=711, 37.1%) or obese (BMI≥30; n=513, 26.7%). The primary outcomes were the association between BMI, PFS, and OS, stratified by treatment type and sex. These exploratory analyses were based on previously reported intention-to-treat data from the RCTs. The effect of BMI on PFS and OS was assessed by multivariable-adjusted Cox models in independent cohorts. In order to provide a more precise estimate of the association between BMI and outcomes, as well as the interaction between BMI, sex, and therapy type, adjusted hazard ratios were combined in mixed-effects meta-analyses and heterogeneity was explored with meta-regression analyses. Findings In the pooled analysis, obesity, as compared to normal BMI, was associated with improved survival in patients with metastatic melanoma [average adjusted hazard ratio (HR) and 95% CI: 0.77 (0.66-0.90) and 0.74 (0.58-0.95) for PFS and OS, respectively]. The survival benefit associated with obesity was restricted to patients treated with targeted therapy [0.72 (0.57-0.91) and 0.60 (0.45-0.79) for PFS and OS, respectively] and immunotherapy [0.75 (0.56-1.00) and 0.64 (0.47-0.86)]. No associations were observed with chemotherapy [0.87 (0.65-1.17) and 1.03 (0.80-1.34); treatment p for interaction = 0.61 and 0.01, for PFS and OS, respectively]. The prognostic effect of BMI with targeted and immune therapies differed by sex with pronounced inverse associations in males [PFS 0.67 (0.53-0.84) and OS 0.53 (0.40-0.70)], but not females [PFS 0.92 (0.70-1.23) and OS 0.85 (0.61-1.18), sex p for interaction= 0.08 and 0.03, for PFS and OS, respectively] Interpretation Obesity is associated with improved PFS and OS in metastatic melanoma, driven by strong associations observed in males treated with targeted or immune therapy. The magnitude of the benefit detected supports the need for investigation into the underlying mechanism of these unexpected observations Funding ASCO/CCF Young Investigator Award and ASCO/CCF Career Development Award to JLM

We have shown that the aged microenvironment increases melanoma metastasis, and decreases response to targeted therapy, and here we queried response to anti-PD1. We analyzed the relationship between age, response to anti-PD1, and prior therapy in 538 patients. We used mouse models of melanoma, to analyze the intratumoral immune microenvironment in young versus aged mice and confirmed our findings in human melanoma biopsies. Patients over the age of 60 responded more efficiently to anti-PD-1, and likelihood of response to anti-PD-1 increased with age, even when we controlled for prior MAPKi therapy. Placing genetically identical tumors in aged mice (52 weeks) significantly increased their response to anti-PD1 as compared with the same tumors in young mice (8 weeks). These data suggest that this increased response in aged patients occurs even in the absence of a more complex mutational landscape. Next, we found that young mice had a significantly higher population of regulatory T cells (Tregs), skewing the CD8:Treg ratio. FOXP3 staining of human melanoma biopsies revealed similar increases in Tregs in young patients. Depletion of Tregs using anti-CD25 increased the response to anti-PD1 in young mice. While there are obvious limitations to our study, including our inability to conduct a meta-analysis due to a lack of available data, and our inability to control for mutational burden, there is a remarkable consistency in these data from over 500 patients across 8 different institutes worldwide. These results stress the importance of considering age as a factor for immunotherapy response. .

Cancer immunotherapy utilizing blockade of the PD-1/PD-L1 checkpoint has revolutionized the treatment of a wide variety of malignancies, leading to durable therapeutic responses not typically seen with traditional cytotoxic anticancer agents. However, these therapies are ineffective in a significant percentage of patients, and some initial responders eventually develop resistance to these therapies with relapsed disease. The mechanisms leading to both primary and acquired resistance to PD-1/PD-L1 inhibition are varied and can be both multifactorial and overlapping in an individual patient. As the mechanisms of resistance to PD-1/PD-L1 blockade continue to be further characterized, new strategies are being developed to prevent or reverse resistance to therapy, leading to improved patient outcomes.

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