Obese men have higher melanoma survival

Obesity almost doubles the odds of survival in men with metastatic melanoma – provided they are not treated with chemotherapy (Lancet Oncology 2018; DOI: https://doi.org/10.1016/S1470-2045(18)30078-0).

The surprise finding comes from an analysis of six randomised trials published between 2006 and 2015 involving a total of 1918 men and women treated with targeted therapies (dabrafenib plus trametinib and vemurafenib plus cobimetinib), immunotherapy (ipilimumab plus dacarbazine, and pembrolizumab, nivolumab, or atezolizumab) and chemotherapy with dacarbazine alone.

Compared with people with body mass index (BMI) in the normal range, those who were obese had significantly better progression-free survival (average adjusted hazard ratio [HR] 0·77; CI95% 0·66–0·90] and overall survival (HR 0·74, CI95% 0·58–0·95). The difference in survival was significant only for patients who received targeted therapy and immunotherapy; survival was increased but not significantly so with dacarbazine. Further, the benefit of targeted therapy and immunotherapy was statistically significant for men (HR 0·53, CI95% 0·40–0·70) but not women (HR 0·85, CI95% 0·61–1·18).

Obesity is generally associated with worse outcomes for cancer, though lesser increases in BMI have been associated with better outcomes than in people with normal or low BMI. The authors propose a possible mechanism for their finding: they note that the susceptibility of melanoma cells to immunotherapy is increased when a specific oestrogen receptor is activated and point out that obese men may have enhanced oestrogen synthesis due to increased aromatase expression by adipose cells.

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