Metastatic melanoma patients who are also obese have higher survival rates than those with normal body mass indexes, according to a study published in The Lancet Oncology (Mar. 2018; 19(3):310–322). The association was primarily seen in male patients treated with targeted or immune therapy. Obesity was linked to an almost doubling in overall survival in these men—although no such association was seen in female patients, nor in those treated with chemotherapy.
“These results have implications for the design of future clinical trials for patients with metastatic melanoma and the magnitude of the benefit found supports further investigation of the underlying mechanism of these associations,” wrote the study authors, who represented institutions such as The University of Texas MD Anderson Cancer Center in Houston, the Robert H. Lurie Comprehensive Cancer Center of Northwestern University in Chicago, Melanoma Institute Australia in Wollstonecraft, Australia, and University Hospital Essen in Essen, Germany.
Researchers concluded that these findings are an example of the “obesity paradox” in melanoma—the occurrence observed in some types of cancer where obesity is linked to an increased risk of diagnosis, but also a survival advantage in some patients with established disease.
From Aug. 2, 2006 to Jan. 15, 2016, six independent clinical cohorts of 1,918 metastatic melanoma patients who had been treated with targeted therapy, immunotherapy, or chemotherapy were included in the analysis. Investigators classified patients according to body mass index (BMI), in accordance with World Health Organizations definitions, as underweight, normal, overweight, or obese. Patients without BMI and underweight patients were excluded from the retrospective study.
The primary outcomes were the associations between BMI and progression-free survival or overall survival.
A total of 36% (694) of patients had normal BMIs, 37% (711) were overweight, and 27% (513) were obese.
The beneficial effects of obesity were only observed in patients who underwent targeted therapy (HR 0·72 [0·57–0·91] for progression-free survival and 0·60 [0·45–0·79] for overall survival) and immunotherapy (HR 0·75 [0·56–1·00] and 0·64 [0·47–0·86]). No such association was seen in female patients (HR 0·85 [0·61–1·18, p interaction=0·03]), or in participants treated with chemotherapy (HR 0·87 [0·65–1·17, p interaction=0·61] for progression-free survival and 1·03 [0·80–1·34, p interaction=0·01] for overall survival).