Obesity is Associated with Longer Survival Independent of Sarcopenia and Myosteatosis in Metastatic and/or Castrate-Resistant Prostate Cancer.

Abstract

Obesity (body mass index 30 kg/m2 or greater) is associated with better overall survival in metastatic prostate cancer. Conversely, low muscle mass (sarcopenia) and low muscle radiodensity (myosteatosis) are associated with worse overall survival in many cancers. This study seeks to evaluate the relationship of sarcopenia, myosteatosis and obesity with overall survival in men with metastatic or castrate-resistant prostate cancer. Retrospective analysis of men with metastatic or castrate-resistant prostate cancer and computerized tomography of abdomen/pelvis presenting to the Vanderbilt Comprehensive Prostate Cancer Clinic from 2012 to 2017 was performed. Demographic, pathological and survival data were described, with sarcopenia and myosteatosis determined from abdominal skeletal muscle area and skeletal muscle radiodensity, respectively. Kaplan-Meier curves and log-rank tests estimated the effect of body composition on survival. Multivariable Cox proportional hazard models were performed adjusting for age, Charlson comorbidity index, race and clinical stage. ANOVA was used to compare obese and nonobese men with and without sarcopenia or myosteatosis. Of 182 men accrued, 37.4% were obese, 53.3% sarcopenic and 59.3% myosteatotic. Over a median followup of 33.9 months, body mass index was associated with reduced mortality (HR 0.93, p=0.02), as was visceral adiposity (HR 0.99, p=0.003). Men with high body mass index without sarcopenia/myosteatosis lived significantly longer than men with high body mass index with sarcopenia/myosteatosis or normal body mass index men (F[3,91]=4.03, p=0.01). Both high body mass index and visceral adiposity in metastatic or castrate-resistant prostate cancer are associated with reduced mortality, independent of sarcopenia and myosteatosis. Therefore, routine clinical workup should include calculation of body mass index and measurement of waist circumference. Morphometric analysis of computerized tomography imaging can identify patients at risk for poor prognosis.