Obesity is associated with an increased risk of several cancers, such as breast or colorectal cancers. However, the relationship between obesity and prostate cancer (PCa) remains controversial. Indeed, inconsistent results have been reported between body mass index (BMI) and PCa risk, while some associations have been reported with other anthropometric indicators, such as waist circumference (WC) or waist-hip ratio (WHR), which would better illustrate the concept of body fat distribution. Therefore, we assessed a possible association between anthropometric indicators and PCa risk based on data from the EPICAP study.

EPICAP in a French population-based case-control study that enrolled 819 incident cases of PCa diagnosed in 2012 and 2013, aged less than 75 years old and residing in the department of Hérault, France. Controls were 879 age-matched (±5 y) individuals living in the same geographic area. Face-to-face interviews, using a standardized computerized questionnaire, gathered information about sociodemographic characteristics, personal medical history, lifestyle factors, physical activity, residential and occupational history. Anthropometric indicators have also been collected through the questionnaire (self-report of height at 18 years old and weight every decades) or anthropometric measures at time of interview (height, weight, waist and hip circumferences). Logistic regression models were used to assess odds ratios (ORs) for the associations between anthropometric indicators (BMI, WC and WHR) and PCa risk. Analyses were systematically adjusted for age (5-year period), family history of prostate cancer in first-degree relatives and race (Caucasians, others). Analyses were also adjusted for other potential confounding factors such as educational level or physical activity. Separate analyses were conducted by prostate cancer aggressiveness according to the Gleason score (low or intermediate score≤7 [including 3+4], high score≥7 [including 4+3]). Seeking for relevant interaction between BMI and WC or WHR, we performed stratified analyses according to BMI overweight cut-point (25kg/m²) defined by the World Health Organization.

Overall, 47.8% of men were overweight and 23.4% were obese, similarly distributed between cases and controls (OR 0.98, 95% CI 0.78–1.23, OR 0.91 95% CI 0.67–1.23, respectively). We observed a slight, but not significant increased risk of PCa for men with a WC above 94cm (OR 1.20, 95% CI 0.95–1.51) and an increased risk of PCa for men with a WHR greater or equal to 0.95 (OR 1.27, 95% CI 1.01–1.60), with more pronounced associations after adjustment for BMI (OR 1.48, 95% CI 1.11–1.97, OR 1.39, 95% CI 1.09–1.79, respectively). In addition, analyses stratified on BMI showed that men with a BMI<25km/m² had a higher risk of PCa, either for WC>94cm or WHR≥0.95 (OR 1.63, 95% CI 1.05–2.52, OR 1.76, 95% CI 1.18–2.63, respectively). Nevertheless, interactions were not significant for WC (P=0.23) and close to significance for WHR (P=0.07). Associations regarding central obesity indicators, adjusted for BMI, were more pronounced in men with aggressive prostate cancer, either for WC>94cm (OR 2.30, 95% CI 1.38–3.83) or WHR≥0.95 (OR 1.51, 95% CI 0.98–2.32).

Our results suggest that BMI itself is not associated with prostate cancer, while central obesity is associated with an increased risk of prostate cancer, especially aggressive prostate cancer.