Impact of overweight and obesity on postmenopausal breast cancer: analysis of 20-year data from Switzerland

Purpose: Greater body fatness has been identified as a risk factor for postmenopausal breast cancer. For countries with low overweight/obesity rates, data on prevalence and time course of overweight/obesity in women with breast cancer in comparison to women in the general population is limited. The Swiss female population is distinctive for two reasons: (a) low rates of overweight/obesity compared with other western countries, and (b) no obesity epidemic, i.e. stable rates of overweight/obesity for more than 10years. Methods: Overweight and obesity were analyzed in 51 to 80-year-old breast cancer patients initially diagnosed between 1990 and 2009. Patient data was derived from the Basel Breast Cancer Database (BBCD). This data was compared with the data of women of the same age from the four Swiss Health Surveys (SHS) conducted between 1992 and 2007. Differences between measured (BBCD) and self-reported (SHS) data were corrected using equations approved for the Swiss population. Results: Of 958 postmenopausal BBCD patients, 32% were overweight and 20% were obese. Of the 14,476 women of the SHS, 38% were overweight and 17% were obese. In the BBCD, there was no change in the prevalence of overweight/obesity over the last 20years. The four SHS show a convex curvature for obesity, i.e. a transient increase. No significant differences were observed between BBCD and corrected SHS data for overweight and obesity during this period. Conclusions: In this Swiss study group with a comparably low prevalence of overweight and obesity, no association between body fatness and postmenopausal breast cancer was observed