Obesity and cancer: new evidence continuous update project

Introduction/Objecti ve:Obesity has been increasing sharply in Latin America in the last 20 years with some Latin American countries having the highest rates worldwide. Concurrently, breast cancer, the most common cancer among women in Latin American, has been increasing steadily. Changes in reproductive patterns, nutritional transition and other life style factors are likely to play an important role in this increase. Most studies evaluating the impact of obesity on breast cancer have been conducted in non-Hispanic whites in the US or Europe. Given the known ethnic/racial differences in hormone receptor subtype distribution, prevalence of obesity, and risk factor profiles, it is important to evaluate the role of overweight and obesity on the risk of breast cancer according to specific subtypes. Development: There are limited data on the association between obesity and breast cancer in Latin American women (2 studies) and neither study had information on receptor status. Among premenopausal women body mass index (BMI) and measures of central obesity (waist circumference and waist-to-hip ratio) were associated with a decreased risk of breast cancer, while in postmenopausal women there was no clear association of anthropometric measures (waist circumference and waist-to-hip ratio) with an increased risk of breast cancer. However, when considering the trajectory of body size over the life span (8 years to current) women with larger increase of body size were at higher risk of breast cancer in both pre and postmenopausal women compared to women who remained slim. These results support the importance of considering the evolution of body shape throughout life instead of examining body shape at specific ages when studying the association between obesity and breast cancer. Only one study evaluates the impact of obesity in breast cancer patients. Results suggest that obesity is related to poor survival. One small study from Barbados in women with African ancestry reports a decrease risk of breast cancer in premenopausal women and a non-significant inverse association in postmenopausal women. A multicenter population-based case control study, including incident breast cancer cases and matched control, is being conducted among premenopausal women in 4 Latin American countries (Chile, Colombia, Costa Rica and Mexico). Standardized evaluation of tumor phenotypes and epidemiological data will be presented .Conclusion: The limited data point toward the need for more study in the Latin American region. Most countries are undergoing a nutritional and epidemiological transition and offer the opportunity to evaluate the role of obesity and rapid weight gain on breast cancer. These studies should account for tumor phenotype and consider genetic ancestry in the evaluation as well as considering direct measures of obesity and the use of biomarkers to disentangle the complex association between obesity and breast cancer development and progression. Key words Obesity, breast cancer, women, Latin America.