Physical activity and breast cancer risk by pathological subtype.

OBJECTIVE: To examine the influence of physical activity on breast cancer risk and evaluate whether adherence to international recommendations is associated with a decreased risk. METHODS: This is a multicenter matched case-control study where 698 pairs completed a physical activity questionnaire. Recreational physical activity during the last year was quantified in metabolic equivalent hours per week (MET-h/week) and categorized in activities of moderate (3.0-5.9 MET) and vigorous (>6 MET) intensity. The adherence to World Cancer Research Fund and the American Institute for Cancer Research recommendation was also assessed. The association with breast cancer risk, overall and by pathologic subtype, was evaluated using conditional and multinomial logistic regression models. RESULTS: Mean MET-h/week was 16.6 among cases and 20.4 among controls. Premenopausal breast cancer risk decreased by 5% (P=0.007) for every 6 MET-h/week increase in energy expenditure. By contrast, postmenopausal women needed to do more intense exercise to observe benefits. The protection was more pronounced for nulliparous women, as well as for hormone receptor positive and HER2+ tumors. Physically inactive women displayed a 71% increased risk when compared with those who met the international recommendation (P=0.001). Finally, women who were inactive during the previous year, regardless of the overall physical activity reported in previous periods, showed an increased risk when compared to always active women. CONCLUSIONS: Women who report adherence to international physical activity recommendations entail a significant decrease in risk for all pathologic breast cancer subtypes. This is of particular interest in Spain, where a significant increase in overweight and obesity in recent decades is observed.

Overeating, caloric restriction and breast cancer risk by pathologic subtype: the EPIGEICAM study.

This study analyzes the association of excessive energy intake and caloric restriction with breast cancer (BC) risk taking into account the individual energy needs of Spanish women. We conducted a multicenter matched case-control study where 973 pairs completed lifestyle and food frequency questionnaires. Expected caloric intake was predicted from a linear regression model in controls, including calories consumed as dependent variable, basal metabolic rate as an offset and physical activity as explanatory. Overeating and caloric restriction were defined taking into account the 99% confidence interval of the predicted value. The association with BC risk, overall and by pathologic subtype, was evaluated using conditional and multinomial logistic regression models. While premenopausal women that consumed few calories (>20% below predicted) had lower BC risk (OR = 0.36; 95% CI = 0.21-0.63), postmenopausal women with an excessive intake (≥40% above predicted) showed an increased risk (OR = 2.81; 95% CI = 1.65-4.79). For every 20% increase in relative (observed/predicted) caloric intake the risk of hormone receptor positive (p-trend < 0.001) and HER2+ (p-trend = 0.015) tumours increased 13%, being this figure 7% for triple negative tumours. While high energy intake increases BC risk, caloric restriction could be protective. Moderate caloric restriction, in combination with regular physical activity, could be a good strategy for BC prevention.