A new Swedish case-control study recently presented at the annual American Association for Cancer Research (AACR) Meeting in Washington, D.C. has reported that girls who are overweight at age seven are less likely to eventually develop postmenopausal breast cancer than slender girls. The study was designed to investigate the associations between childhood body size and risk of postmenopausal breast cancer. The study included 2,818 breast cancer cases and 3,111 cancer-free controls. Nine categories of somatotype (measurement of body shape and size) were used to classify childhood body size.

A large body type at age seven was found to be associated with a 27% lower risk of postmenopausal breast cancer than a slender body type. This was despite the fact that overweight girls were more likely to have other factors known to increase the risk of breast cancer (such as lower age of first period, high adult body mass index (BMI) and high breast density). The protective effect of a large body type was observed within all possible combinations of estrogen receptor (ER) and progesterone receptor (PR) status. However, a stronger protective effect was found for ER- than for ER+ breast cancer. Body type at age seven was not found to be associated with size of tumor, histology, grade or lymph node status. The authors conclude that greater body size at age seven is associated with a decreased risk of postmenopausal breast cancer, and that the protective effect is stronger for the ER- breast cancer than for the ER+ breast cancer.