Weight change and risk of endometrial cancer.

BACKGROUND Obesity is an established risk factor for endometrial cancer. Less well understood is the role of weight gain and weight change in determining risk. METHODS We analysed data from a population-based case-control study to evaluate the associations of body mass index (BMI), weight gain, and weight cycling with risk of endometrial cancer. Cases (n=740) under age 80 with a new diagnosis of endometrial cancer were identified from Wisconsin's cancer registry. Controls (n=2342) were randomly selected from driver's license lists and Medicare beneficiary files. Body size at three time points and other risk factor information were ascertained by interview in 1992-95. RESULTS Endometrial cases were more likely than controls to be nulliparous, have early ages at menarche and late ages at menopause, be diabetic, smoke cigarettes, and use post-menopausal hormones. After adjustment for these factors, increasing BMI was associated with increased risk (P-trend<0.001); women in the top quartile of BMI (>29 kg/m2) had a 3-fold greater risk of endometrial cancer [95% confidence interval (95% CI) 2.4-4.2] compared with women in the lowest quartile (<23 kg/-m2). For each 5 kg weight gain, the odds ratio (OR) for endometrial cancer risk equalled 1.2 (95% CI 1.2-1.3). History of weight cycling modestly increased risk after adjustment for BMI and other factors (OR=1.3; 95% CI 1.0-1.6). In addition, women who reported sustained weight loss had a reduced risk of endometrial cancer (OR=0.7; 95% CI 0.6-0.9). CONCLUSIONS These results suggest that weight gain and lack of weight stability are associated with risk of endometrial cancer.