Comparative Case‐referent Study of Risk Factors among Hormone‐related Female Cancers in Japan

To assess the impact of reproductive and anthropometric factors as a risk indicator for female cancers in hormone‐related organs, i.e., the breast, endometrium and ovary, we conducted a comparative case‐referent study using data from the Hospital‐based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan. The case group consisted of 1,465, 133 and 99 women who had first been diagnosed as having breast, endometrial and ovarian cancer, respectively. The referents were 25,488 female first‐visit outpatients who had not previously been diagnosed with any type of cancer. The odds ratios (ORs) and their 95% confidence intervals (95%CI) were estimated using an unconditional logistic regression model. An inverse association with experience of delivery and a positive association with body mass index (BMI) and with change of BMI after 20 years of age, were observed consistently for all three cancer sites. We observed similar risk and protective factors for breast and endometrial cancer, but the effect of reproduction and overweight condition (BMI≥25) were more prominent in endometrial cancer. Although the present study failed to find site‐specific risk factors for ovarian cancer, the results provided evidence that being overweight and/or weight gain in adult life is a common risk factor for all three cancer sites. The results obtained from this study suggested that avoidance of weight gain may reduce the risk of female hormone‐related cancers.