Reproductive characteristics and risk of kidney cancer: Iowa Women's Health Study

ObjectivesKidney (renal cell) cancer accounts for approximately 3–4% of all new cases of primary cancer diagnosed in the United States. A relationship between kidney cancer and female reproductive factors has been hypothesized but supporting evidence is inconsistent. Our objectives were to explore the relationship between female reproductive factors and kidney cancer and identify independent risk factors related to female reproductive history and its effects on development of kidney cancer.MethodsWe measured risk factors for kidney cancer and reproductive characteristics in a group of 37,440 postmenopausal women in Iowa. From 1986 to 2003, 165 cases of incident kidney cancer were identified through a statewide cancer registry.ResultsAfter adjustment for age and other risk factors, past use of estrogen showed an increased risk of renal cancer (RR 1.56; 95% CI 1.13–2.17) when compared to no use. Women with no live birth (RR 1.91, p = 0.02) and women with three to four live births (RR 1.62, p = 0.02) also had an increased risk of kidney cancer when compared with women who had one to two live births. There was also a lower risk of kidney cancer with greater lifetime duration of ovulation.ConclusionAlthough most reproductive variables were not significantly associated with kidney cancer, our study indicates that a greater exposure to estrogens may increase risk for kidney cancer.