Breast cancer risk in young women and history of selected medical conditions

Background Several common medical conditions are associated with altered ho rmone levels, and may thus plausibly influence breast cancer risk. Few stud ies have examined such relationships, and we utilized a population-based ca se-control study of young women in the US to examine breast cancer risk fol lowing a history of various medical conditions. Relationships between breas t cancer and each medical condition examined are biologically plausible, an d relevant in terms of public health. Methods The study included 2173 breast cancer cases and 1990 population-bas ed controls from three areas of the US, under 55 years, who were administer ed a questionnaire including details of physician-diagnosed medical conditi ons. Results No significantly increased or decreased breast cancer risk was asso ciated with a history of thyroid disease, gallbladder disease, colorectal p olyps, diabetes, high blood pressure, high cholesterol or surgery for endom etriosis. There was some evidence of an increased breast cancer risk associ ated with ovarian cysts among women who did not receive an oophorectomy (re lative risk [RR] = 1.94, 95% CI: 1.0-3.9). Non-significant increases in bre ast cancer risk were observed following diagnoses of several other cancers, including thyroid cancer, basal cell carcinoma, Hodgkin's disease and mali gnant melanoma. Conclusions To conclude, our generally null results from this large, popula tion-based study support results from previous studies in providing reassur ance that women with a history of several common medical conditions do not appear to be at an increased risk of breast cancer at a young age.