SELECTED MEDICAL CONDITIONS AND RISK OF BREAST-CANCER

Several diseases are known or suspected to be associated with altered levels of hormones and growth factors that may influence breast cancer risk. To elucidate this possibility, we studied the relationship betw een 23 medical conditions or procedures and breast cancer risk by mean s of data from a multicentric case-control study conducted between 199 1 and 1994 in six Italian areas. The study included 2569 histologicall y confirmed incident cases of breast cancer (median age 55 years, rang e 23-74 years) and 2588 control women (median age 56 years, range 20-7 4 years) admitted to the same hospitals as cases for a variety of acut e conditions unrelated to known or suspected risk factors for breast c ancer. After allowance for education, parity and body mass index, elev ated odds ratios (ORs) emerged for history of diabetes mellitus in pos t-menopausal women (OR = 1.5, 95% CI 1.1-2.0), hypertension in pregnan cy (OR = 1.8, 95% CI 1.0-3.4) and breast nodules (OR = 1.3, 95% CI 1.0 -1.7). Risk decreases were associated with ovarian ablation for ovaria n cysts (OR = 0.5, 95% CI 0.3-0.7) and with thyroid nodules (OR = 0.7, 95% CI 0.5-0.9) but not with the combination of any type of benign th yroid disease. While most examined conditions seemed unrelated to brea st cancer risk, the association with late-onset diabetes is of special interest as it suggests a role of hyperinsulinaemia and insulin resis tance in breast cancer promotion. It also points to preventive lifesty le modifications.