Breast cancer risk in women with a primary ovarian cancer - a case-controlstudy

Register-based studies show that women with ovarian cancer are at increased risk of developing breast cancer. Primary suggested explanations are hered ity factors and a common hormonal aetiology. However, clinical surveillance that is provided for cancer patients during, and after, treatment of their primary malignancies together with possible mistakes in the registering pr ocedures could affect the risk estimates. In order to examine these factors in women registered with ovarian cancer who develop subsequent breast canc er, a case-control Study was performed. Using a regional Swedish cancer reg istry including 5060 women registered with ovarian cancer, 89 cases of brea st cancer were found. After corrections for discrepancies in the registered and recorded information, 75 cases remained, of which 72 cases were includ ed in the study. Information concerning possible risk factors were extracte d from hospital records and compared with 177 matched controls. Suggested r isk factors such as parity (relative risk (RR) = 1.41), late age at menopau se (52-61 years: RR 1.61) and heredity for breast and/or ovarian cancer (RR = 1.50) were all connected with a nonsignificant increased risk of subsequ ent breast cancer. In all, 43% of the breast cancer cases were revealed wit hout preceding symptoms at clinical follow-up, indicating that increased cl inical surveillance is a factor of importance when explaining the increased risk. The fact that only 75 (missing records included) out of the 89 regis tered breast cancer cases could be linked to the preceding ovarian cancer i ndicates that the actual risk of developing breast cancer is smaller than p reviously described. The clinical implications from these findings could be that, beside general screening programmes and health controls offered to w omen in cancer-prone families, additional mammography examinations based on the assumption of an increased risk of breast cancer are not warranted in ovarian cancer patients. (C) 2001 Elsevier Science Ltd. All rights reserved .