Bilateral Breast Cancer

Abstract

A personal history of breast cancer is a well established risk factor for subsequent new primary breast tumors. The annual incidence is 0.5-1.0%, 2 to 6 times higher than the incidence of normal women in Western countries to develop primary breast cancer. The 10-year cumulative incidence is around 6-11%. The early age of diagnosis, family history of breast cancer, estrogen receptor status, lobular carcinoma histology, previous radiotherapy and a lack of tamoxifen treatment are thought to be risk factors of bilateral breast cancer. Our investigation also shows menopause, invasive lobular carcinoma, and previous chemotherapy and/or radiotherapy to be risk factors of developing bilateral breast cancer, and tamoxifen therapy to be a protective factor. Regarding prognosis, previous studies comparing survivals between Western women with bilateral and those with unilateral breast cancer have yielded inconsistent results. However, recent reports from a large Sweden cohort and our study have shown that women with metachronous bilateral breast cancer had a worse survival as compared with those with unilateral breast cancer and synchronous bilateral breast cancer. Taiwanese women had a poorer survival than Swedish women. Chemotherapy showed no significant effects on survival in Taiwanese women.