Bilateral synchronous breast cancer: A population-based study of characteristics, method of detection, and survival

Background. The frequency of bilateral synchronous breast cancer (BSBC) is reportedly about 1%-3%, but there is limited information from Population-based cancer registries regarding the clinical and prognostic features of these cancers. Methods. The population-based Connecticut Tumor Registry (CTR), which is part of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program of registries, was used to identify BSBC (ie, a second cancer diagnosed within 3 months of the first). Information was obtained. on the method of detection of BSBC, and clinical characteristics and survival (through 2000) were compared with unilateral cases. Results. Of 15,542 patients reported to the CTR, 300 (1.9%) had BSBC. BSBC was detected most often by mammography of both breasts (35%) or contralateral mammography after a palpable first cancer (18%). Compared to unilateral cases, BSBC patients did not differ in age or stage at diagnosis, but lobular histology was statistically significantly more frequent and use of total mastectomy (vs lesser surgery) was more common. Although length of follow-up was limited, risk of death was statistically, significantly higher among BSBC than unilateral patients. Among BSBC patients, risk of death was higher among those with cancers detected by breast exam/symptoms versus mammography. Conclusions. While uncommon, BSBCs differ from unilateral cancer in histology and survival, and their study emphasizes the opportunity for detection of contralateral cancers at an early stage.