Comparison of clinicopathological characteristics and prognoses between bilateral and unilateral breast cancer

Purpose The clinical significance of bilateral breast cancer is unclear and its influence on prognosis is controversial. We compared the characteristics and prognosis of bilateral breast cancer and unilateral breast cancer. Methods Our study included 4,183 patients with breast cancer who were treated at Sun Yat-sen University Cancer Center between January 1, 2000, and December 31, 2007. Bilateral breast cancer was categorized as synchronous (within 3 months) or metachronous (diagnosed after 3 months of first cancer). SPSS was used for data analysis. Results 106 (2.5%) and 31 (0.7%) patients were diagnosed with metachronous and synchronous bilateral cancer. Women with bilateral cancer had more frequent postmenopause, HER-2 negativity, and advanced disease than in patients with unilateral cancer. Young age at diagnosis, invasive lobular carcinoma, ER/PR negativity, HER-2 positivity, radiation, large tumor size ( T > 5 cm), and stage III disease of the first cancer were risk factors for contralateral cancer. The 5-year disease-free survival and overall survival rates were 76 and 83% for unilateral cancer, while 32 and 72% for bilateral cancer ( P = 0.000 for both). Conclusions Bilateral cancer was associated with shorter disease-free survival and overall survival than unilateral cancer. The prognosis of metachronous bilateral cancer, especially those diagnosed within 2 years after the first cancer was significantly worse than synchronous bilateral cancer.