Background: The clinical significance of bilateral breast cancer is unclear and its influence on prognosis is controversial. We assessed the impact of synchronous and metachronous bilateral breast cancer on the prognosis compared with unilateral breast cancer.
Methods: Between January 1, 1960 and December 31, 2001, 1,214 women were treated for primary operable breast cancers. Thirteen (1.1%) had synchronous bilateral breast cancer; 33 (2.7%) had a metachronous contralateral breast cancer. We compared age at operation, menopausal status, clinical stage, tumor size and histology, lymph node status, hormone receptor status, and use of adjuvant chemotherapy or hormone therapy, and we analyzed the impact of these factors on recurrence and survival in the 46 patients with bilateral breast cancer and the 1,168 patients with unilateral breast cancer.
Results: The 5-and 10-year disease-free survival rates, respectively, were 65% and 65% in metachronous cases, 85.7% and 64.3% in synchronous cases, and 77.9% and 72.1% in unilateral cases. There was no significant difference in overall survival among the three groups. On multivariate analysis, metachronous bilaterality, tumor size, lymph node status and adjuvant hormone therapy were each independent risk factors for recurrence, whereas bilaterality of breast cancer did not influence overall survival.
Conclusions: Our data suggest that metachronous bilateral breast cancer is associated with shorter disease-free survival than synchronous bilateral or unilateral breast cancer, although overall survival does not differ among the 3 groups. Patients with metachronous bilateral breast cancer should be followed particularly closely in order to detect recurrence early and maximize quality of life.