The clinical significance of bilateral breast cancer is unclear and its influence on prognosis is controversial, whether contralateral breast cancer occurs synchronous or metachronous. Our purpose is to assess the impact of bilateral breast cancer on prognosis and compared it to unilateral breast cancer. Methods

We included 9,327 patients who diagnosed breast cancer and treated at Asan Medical Center from 1990 to 2007. Bilateral breast cancer was classified as synchronous in patients with a second breast cancer diagnosed within 6 months after the first breast cancer and as metachronous if the second breast cancer occurred more than 6 months after the first. To compare clinical features, we used more advanced-stage tumor in synchronous cases and the first tumor in metachronous cases. The follow-up cut-off date of this study was December 2009 and median value of follow-up was 59 months. This study was performed by medical records review retrospectively. Results

117 (1.3%) had synchronous breast cancer and 114 (1.2%) had metachrnous breast cancer. Except menopausal status, there were no significant differences for clinical features between the patients with unilateral breast cancer and synchronous bilateral breast cancer. Patients with bilateral metachronous breast cancer were significantly younger at the time of first diagnosis and had more often a highly increased familial risk. And women who developed metachronous cancer underwent more often mastectomy for their first tumor.

Patients with synchronous (74.2%) or metachronous bilateral breast cancer (77.7%) had the same risk of death from breast cancer as patients with unilateral breast cancer. (82.7%) (10 years overall survival, p=0.703) Also, disease-free survival was no difference between these three groups. But when we analyzed disease-free survival according to recurrence pattern, patients with metachronous breast cancer had a higher risk of loco-regional recurrence, significantly, compared with other groups. Conclusion

Patients with metachronous breast cancer developed more loco-regional recurrence than patients with unilateral disease or synchronous disease, but this recurrence didn't affect overall survival. Bilaterality of breast cancer is not associated with impaired overall survival.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-10-05.