Clinical characteristics of metachronous contralateral breast cancer following diagnosis interval

Purpose: As the population of breast cancer survivors increasing, concerns for second primary cancer has been grown. The most frequent second primary tumor after breast cancer diagnosis is contralateral breast cancer (CBC). CBC developed less than five years showed poor prognosis. However, in Korea, little is known about the clinical characteristics of CBC regarding diagnosis interval. Methods: We retrospectively reviewed medical records of the patients who diagnosed stage I-III breast cancer from three tertiary medical centers and identified CBC patients. We divided those patients into early-onset CBC (ECBC), which diagnosed within five years, and late-onset CBC (LCBC) which developed after five years since primary cancer. We also searched available published original articles regarding bilateral breast cancer in Korean population for comparison. Results: Between January 2003 and December 2013, a total of 3,695 patients were included. During follow up, 22 patients diagnosed as CBC. Mean age of ECBC (n=10) was 50.9±15.4 and that of LCBC (n=12) was 45.5±14.3. There were no significant difference between ECBC and LCBC in menopausal status, menarcheal age, family history of breast cancer, clinical stage, and pathologic characteristics. ECBC was related worse disease-free survival than LCBC (P=0.017). With meta-analysis of published reports in Korean population, the incident rate calculated from person-month was 0.06. Conclusion: ECBC showed poor prognosis than LCBC with cut-off at five years since diagnosis of primary breast cancer, and it was consistent with Western reports. Intensive treatment might be needed in those patients with ECBC.