Association between tumor stage of first non-metastatic breast cancer and second contralateral breast cancer.

Abstract

260 Background: Female breast cancer survivors have an average lifetime risk of 4-8% to develop a contralateral breast cancer (CBC).It is unclear if the tumor stage of the first breast cancer is associated with the development of a second CBC. Methods: We performed a retrospective analysis of women who had a presenting diagnosis of non–metastatic breast cancer treated at MD Anderson Cancer Center between January 1997 and December 2013. Demographic, clinical, pathologic and treatment information were obtained from an institutional database. We excluded male patients, those treated outside MD Anderson, patients who underwent bilateral mastectomy, and those with unknown tumor characteristics. The primary endpoint was the development of CBC. The time to CBC was measured from the date of diagnosis of the first breast cancer. Patients who did not develop CBC were censored at death, or if alive, at the most recent follow-up visit. Index tumor stages were categorized as 0, I, II and III. Results: We analyzed 8,770 patients (median follow-up of 5.4 years), among whom 259 (3.0%) developed a CBC. The median follow-up time for stages 0-III was 4.9, 7.2, 5.2 and 3.9 years, respectively. The proportion of patients who developed a CBC by the stage of the index breast cancer was: stage 0: 0/403 (0.0%); stage I: 115/2,143 (5.4%); stage II: 110/4,220 (2.6%); stage III: 34/2,004 (1.7%). The overall median [quartile (Q) 1, Q3] time to the development of CBC was 3.2 (1.2, 6.3) years (stage 0: 0 (0.0, 0.0); stage I: 3.0 (1.2, 6.3); stage II: 4.4 (1.3, 6.9); stage III: 1.6 (0.8, 5.1) years). Conclusions: Patients with stage 0 breast cancer appear to have lower risk of developing a second CBC compared to women presenting with invasive disease. A more detailed analysis of this observation, including incorporation of hormone receptor status and receipt of endocrine therapy, is warranted to determine whether this observation suggests differing biologic risks or treatment/selection bias.