Contralateral breast cancer: clinical characteristics and impact on prognosis.

PURPOSE: To determine the characteristics of patients with unilateral breast cancer who subsequently develop contralateral breast cancer (CBC), to assess their prognosis relative to patients who do not develop a CBC, and to assess the feasibility of using conservative surgery (CS) and radiotherapy (RT) to treat CBC. MATERIALS AND METHODS: Of 1,624 women treated with CS and RT for unilateral stage I or II breast cancer at the Joint Center for Radiation Therapy, 77 developed an invasive CBC. Sixty-two CBCs were treated with CS and RT. The median follow-up duration was 95 months from the time of initial breast cancer diagnosis, and 63 months from CBC diagnosis. RESULTS: The cumulative actuarial rate of CBC was 7.0% at 10 years, and the annual incidence rate for CBC was relatively constant. Young age predicted for CBC. When age was analyzed by decade the relative risk (RR) for older patients compared with younger patients was 0.79 (95% confidence interval CI, 0.62 to 1.01). The presence of lobular carcinoma in situ (LCIS), higher tumor stage, and lack of adjuvant systemic therapy also predicted for CBC with borderline significance. Multivariate analyses showed that CBC was associated with a statistically significant greater likelihood of local recurrence (LR) or distant recurrence (RR, 1.68; 95% CI, 1.03 to 2.71), and distant-only recurrence (RR, 2.17; 95% CI, 1.28 to 3.69). Among assessable patients treated with bilateral RT, 28 of 31 ipsilateral and 11 of 11 contralateral breasts had an excellent or good overall cosmetic outcome at 5 years, and treatment-related complications were minimal. CONCLUSION: We conclude that (1) young age is associated with a greater likelihood of CBC, (2) patients who develop a CBC have a greater subsequent risk of distant relapse as compared with patients without CBC, and (3) it is feasible to deliver sequential nonoverlapping bilateral RT without compromising the cosmetic outcome or increasing complications.