Outcomes of women with small, early-stage breast cancer in Manitoba from 2006-2011.

Abstract

e12000 Background: The incidence of early-stage breast cancers has increased dramatically over the past decades. Treatment decisions for patients with stage I breast cancers are challenging, as there are significant variations in outcomes based on biologic subtypes. The objectives were to describe the distribution, molecular phenotypes, management, and long-term outcomes of women with early-stage breast cancer (T1mic/T1a/T1b N0 M0) in Manitoba from 2006-2011. Methods: Using the Manitoba Cancer Registry, we created a retrospective cohort of patients with primary breast cancer of ≤1.0 cm, diagnosed between 2006 and 2011. Data included patient demographics, tumour size, treatment modalities (surgery, radiotherapy, chemotherapy and trastuzumab), estrogen-receptor (ER) and progesterone-receptor (PR) status, and human epidermal growth factor receptor 2 (HER2) status. Node-positive cancers were excluded. Patient outcomes were evaluated, including rates of recurrence and overall survival using univariate and multivariable models. Kaplan-Meier curves and cumulative incidence curves were used to illustrate overall survival and recurrence, respectively. Results: Our study included 733 women. Mean age at diagnosis was 62. ER/PR positivity and HER2 positivity (HER2+) were 84% and 8.9%, respectively. Tumours were: T1mic in 14.0%, T1a in 19.1%, and T1b in 66.9%. 98% of patients had surgery, 60% had adjuvant radiation, 3.8% received trastuzumab, and 11% received chemotherapy. The adjusted hazard ratio (HR) for disease recurrence for patients with HER2+ versus HER2- status was 4.31 (95% CI, 2.18 to 8.50; P = 0.0001), and the HR for overall survival was 1.63 (95% CI, 0.72 to 3.67; P = 0.2402). The HR for disease recurrence in HER2+ patients receiving trastuzumab versus HER2+ patients who did not receive trastuzumab was 1.92 (95% CI, 0.61 to 5.97; P = 0.2621). Conclusions: HER2-positivity appears to be an important risk factor for recurrence in small, early-stage breast cancers. In our cohort, trastuzumab did not appear to reduce the risk of recurrence compared to those who did not receive it. This may be due to limited power and selection bias, in which patients with higher risk cancers received trastuzumab.