Survival in stage I-III breast cancer patients by surgical treatment in a publicly funded health care system

Background: Recent investigations of breast cancer survival in the United States suggest that patients who receive mastectomy have poorer survival than those who receive breast-conserving surgery (BCS) plus radiotherapy, despite clinically established equivalence. This study investigates breast cancer survival in the publicly funded health care system present in Alberta, Canada. Patients and methods: Surgically treated stage I-III breast cancer cases diagnosed in Alberta from 2002 to 2010 were included. Demographic, treatment and mortality information were collected from the Alberta Cancer Registry. Unadjusted overall and breast cancer-specific mortality was assessed using Kaplan-Meier and cumulative incidence curves, respectively. Cox proportional hazards models were used to calculate stage-specific mortality hazard estimates associated with surgical treatment received. Results: A total of 14 939 cases of breast cancer (14 633 patients) were included in this study. The unadjusted 5-year all-cause survival probabilities for patients treated with BCS plus radiotherapy, mastectomy, and BCS alone were 94% (95% CI 93% to 95%), 83% (95% CI 82% to 84%) and 74% (95% CI 70% to 78%), respectively. Stage II and III patients who received mastectomy had a higher all-cause (stage II HR = 1.36, 95% CI 1.13-1.48; stage III HR = 1.74, 95% CI 1.24-2.45) and breast cancer-specific (stage II HR = 1.39, 95% CI 1.09-1.76; stage III HR = 1.79, 95% CI 1.21-2.65) mortality hazard compared with those who received BCS plus radiotherapy, adjusting for patient and clinical characteristics. BCS alone was consistently associated with poor survival. Conclusions: Stage II and III breast cancer patients diagnosed in Alberta, Canada, who received mastectomy had a significantly higher all-cause and breast cancer-specific mortality hazard compared with those who received BCS plus radiotherapy. We suggest greater efforts toward educating and encouraging patients to receive BCS plus radiotherapy rather than mastectomy when it is medically feasible and appropriate.