Survival and toxicity after breast-conserving surgery and external beam reirradiation for localized ipsilateral breast tumour recurrence: A population-based study.

Breast-conserving surgery followed by reirradiation for a localized ipsilateral breast tumour relapse may increase the radiation dose delivered to the heart and result in a greater risk of cardiac adverse events. This study aimed to compare the incidence of cardiac mortality in patients treated for a localized ipsilateral breast tumour relapse, either with breast-conserving surgery followed by reirradiation or with total mastectomy between 2000 and 2020. All patients treated for a primary non-metastatic breast cancer with breast-conserving surgery and adjuvant radiotherapy were identified in the Surveillance, Epidemiology, and End Results (SEER) program database, and those who subsequently experienced a localized ipsilateral breast tumour relapse treated with breast-conserving surgery and reirradiation ("BCS + ReRT" group, n = 239) or with total mastectomy ("TM" group, n = 3127) were included. The primary objective was to compare the cardiac mortality rate between the patients who underwent breast-conserving surgery followed by reirradiation and total mastectomy. Secondary endpoints were overall survival and cancer specific survival. Cardiac mortality was significantly higher in patients treated with breast-conserving surgery followed by reirradiation (hazard ratio [HR]: 2.40, 95% confidence interval [95% CI]: 1.19–4.86, P = 0.006) in univariate analysis; non-statistically significant differences were observed after adjusting for age, laterality and chemotherapy on multivariate analysis (HR: 1.96, 95% CI: 0.96–3.94, P = 0.067), age being the only confounding factor. A non-statistically significant difference towards lower overall survival was observed in patients who had breast-conserving surgery followed by reirradiation compared with those who underwent total mastectomy (HR: 1.37, 95% CI: 0.98–1.90, P = 0.066), and no differences were observed in terms of cancer specific survival (HR: 1.01, 95% CI: 0.56–1.82, P = 0.965). In this study, the incidence of cardiac mortality was low, and breast-conserving surgery followed by reirradiation did not independently increased the risk of cardiac mortality for a localized ipsilateral breast tumour relapse. [ABSTRACT FROM AUTHOR]