Is repeat breast conservation possible for small ipsilateral breast cancer recurrence?

Most cases of ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery (BCS) involve small tumors. Although a few guidelines recommend mastectomy, several patients prefer repeat BCS (re-BCS). This study aimed to compare re-BCS and mastectomy in terms of prognosis in patients with IBTR and to identify candidates for re-BCS.The data of patients with small IBTR between 1999 and 2015 were obtained from the Surveillance, Epidemiology, and End Results database. The outcomes of interest were overall survival (OS) and breast cancer-specific survival (BCSS). Multivariable Cox proportional hazards regression models and propensity score matching were applied.Of the 3648 patients with IBTR, 2831 (77.6%) underwent mastectomy and 817 (22.4%) underwent re-BCS. The multivariate Cox model showed that re-BCS was associated with a worse OS (hazard ratio [HR], 1.342; 95% confidence interval [CI], 1.084-1.663) and BCSS (HR, 1.454; 95% CI, 1.004-2.105) compared with mastectomy. The omission of radiation after re-BCS was associated with worse survival overall and especially in patients with estrogen receptor (ER)-negative IBTR (HR, 1.384; 95% CI, 1.110-1.724; and HR, 1.577; 95% CI, 1.075-2.314, respectively). No statistically significant differences were observed in the OS and BCSS between re-BCS with radiation and mastectomy. Subgroup analysis indicated that the surgical approach was not an independent factor for survival in the ER-positive patients with IBTR.Re-BCS should be considered with caution in patients with small IBTR. However, a positive ER status can be an important factor for choosing re-BCS, and radiation therapy may improve oncological safety after re-BCS.Repeat breast-conserving surgery (re-BCS) was investigated to determine if it is safe for patients with small ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery (BCS). This population-based cohort study included 2831 patients with small IBTR. Re-BCS was associated with a worse overall survival and breast cancer-specific survival compared with mastectomy. Further analysis found that the IBTR estrogen receptor status was an important basis for choosing re-BCS, and radiation may improve oncological safety after re-BCS.