Survival after Breast-Conserving Surgery with Whole Breast or Partial Breast Irradiation in Women with Early Stage Breast Cancer: A SEER Data-base Analysis.

Randomized clinical trials have demonstrated equivalency in survival outcomes for early stage breast cancer patients treated with either mastectomy or breast-conserving surgery (BCS) with radiation. Recent, state-level data confirm comparable survival outcomes. Using Surveillance Epidemiology and End Research (SEER) data, we sought to evaluate survival outcomes among patients with early stage breast cancer treated with mastectomy, BCS with whole breast irradiation (BCS + WBI), or BCS with accelerated partial breast irradiation (BCS + APBI). Data on women 50 years or older diagnosed with a node negative invasive breast cancer (≤3 cm in size) between 1995 and 2009 were extracted from the SEER data base. Women treated with mastectomy alone or BCS with radiation were eligible for analysis. Kaplan-Meier estimates and Cox proportional hazard models were used to compare overall survival (OS) and cancer-specific survival (CSS) among the treatment groups. 150,171 women fulfilled inclusion criteria. OS was significantly improved among women treated with BCS and WBI or BCS and APBI compared to mastectomy alone. Adjusted hazard ratios for death in BCS with WBI or APBI (versus mastectomy alone) were 0.73 (95% CI: 0.71, 0.76) and 0.68 (95% CI: 0.58, 0.79), respectively. Adjusted CSS was also significantly improved in patients treated with BCS and WBI (HR 0.80, 95% CI: 0.76, 0.85) as compared to mastectomy. BCS with radiation (WBI or APBI) was associated with significantly improved OS and CSS, versus mastectomy alone. These results support the use of BCS with WBI or APBI (in well selected patients) for the treatment of breast cancer.