Clinical efficacy of accelerated partial-breast irradiation in treatment of ER-negative breast cancer: Results of a matched pair analysis.

70 Background: To assess outcomes of ER-negative breast CA pts treated with APBI, a matched-pair analysis was performed to determine efficacy of APBI vs whole breast RT (WBRT) from a single institution. Methods: From over 1650 pts treated with BCT from 1980-2013, a cohort of ER[-] pts treated with APBI or WBRT were investigated. Matched-pair analysis with a 1:1 ratio paired 79 APBI with 79 WBRT pts, all ER[-] (total:158). Match criteria included follow-up (FU) > 1.0 yr, stage, & age +/- 5 yrs. Outcomes analyzed included local recurrence (LR), true recurrence/marginal miss (TRMM), regional recurrence (RR), distant metastases (DM), disease-free (DFS), cause-specific (CSS), and overall survivals (OS). Results: As for clinical-pathological traits, no significant differences were noted for age (p=0.302), T-stage (p=1.000), tumor size (p=0.721), N-stage (p=0.062), use of chemoRx (p=0.747), endocrine Rx(p=0.408) or Herceptin (p=1.00). Per ASTRO Guidelines, no differences were seen in cautionary or unsuitable [Un...