Background: This phase III post-NC trial will evaluate if CWRNRT post Mx or whole breast irradiation (WBI) with RNRT after BCS significantly reduces the invasive breast cancer recurrence-free interval (IBCR-FI) rate in pts presenting with positive Ax nodes that are negative after NC. Secondary aims are OS, LRR-FI, DRFI, DFS-DCIS, and second primary cancer as well as comparing RT effect on cosmesis in reconstructed Mx pts. Correlative science examines RT effect by tumor subtype, molecular outcome predictors for residual disease pts, and predictors for the degree of reduction in loco-regional recurrence. Methods: Clinical T1-3, N1 IBC pts with positive Ax nodes (FNA or core needle biopsy) complete ≥ 12 wks of NC (anthracycline and/or taxane). HER2-positive pts receive anti-HER2 therapy (tx). After NC BCS or Mx is performed with a sentinel node biopsy ( ≥ 3 nodes) and/or Ax dissection with histologically negative nodes. ER/PR and HER-2 neu status before NC is required. Pts receive required systemic tx. Radiation credentialing with a facility questionnaire and a case benchmark is required. Randomization for Mx pts is to no CWRNRT or CWRNRT and for BCS pts to WBI or WBI RNRT. Statistics: 1636 pts to be enrolled over 5 yrs with definitive analysis at 7.5 yrs. Study is powered at 80% to test that RT reduces the annual hazard rate of events for IBCR-FI by 35% for an absolute risk reduction in the 5-yr cumulative rate of 4.6%. Intent-to-treat analysis with 3 interim analyses at 43, 86, and 129 events, with a 4th/final analysis at 172 events will occur. Accrual as of 1/15/15 is 96. Pt-reported outcomes focusing on RT effect will be provided by 736 pts before randomization and at 3, 6, 12, and 24 mths. Support: U10 CA 12027, 69651, -37377, -69974; -2166; -180868, -180822; CA189867; Elekta Clinical trial information: NCT01872975