First Results of a Phase 2 Trial of Once-Weekly Hypofractionated Breast Irradiation (WHBI) for Early-Stage Breast Cancer.

Purpose: To report early outcome analysis of a prospective institutional phase 2 trial of weekly hypofractionated breast irradiation (WHBI) for patients undergoing breast-conserving surgery (BCS).

Methods And Materials: Patients who underwent BCS for American Joint Committee on Cancer stage 0, I, or II breast cancer with negative surgical margins received whole-breast radiation therapy to 30 or 28.5 Gy in 5 weekly fractions with or without an additional boost.