Ultra Hypo-fractionated Adjuvant Whole Breast Radiation Therapy With Simultaneous Integrated Boost for Early-Stage Breast Cancer (H-ASSIST)

This study evaluates the rates of radiation-specific toxicity, quality of life, and oncologic outcomes for early-stage breast cancer and ductal carcinoma in situ treated with 5-fraction whole breast irradiation (WBI) with a simultaneous integrated tumor bed boost (SIB). SIB refers to the technique tumor bed boost given at the same time as standard radiation therapy. The FAST-Forward trial previously showed that a 1-week course of radiotherapy had similar effects to the traditional 3-week course for early-stage breast cancer after surgery. Given these favorable results, a 5-fraction WBI regimen is appealing for many patients who wish to minimize the number of treatment visits while still reducing their risk of recurrence. Generally, tumor bed boosts further decrease the risk of recurrence, but in the setting of 5-fraction WBI, a more traditional sequential boost technique is utilized.

Multiple recent studies demonstrate the noninferiority of a simultaneous integrated boost (SIB) approach. This study will include women aged 50 years and older who are recommended to receive whole breast irradiation with a standard dose boost and without regional nodal irradiation. Radiation therapy will consist of 5 fractions delivered every other day (excluding weekends), with a total dose of 26 Gy to the whole breast and a simultaneous integrated boost to a total dose of 30 Gy to the lumpectomy cavity. The primary outcome of this study is to investigate the rate of moderate to marked adverse effects in the breast and chest wall of patients receiving five-fraction whole-breast radiation therapy with a concurrent boost. Radiation-specific toxicity outcomes will be assessed by clinicians and patients at 12 months, along with evaluations of quality of life and oncologic control at 24 months following treatment. It is hypothesized that 5-fraction whole breast irradiation with a simultaneous integrated boost will result in clinically acceptable rates of moderate to marked toxicity relative to historical controls, while providing good quality of life and high rates of disease control.