While boosts were permitted in trials of ultrahypofractioned whole breast radiation, they were typically conventionally fractionated boosts. SHIFT was a single arm, phase 2 study that evaluated ultrahypofractionated whole breast RT (26 Gy in 5 fractions) with a sequential ultrahypofractionated boost (10.4 Gy in 2 fractions) when indicated. It included 217 patients with Tis-3 N0-1mi breast cancer. Most (96.3%) received a boost, and multibeam IMRT was used for all plans. There were no grade 3 adverse events, and only 7.4% had grade 2 adverse events. Dermatitis, the most frequent adverse event, peaked during week 2 (35% grade 1, 0.5% grade 2). Any grade breast pain was seen in 32.3%, and any grade edema was seen in 27.2%. There were no recurrences, although median follow up was short at 28 months. | Zheng, Int J Radiat Oncol Biol Phys 2026
