Ultra-Hypofractionated Whole-Breast Irradiation With or Without Simultaneous Integrated Boost Using Helical Tomotherapy for Early-Stage Breast Cancer: A Real-World Dosimetric and Clinical Outcome Study

<b>Background</b>: Ultra-hypofractionated whole-breast irradiation (WBI) delivering 26 Gy in five fractions has been established as a standard of care following the FAST-Forward trial. However, real-world data addressing advanced delivery techniques and the feasibility of incorporating a simultaneous integrated boost (SIB) remain limited. <b>Methods</b>: We retrospectively analyzed 40 patients with early-stage breast cancer (pT1-2N0M0) treated with breast-conserving surgery, followed by ultra-hypofractionated WBI using helical tomotherapy. Patients received either WBI alone (26 Gy in five fractions) or WBI with an SIB to the tumor bed (29-30 Gy in five fractions). Dosimetric parameters for planning target volumes (PTVs) and organs at risk (OARs) were evaluated. Acute skin toxicity was assessed using CTCAE version 5.0. <b>Results</b>: The median patient age was 55.7 years. The mean PTV V95% was 97.8%, with excellent hotspot control (PTV V105% < 5% and V107% < 2%). For left-sided tumors, the mean heart dose was 1.67 Gy, and the ipsilateral lung V8Gy remained below 15% in all patients. Acute radiation dermatitis was limited to Grade 0-1 in all cases. At a median follow-up of 14.8 months, both local control and overall survival were 100%. <b>Conclusions</b>: Ultra-hypofractionated WBI delivered using helical tomotherapy, with or without SIB, demonstrates robust dosimetric quality, minimal acute toxicity, and favorable early clinical outcomes in routine clinical practice.