Acute adverse events of hypofractionated whole-breast radiotherapy with a simultaneous-integrated boost - Results from the randomized controlled HYPOSIB-trial (ARO 2013-05).
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- Record sourced from PubMed, PMID 42537852.
- Also identified by DOI 10.1016/j.ijrobp.2026.07.022.
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Abstract
Moderate hypofractionation (HF) is standard of care for adjuvant whole-breast irradiation after breast-conserving surgery (BCS). While boost irradiation has traditionally been administered sequentially (seq) after whole-breast irradiation, a growing amount of data suggests that delivery of a simultaneous integrated boost (SIB) may be equally effective and tolerable. HYPOSIB is a randomized controlled non-inferiority trial enrolling patients with breast cancer after BCS. Patients were randomized 1:1 to HYPOSIB (40 Gy in 16 fractions to the breast with SIB of 48 Gy to the tumor bed) or to the standard arm (investigator's choice: conventionally fractionated radiotherapy (CF) with SIB (CF<sub>SIB</sub>) or CF<sub>seq</sub> or HF<sub>seq</sub>). The focus of this manuscript is the secondary endpoint of selected prespecified acute adverse events (radiation dermatitis, pain, feeling of pressure in the breast - further termed breast discomfort) according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.0 up to 3 months after treatment. From 06/2015 to 01/2019, 2310 patients were enrolled. The analysis set included 2264 consenting patients that received radiotherapy. HYPOSIB resulted in fewer cases with worst grade of radiation dermatitis (grade 2: 25.3% vs. 38.6%; grade 3: 2.3% vs. 3.1). Radiation dermatitis occurred earlier during HYPOSIB but resolved more rapidly. There were more worst grade hot flashes during the HYPOSIB (grade 2: 29.7% vs. 26.0%; grade 3: 8.6% vs. 6.8%). Only 3.3% of hot flashes were judged as radiotherapy-related. Pain and breast discomfort were more frequent during the standard treatment and at later time points after HYPOSIB, mirroring the temporal trends for radiation dermatitis. HYPOSIB in 16 fractions led to a clinically relevant reduction in worst grade radiation dermatitis. There were temporal differences between treatments in the occurrence of radiation dermatitis, pain, and breast discomfort with adverse events occurring and resolving earlier with HYPOSIB.