ASTRO 2024: Hypofractionation With Simultaneous Integrated Boost in Breast Cancer

By: Vanessa A. Carter, BS
Posted: Monday, October 7, 2024

The HYPOSIB trial (ARO 2013-05), conducted by David Krug, MD, of University Hospital Hamburg-Eppendorf, Germany, and colleagues, investigated the use of moderate whole-breast hypofractionation combined with simultaneous integrated boost irradiation in patients with breast cancer. The results of this trial, presented during the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 4), suggest this radiotherapy combination may become a standard-of-care treatment after breast-conserving surgery.

A total of 2,179 patients were randomly assigned 1:1 to receive either 40 Gy to the breast and 48 Gy to the tumor bed in 16 fractions or the physician’s choice of treatment. The primary endpoint was disease-free survival, and secondary endpoints included overall survival, toxicity, quality of life, local tumor control, locoregional tumor control, and cosmesis. A 5-year disease-free survival rate of 86.4% was assumed in the control arm at trial initiation, with a 5% noninferiority margin.

At the median follow-up of 52.9 months, 141 patients had at least one disease-free survival event, and 75 of these participants received the experimental combination. Of 31 patients who experienced local recurrence, 16 were in the experimental arm. Disease-free survival at 5 years was similar in both cohorts, supporting the noninferiority of hypofractionated whole-breast irradiation plus simultaneous integrated boost over conventional radiation (92.0% vs 92.2%). 

The 5-year local tumor control rates were also comparable in the experimental and control arms at 98.2% and 98.0%, respectively. Overall survival at 5 years was numerically higher in the experimental arm (98.2%) than in the control arm (97.9%), but it was not statistically significant.

Grade 2 fibrosis was more common among patients on the physician’s choice of treatment (8.4%) than in those on the radiation combination (7.3%). However, grade 2 telangiectasia was reported in the same number of patients (1.5% each) in each treatment arm.

Disclosure: For Dr. Krug’s full disclosures, visit astro2024.eventscribe.net.

2024 ASTRO Annual Meeting

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