Are We Missing Acute Toxicities Associated with Hypofractionated Breast Irradiation? A Report from a Large Multi-Center Cohort Study

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Conference Proceeding

Publication Date


Publication Title

Int J Radiat Oncol Biol Phys


Purpose/Objective(s): The efficacy and long-term safety of hypofractionated whole breast irradiation (HF-WBI) has been established through multiple randomized trials. However, data on acute toxicities associated with HF-WBI remain more limited. Since 2013, our group has prospectively collected data on acute toxicities associated with HF-WBI based on weekly evaluation during treatment and assessment at 1 month after completion of radiotherapy. In October 2015, we intentionally shifted the post-treatment assessment time-point from 1 month to 2 weeks post-completion of treatment. This change was intended to evaluate whether a closer follow-up (f/u) might result in the detection of otherwise unobserved acute toxicities for patients receiving HF-WBI. In this study we report whether 2-week f/u has resulted in increased sensitivity for detecting acute toxicity as compared with 4-wk f/u. Materials/Methods: We prospectively compared acute toxicity for patients treated with HF-WBI at 25 participating institutions. We compared patients treated between 1/1/2013 and 8/31/2015 (before 2-week f/u up was adopted – “4 wk f/u cohort”) to patients treated between 1/1/2016 – 8/31/2018 (after adoption of a 2-week f/u – “2 wk f/u cohort”). Acute toxicity was considered the maximum reported composite toxicity from 7 days prior to the completion of radiotherapy until 42 days (6 weeks) following completion. Composite toxicity was defined as self-reported or physician-assessed moderate or severe breast pain, and/or physician-assessed presence of moist desquamation. Multivariable logistic regression models were used to assess difference in toxicity by cohort using ASTRO HF-WBI 2018 Guideline v. 2011 Guideline, and further adjusted for BMI, breast volume, race, presence of comorbidity, smoking status, and use of IMRT. Results: 2243 patients who received post-lumpectomy radiation and boost were analyzed, 1369 patients in the 2-wk f/u cohort and 874 in the 4-wk f/u cohort. Occurrence of composite acute toxicity was similar between the 2 cohorts, 28.4% for 2-wk f/u cohort vs 26.9% for the 4-wk f/u cohort, adjusted p=0.66. When analyzing only patients who met all ASTRO HF-WBI Guideline v. 2011 criteria, no difference in acute toxicity was noted; 26.5% with 2-wk f/u vs 25.0% with 4-wk f/u, adjusted p=0.83. Finally, with 2 wk f/u compared with 4 wk f/u, additional acute toxicities were not detected for patients who were younger <50 years (p=0.72), received chemotherapy (p=0.93), had ductal carcinoma in-situ (p=0.13), or had separation >25 cm, (p=0.43), yet otherwise guideline compliant. Conclusion: A closer post-treatment follow-up for patients receiving HF-WBI did not reveal a significant increased incidence of acute toxicities at 2 weeks compared to 4 weeks. This study provides physicians and patients with additional data on the safety and tolerability of HF-WBI and the appropriateness of the interval of follow-up.





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