Abstract 1108: Comparative analysis of hypofractionated and conventional fractionated radiotherapy on acute skin toxicity in a multiracial/ethnic breast cancer population
Authors: Zhang Veronica Y. , Takita Cristiane , Wright Jean L. , Zhao Wei , Reis Isildinha M. , Lee Eunkyung , Hu Jennifer J. 
Published: June 2023

Abstract
Purpose: Hypofractionated radiotherapy (HF-RT) has replaced conventional fractionated RT (CF-RT) and becomes the new standard practice for adjuvant RT due to shorter overall treatment time, similar local control, survival outcomes, and normal tissue toxicities. However, most studies did not provide evidence to support the use of HF-RT in minorities with worse RT-related acute skin reactions. Therefore, this study aims to assess whether HF-RT leads to less severe acute skin toxicity compared to CF-RT in a tri-racial/ethnic population with 87% minorities.
Method: A total of 490 breast cancer patients who underwent RT following either lumpectomy or mastectomy were divided into three groups based on RT type and dosage. (A) 373 patients received CF-RT and 60+ Gy; (B) 58 patients received CF-RT and &lt;60 Gy; (C) 59 patients received HF-RT and &lt;60 Gy. Acute skin toxicities immediately after RT were assessed using Common Toxicity Criteria for Adverse Events (CTCAE, v. 3) scale grades 0-1 or ≥ grade 2. Univariable and multivariable analyses were used to evaluate the associations between skin toxicity at post-RT and clinical characteristics, RT groups, and inflammatory biomarker C-reaction protein (CRP).
Result: In all breast cancer patients (312 Hispanic whites, 99 African Americans, 63 non-Hispanic whites, and 16 others), HF-RT was associated with a lower risk of grade 2+ skin toxicity (p&lt;0.01). Grade 2+ skin toxicity occurred in 65.4%, 48.3%, and 28.8% of Groups A, B, and C, respectively. Patients with grade 0-1 skin toxicity had lower CRP levels/inflammation than those with grade 2+ skin toxicity (p=0.059). In multivariable logistic regression analysis, RT-induced grade 2+ skin toxicity was significantly associated with pre-and post-RT CRP (odds ratio [OR]=2.12; 95% CI=1.18, 3.78; p=0.011), BMI ≥ 30 kg/m2 (OR= 2.20; 95% CI=1.32, 3.68; p=0.003) and RT Group C (HF and &lt;60 Gy) (OR=0.33; 95% CI=0.18, 0.64; p&lt;0.001).
Conclusion: This study is the first to evaluate acute skin toxicity induced by HF-RT vs. CF-RT in a multiracial breast cancer population with 87% minorities. The results show that BMI, RT group, and post-RT CRP change are associated with an increased risk of grade 2+ skin toxicity. Breast cancer received HF-RT had a lower risk of grade 2+ skin toxicity compared to CF with an equivalent dosage, indicating additional causes of lessened skin toxicity by HF-RT than dosage. With a limited sample size, our marginally significant data shows promising results that lower inflammatory biomarker levels in HF-RT vs. CF-RT as the potential mechanism related to lower HF-RT-induced skin toxicity but will need validation in future larger studies.
Citation Format: Veronica Y. Zhang, Cristiane Takita, Jean L. Wright, Wei Zhao, Isildinha M. Reis, Eunkyung Lee, Jennifer J. Hu. Comparative analysis of hypofractionated and conventional fractionated radiotherapy on acute skin toxicity in a multiracial/ethnic breast cancer population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1108.