2708 - Impact of COVID on Utilization of Hypofractionation in Node-Positive Breast Cancer Treatment

R. P. McDougall¹, Y. Shi², J. R. Gabriel¹, M. Serafini², C. Morrison³, J. R. Robbins⁴, C. C. Hsu³, and L. Wang Jr³; ¹University of Arizona, Tucson, AZ, ²University of Arizona Cancer Center, Tucson, AZ, ³University of Arizona - Department of Radiation Oncology, Tucson, AZ, ⁴University of Arizona, College of Medicine-Tucson, Department of Radiation Oncology, Tucson, AZ

Purpose/Objective(s): The COVID-19 pandemic significantly changed radiation dosing trends. This is especially true in breast cancer management. Hypofractionation data for regional nodal radiation dates back to the START A/B trials showing hypofractionation (HF) is noninferior to conventional fractionation (CF). Previously published data from a large Canadian academic institution found that there was a dramatic rise in the use of hypofractionated regional nodal irradiation (RNI) in 2020. Changes in fractionation in patients requiring RNI in the US from COVID remains to be determined. Materials/

Methods: The National Cancer Database (NCDB) was queried to identify all non-metastatic N1-N3 breast cancer patients from 2015-2021 with 2015-2019 defined as pre-COVID and 2020-2021 defined as post-COVID. HF was categorized as 21 fractions or less and CF was >21 fractions. This is based off of acceptable HF RNI regimens of 15 or 16 fractions with up to a 5 fraction boost. Chi-square, ANOVA, and binary logistic regression tests were used to compared the two groups.
Results: A total of 171,590 patients met inclusion criteria with 1115,321 treated pre-COVID and 56,269 treated post-COVID. Patients were significantly more likely to be treated with HF post-COVID than pre-COVID (22.2% vs 12.8% p<0.001). HF increased across both academic (12.2% vs 22.1% p<0.001) and community (13.9% vs 23.9% p<0.001) institutions from pre- to post-COVID. A similar percentage of patients 70 and older were treated pre- and post-COVID (19.5% vs 19.7%, p=0.278). Patients 70 and older were more likely to be treated with HF post-COVID than those <70 however (31.6% vs 20.0%, p<0.001). The proportion of White patients decreased slightly (79.7% vs 78.0%, p<0.001) compared with a slight increase in proportion of Black and Other patients treated from pre- to post-COVID. Patients identifying as neither White or Black were more likely to receive HF compared with White or Black patients (12.0% vs 10.7% vs 10.6% respectively, p<0.001). Patients with a Charlson-Deyo Score (CDS) of 2 or higher were also more likely to receive hypofractionation post-COVID compared with those with a score of 0 or 1 (27.9% vs 22.7% vs 21.8%, p<0.001). Binary logistic regression modeling evaluated HF use with T-staging, N-staging, age 70 or older, CDS, facility type, and COVID, with post-COVID and age 70 or older were found to have the highest odds ratio of receiving HF (1.927 and 1.783 respectively, p<0.001).
Conclusion: In women with node-positive, nonmetastatic breast cancer, there was a significant increase in the use of hypofractionated radiation in the post-COVID era. This is more pronounced in elderly patients as well as those with more comorbidities.