Abstract P4-12-15: Whole breast radiation therapy completion in early stage breast cancer following lumpectomy
Authors: McClelland Shearwood , Burney Heather N , Zellars Richard C , Rhome Ryan M 
Published: March 2020

Abstract
Introduction: Whole breast radiation therapy (RT) has become standard of care in treatment of early-stage breast cancer following lumpectomy. The impact of standard fractionation versus hypofractionated RT on treatment completion has yet to be examined on a nationwide scale.
Methods: The National Cancer Data Base (NCDB) from 2004-2015 identified early-stage breast cancer patients having undergone lumpectomy. Standard fractionation whole breast radiation was defined as receipt of at least 46 Gray (Gy) in 1.8-2.0 Gy/fraction. Hypofractionated whole breast radiation therapy was defined as receipt of at least 40 Gy in 2.66-2.70 Gy/fraction. A multivariable logistic regression model characterized completion of RT, adjusting for several factors including patient age, race, insurance status, income, percentage of high school graduates in the region, analytic group stage, fractionation type, geographic location of treatment, facility type, and distance from treatment facility.
Results: 105,388 patients with reliable fraction sizes (dose divided by fraction number) were identified, of whom more than 87% completed RT. Compared to patients with a median income of $38,000-$47,999 per year, patients in the lowest median income quartile (less than $38,000 per year) had 1.23 times the odds of not completing RT (OR = 1.23; 95% CI = 1.14-1.32; p &lt; 0.0001). Compared to private insurance, patients with Medicare or Medicaid had 1.23 times the odds of not completing RT (OR = 1.23; 95% CI = 1.18-1.29). More than two-thirds (66.8%) of United States patients with early-stage breast cancer following lumpectomy were treated with standard fractionation compared with 33.2% receiving hypofractionation, yet hypofractionation significantly increased over time (5.2% increase/year; p &lt; 0.0001). RT completion rates were significantly greater following hypofractionation (99.3%) versus standard fractionation (81.0%) on univariable and multivariable analyses, with standard fractionation associated with nearly 37 times the odds of not completing RT compared with hypofractionation [odds ratio (OR) = 36.8; 95% confidence interval (CI) = 32.5-41.7; p &lt; 0.0001] on multivariable analysis. Multivariable analysis revealed that African-American patients (OR = 20; 95% CI = 13.9-28.7; p &lt; 0.0001) and Caucasian patients (OR = 38; 95% CI = 33.2-43.5; p &lt; 0.0001) treated with standard fractionation versus hypofractionation had 20 and 38 times the odds of not completing RT.
Conclusions: The majority of radiation therapy for early-stage breast cancer in the United States has remained standard fractionation, however hypofractionation has increased in popularity with time. Overall, patients treated with standard fractionation had 37 times the odds of not completing RT than those treated with hypofractionation. With the potential of hypofractionation to reduce healthcare costs, RT access disparities, and increase rate of RT completion, a wise approach towards improving healthcare in the United States would be to place more of an emphasis on early-stage breast cancer patients receiving hypofractionated radiation therapy.
Citation Format: Shearwood McClelland III, Heather N Burney, Richard C Zellars, Ryan M Rhome. Whole breast radiation therapy completion in early stage breast cancer following lumpectomy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-15.