Background: The American Society for Radiation Oncology’s (ASTRO) Choosing Wisely (CW) initiative recommends against the use of conventional radiation therapy (CRT) in favor of hypofractionation for whole breast radiotherapy in breast cancer (BC) patients. We analyzed the effect of CW on CRT use in older patients with BC. Additionally, factors that may predict CRT were assessed.

Methods: We conducted a retrospective observational cohort study using Surveillance, Epidemiology, End Results-Medicare database including women age >66 years diagnosed with stage I-II BC during 2007-2015 who had lumpectomy and radiation therapy (N=34,507). CRT was defined as ≥4-weeks of radiation therapy. We determined the proportion of patients who received CRT following lumpectomy and conducted an interrupted time-series (ITS) analysis and segmented regression to examine if CW impacted the use of CRT and to estimate the magnitude of change. A multivariable logistic regression was conducted for the post-CW group to identify the significant predictors of CRT use.

Results: During 2007-2015, 79.0% of the study cohort received CRT prior to the launch of CW in September 2013 compared to 75.5% post-CW. ITS analysis showed that there was a significant 0.12 per 100 patients per quarter decrease in the CRT use pre-CW (p<0.0001). However, there was an increase of 0.31 per 100 patients per quarter immediately following the implementation of CW and a significant 0.34 per 100 patients per quarter decrease in the use of CRT resulting from CW (p<0.0001). Being Hispanic, residence in South, Northeast or North Central parts of the US, presence of ≥2 comorbidities, having a large tumor and of low grade, and involvement of regional lymph node and were significant predictors of CRT use.

Conclusion: A reduction of use of CRT in older women occurred following the ASTRO’s CW recommendation. Our study also highlights opportunities to enhance value-based radiation therapy use in BC.