Long-term Impact of CALGB 9343 on Radiation Utilization.

backgroundThe results of the Cancer and Leukemia Group B (CALGB) 9343 trial showed that radiation therapy (RT) did not improve survival for women older than 70 y with early-stage estrogen receptor + breast cancer treated with breast conserving surgery and adjuvant endocrine therapy. In 2005, guidelines were modified to allow for RT omission; however, minimal change in clinical practice has occurred. The aim of this study was to determine if CALGB long-term follow-up data have affected RT utilization, and to characterize the population still receiving RT after breast conserving surgery.

methodsThe Surveillance, Epidemiology, and End Results-Medicare database was used to identify women diagnosed with early-stage breast cancer from 2004 to 2015 who matched the CALGB 9343 inclusion criteria. Multivariate logistic regression was carried out to identify the factors that affect the receipt of radiation therapy. We also plotted the overall use of RT over time juxtaposed with the temporal trends of CALGB 9343 clinical trial data, guideline recommendations, and publishing of long-term survival data.

resultsThe study cohort included 25,723 Medicare beneficiaries, of whom 20,328 (79%) received RT and 5395 (21%) did not receive RT. In a multivariate model, the frequency of RT omission increased over time, with those diagnosed in year 2015 being 2.72 times more likely to omit RT compared with those diagnosed in 2004 (95% confidence interval 2.31-3.19).

conclusionsThis study investigated the impact of long-term CALGB 9343 data on clinical practice. The results of this study support results from previous studies, extend the dates of analysis, and indicate that after long-term follow-up of CALGB 9343 data, RT was less used, but overall trends did not dramatically decrease.