Assessing the Impact of a Cooperative Group Trial on Breast Cancer Care in the Medicare Population

Abstract

Purpose The Cancer and Leukemia Group B (CALGB) C9343 trial found that adjuvant radiation therapy (RT) provided minimal benefits for older women with breast cancer. Although treatment guidelines were changed to indicate that some women could forego RT, the impact of the C9343 results on clinical practice is unclear. Patients and Methods We used the Surveillance, Epidemiology, and End Results (SEER) –Medicare data set to assess the use of adjuvant RT in a sample of women ≥ 70 years old diagnosed with stage I breast cancer from 2001 to 2007 who fulfilled the C9343 inclusion criteria. We used log-binomial regression to estimate the relation between publication of C9343 and use of RT in the full sample and across strata of patient and health system characteristics. Results Of the 12,925 Medicare beneficiaries in our sample (mean age, 77.7 years), 76.5% received RT. Approximately 79% of women received RT before study publication compared with 75% after (adjusted relative risk of receiving RT postpublication v prepublication: 0.97; 95% CI, 0.95 to 0.98). Although use of RT was lower after the trial within all strata of age and life expectancy, the magnitude of this decrease did not differ significantly by strata. For instance, among patients with life expectancy less than 5 years, RT use decreased by 3.7%, from 44.4% prepublication to 40.7% postpublication. Among patients with life expectancy ≥ 10 years, RT use decreased by 3.0%, from 92.0% to 89.0%. Conclusion The C9343 trial had minimal impact on the use of RT among older women in the Medicare population, even among the oldest women and those with shorter life expectancies.