Adjuvant radiotherapy use in a population-based sample of breast cancer patients
617 Background: Previous studies have suggested underutilization and socioeconomic disparities in use of adjuvant radiotherapy (RT) among patients with breast cancer. However, these studies used registry data which may be incomplete. Methods: We evaluated data from 2260 survey respondents with nonmetastatic breast cancer, aged 20–79 years, diagnosed from June 2005-February 2007 in Detroit and Los Angeles and reported to SEER registries (72% response rate). Survey responses regarding treatment and sociodemographic factors were merged to SEER data. Rates of RT receipt were based on patient report. Patients were divided into 3 populations: DCIS pts undergoing breast conservation (BCS), invasive pts undergoing BCS, and invasive pts undergoing mastectomy. These were then stratified based on recurrence risk in the absence of RT (3 groups based on tumor size and grade for DCIS pts, 2 groups separating pts over 70 with Stage I, ER+ tumors from others undergoing BCS for invasive disease, and 3 groups based on tumor size and nodal status for those undergoing mastectomy for invasive disease). Results: Among 306 pts undergoing BCS for DCIS, 85.6% received RT (77.9% of pts at low recurrence risk, 84.8% at intermediate risk, and 95.8% at high risk). Among 1018 pts undergoing BCS for invasive disease, 93.6% received RT (83.6% of low-risk patients and 94.9% of others). Among 661 pts undergoing mastectomy for invasive disease, 39.3% received RT (81.5% of pts at high-risk, 44.5% at intermediate-risk, and 12.1% at low risk). In separate multivariate logistic regression models including risk grouping and sociodemographic variables for each population, there were no significant associations between RT receipt and race, education, or income. Among pts receiving RT, delay was reported by 15.9% of the DCIS group, 19.5% of those treated for invasive disease after BCS, and 27.4% of those treated for invasive disease after mastectomy. Conclusions: RT use is high after BCS with little evidence of socioeconomic disparities. But lower than optimal rates after mastectomy even among patients with high expected benefit suggest lingering barriers to effective treatment in these patients. Less RT use in patients with lower expected benefit suggests that legitimate clinical uncertainty influences decision-making. No significant financial relationships to disclose.