Rates and predictors of consideration for adjuvant radiotherapy among high-risk breast cancer patients: a cohort study.

Radiotherapy (RT) after breast conserving surgery (BCS) represents the standard for local control of breast cancer (BC). However, variations in practice persist. We aimed to characterize the rate of RT consideration (or referral) after BCS and identify predictors in Quebec, Canada, where universal health insurance is in place. A historical prospective cohort study using the provincial hospital discharge and medical services databases was conducted. All women with incident, non-metastatic BC (stages I-III) undergoing BCS (1998-2005) were identified. Odds ratios (ORs) and 95 % confidence intervals (CIs) for RT consideration were estimated with a generalized estimating equations regression model, adjusting for clustering of patients within physicians. Of the 27,483 women selected, 90 % were considered for RT and 84 % subsequently received it. Relative to women 50-69 years old, younger and older women were less likely to be considered: ORs of 0.82 (95 % CI 0.73-0.93) and 0.10 (0.09-0.12), respectively. Emergency room visits and hospitalizations unrelated to BC were associated with decreased odds of RT consideration: 0.85 (0.76-0.94) and 0.83 (0.71-0.97). Women with regional BC considered for chemotherapy were more likely to be considered for RT: 3.41 (2.83-4.11). RT consideration odds increased by 7 % (OR of 1.07, 95 % CI 1.03-1.10) for every ten additional BCSs performed by the surgeon in the prior year. Social isolation, comorbidities, and greater distance to a referral center lowered the odds. Demographic and clinical patient-related risk factors, health service use, gaps in other aspects of BC management, and surgeon's experience predicted RT consideration.