Diffusion of accelerated partial breast radiotherapy in the United States: physician-level and patient-level analyses.

Abstract

To evaluate diffusion of brachytherapy-based accelerated partial breast radiotherapy (RT) in the United States, a new breast cancer treatment requiring 5 days twice daily, rather than daily treatment for 6-7 weeks. It has limited long-term effectiveness data compared with standard whole breast RT. We used 2005-2008 Medicare claims for female Medicare beneficiaries receiving RT after breast-conserving surgery merged with physician and area-based data (n=74,254 patient-subjects; n=1901 physicians), applying logistic regression to estimate: (1) proportion of patients for whom the radiation oncologist used brachytherapy-based accelerated RT, and (2) probability a patient received brachytherapy-based accelerated RT, clustering on physician. Use of accelerated partial breast RT increased over time (8% in 2005 to 17% in 2008). Physician-level analysis indicates rural physicians were less likely to perform accelerated RT [odds ratio (OR): 0.35-0.49; P<0.002)]; as were those licensed 20+years [OR: 0.54; 95% confidence interval (CI), 0.39-0.74]. Overall, 11.7% of patients received accelerated RT. Treatment post 2005 was associated with increasing odds of receiving accelerated RT (P<0.0001). Older age was associated with lower odds of receiving accelerated RT (reference, 66-69 years old, OR: 0.90, P<0.006), as was black (OR: 0.73;95% CI, 0.63-0.85) or other race (OR: 0.80; 95% CI, 0.65-1.00), living in rural areas (OR: 0.8; P<0.0001), or seeing an older physician [20+years postgraduation (OR: 0.7; 95% CI, 0.5-0.9)]. Patients living in counties with more hospitals with advanced RT facilities were more likely to undergo accelerated RT (OR: 1.4; 95% CI, 1.1-1.8). This new technology appears to be in the early phase of diffusion across the United States and is more rapidly being taken up in younger, white patients living in urban and suburban areas with availability of advanced RT facilities. Rural and older patient populations are not tending to undergo the treatment.