Practice Consolidation Among U.S. Radiation Oncologists Over Time

Abstract

Healthcare practices across the U.S. have been consolidating in response to various market forces. The degree of practice consolidation varies widely across different specialties, but has not been well studied within radiation oncology. Our study used Medicare data to characterize the extent of practice consolidation among radiation oncologists, and to investigate the associated market factors influencing this phenomenon.We utilized Medicare Provider Enrollment, Chain, and Ownership System data to assess the practice size and billing patterns of radiation oncologists in the U.S. between 2013 and 2017. Individual practices were identified via unique Taxpayer Identification Numbers (TIN). Practices were classified by the number of radiation oncologists billing under their TIN as either solo (1 radiation oncologist), small (2 to 10), or large practices (11 or more). Hospital and market level data were obtained for each hospital referral region (HRR) across the country, and factors associated with the growth of radiation oncology practices over time were assessed via multivariable linear regression. Market consolidation within each HRR was quantified using the Herfindahl-Hirschman Index (HHI). This metric sums each practice's squared market share and ranges from 0 to 1. Notably, the U.S. government defines markets with an HHI above 0.25 to be "highly concentrated".Between 2013 and 2017, the number of practices with radiation oncologists in the U.S. decreased from 1,697 to 1,615, while the number of practicing radiation oncologists increased from 4,948 to 5,415. Consequently, the mean radiation oncology HHI increased from 0.4711 to 0.4865. Over the study period, the number of solo practices fell 11% (from 708 in 2013 to 627 in 2017), while the number of large practices increased 50% (from 60 to 90). Large practices likewise grew to employ a larger share of all radiation oncologists (23.9% to 32.4%), and accounted for a greater proportion of total Medicare billing (21% to 26%). Two market factors were predictive for increases in the mean radiation oncology practice size. HRRs with greater hospital market consolidation and those with lower levels of baseline radiation oncology consolidation were more likely to experience higher levels of growth over the study period.Radiation oncologists are increasingly working in larger practices. By 2017, nearly one-third of all practicing radiation oncologists in the U.S. were employed by just the 90 largest practices. Radiation oncology, as a field, is highly concentrated, and represents one of the most consolidated specialties across the country. A growing body of literature has shown that greater levels of practice consolidation are associated with higher costs with little apparent improvement in quality. However, specific studies on the impacts of practice consolidation in radiation oncology are needed.