Practice Consolidation Among U.S. Radiation Oncologists Over Time

Health care practices across the United States have been consolidating in response to various market forces. The degree of practice consolidation varies widely across specialties but has not been well studied within radiation oncology. This study used Medicare data to characterize the extent of practice consolidation among radiation oncologists and to investigate associated market factors.

We utilized Medicare Provider Enrollment, Chain, and Ownership System data to assess the practice size and billing patterns of U.S. radiation oncologists in 2013 and again in 2017. Individual practices were categorized by the number of radiation oncologists practicing together: solo practices had 1 radiation oncologist, small practices 2 to 10, and large practices 11 or more. Market consolidation within each hospital referral region (HRR) across the country was quantified using the Herfindahl-Hirschman Index. Hospital and market level data were obtained for each HRR, and factors associated with the growth of radiation oncology practices over time were calculated via multivariable linear regression.

Across the United States, radiation oncology practices appear to be highly consolidated. The mean Herfindahl-Hirschman Index was 0.4711 in 2013-indicating high levels of consolidation at baseline-and increased further to 0.4865 by 2017. Between 2013 and 2017, the number of practices with radiation oncologists in the United States decreased 3.8%, from 1679 to 1615, whereas the number of practicing radiation oncologists increased 9.4%, from 4948 to 5415. Over the study period, the number of solo practices fell 11% (from 708 in 2013 to 627 in 2017), whereas the number of large practices (those with 11 or more radiation oncologists) increased 50% (from 60 to 90). Large practices likewise grew to employ a greater share of all radiation oncologists (23.9%-32.4%) and accounted for a larger proportion of total Medicare billing (21%-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 United States 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. The implications of practice consolidation among radiation oncologists warrants further investigation.