title: Variation in geographic access to chemotherapy by definitions of providers and service locations: a population-based observational study.
abstract: An aging population, with its associated rise in cancer incidence and strain on the oncology workforce, will continue to motivate patients, healthcare providers and policy makers to better understand the existing and growing challenges of access to chemotherapy. Administrative data, and SEER-Medicare data in particular, have been used to assess patterns of healthcare utilization because of its rich information regarding patients, their treatments, and their providers. To create measures of geographic access to chemotherapy, patients and oncologists must first be identified. Others have noted that identifying chemotherapy providers from Medicare claims is not always straightforward, as providers may report multiple or incorrect specialties and/or practice in multiple locations. Although previous studies have found that specialty codes alone fail to identify all oncologists, none have assessed whether various methods of identifying chemotherapy providers and their locations affect estimates of geographic access to care.
  
  
  
  SEER-Medicare data was used to identify patients, physicians, and chemotherapy use in this population-based observational study. We compared two measures of geographic access to chemotherapy, local area density and distance to nearest provider, across two definitions of chemotherapy provider (identified by specialty codes or billing codes) and two definitions of chemotherapy service location (where chemotherapy services were proven to be or possibly available) using descriptive statistics. Access measures were mapped for three representative registries.
  
  
  
  In our sample, 57.2 % of physicians who submitted chemotherapy claims reported a specialty of hematology/oncology or medical oncology. These physicians were associated with 91.0 % of the chemotherapy claims. When providers were identified through billing codes instead of specialty codes, an additional 50.0 % of beneficiaries (from 23.8 % to 35.7 %) resided in the same ZIP code as a chemotherapy provider. Beneficiaries were also 1.3 times closer to a provider, in terms of driving time. Our access measures did not differ significantly across definitions of service location.
  
  
  
  Measures of geographic access to care were sensitive to definitions of chemotherapy providers; far more providers were identified through billing codes than specialty codes. They were not sensitive to definitions of service locations, as providers, regardless of how they are identified, generally provided chemotherapy at each of their practice locations.
authors.affiliation: Department of Pharmacy Practice and Science, College of Pharmacy, University of Iowa, 115 South Grand Ave, S525 PHAR, Iowa City, IA, 52242, USA. mary-schroeder@uiowa.edu.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Schroeder
authors.affiliation: Department of Health Services Policy and Management, Arnold School of Public Health, University of South Carolina, Columbia, SC, 29208, USA.
authors.forename: Cole G
authors.initials: CG
authors.lastname: Chapman
authors.affiliation: Department of Health Management and Policy, College of Public Health, University of Iowa, Iowa City, IA, 52242, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Nattinger
authors.affiliation: Department of Oncology (Medical), Mayo Clinic, Rochester, MN, 55905, USA.
authors.forename: Thorvardur R
authors.initials: TR
authors.lastname: Halfdanarson
authors.affiliation: Division of Hematology, Oncology and Blood and Marrow Transplantation, Department of Internal Medicine, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.
authors.forename: Taher
authors.initials: T
authors.lastname: Abu-Hejleh
authors.affiliation: Program in Pharmaceutical Socioeconomics, Department of Pharmacy Practice and Science, College of Pharmacy, University of Iowa, Iowa City, IA, 52242, USA.
authors.forename: Yu-Yu
authors.initials: YY
authors.lastname: Tien
authors.affiliation: Department of Health Services Policy and Management, Arnold School of Public Health, University of South Carolina, Columbia, SC, 29208, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Brooks
mesh_terms: D016208:Databases, Factual; D006297:Health Services Accessibility; D006801:Humans; D008495:Medical Oncology; D009369:Neoplasms / Q000188:drug therapy*; D011365:Professional Practice Location; D018426:SEER Program; D014481:United States
keywords: Cancer; Chemotherapy; Geographic access to care; Oncologists