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Table 2 Estimates of geographic access to chemotherapy by provider and service location definitions

From: Variation in geographic access to chemotherapy by definitions of providers and service locations: a population-based observational study

Access to Chemotherapy Measure

Provider Identification Method

Proven Service locations

Possible Service locations

Mean (SD)


Mean (SD)


Number of chemotherapy providers within 20 minutes of beneficiary ZIP

Oncology Specialty Codes

21.1 (29.8)


21.3 (30.0)


Chemotherapy Billing Codes

41.9 (52.3)


46.3 (57.3)


Driving-time distance to nearest chemotherapy provider (minutes)

Oncology Specialty Codes

16.1 (20.3)


15.9 (20.1)


Chemotherapy Billing Codes

12.2 (16.6)


11.2 (15.9)


  1. Data are from SEER-Medicare. Sample included all patients diagnosed with lung cancer that were reported to the SEER registries in 2006. Chemotherapy providers were identified in one of two ways: by specialty codes reported on Carrier claims (83 for Hematology/Oncology and 90 for Medical Oncology), and by chemotherapy-related billing codes on Carrier claims (Table 1). Chemotherapy service locations were identified in one of two ways: proven service locations are locations from where providers billed a chemotherapy-related service, and possible service locations are all locations in which the providers practice. Two geographic access to care measures are estimated: local area density (the number of chemotherapy providers within 20-minutes driving time of beneficiary ZIP code), and driving-time distance in minutes between the beneficiary ZIP code centroid and the centroid of the ZIP code of the nearest provider. These measures do not make any assumptions about whether beneficiaries received chemotherapy or from whom, and are instead a measure of potential access to care