Use of Medicare claims data to measure county-level variation in breast carcinoma incidence and mammography rates

Background: National-level population-based data about breast carcinoma incidence and its association with screening mammography are currently not available. Methods: Inpatient, hospital outpatient and physician/supplier Medicare claims were used to identify incident cases of breast carcinoma in women greater than or equal to65 years from 1996 to 1997 and calculate county-level incidence rates. The 1994-1995 claims data were used to determine county-level rates of mammography, and determine the correlation with incidence. Results: The median 2-year incidence rate for women greater than or equal to65 was 979/100,000, and substantial variation in incidence between counties was observed. (i.e. 25th percentile 789/100,000, 75th percentile 1186/100,000). Two-year county-level mammography rates also varied among counties (i.e. 25th percentile 30.5%, 75th percentile 40.9%) and were higher in white women than in black women (median 36.8 and 26.3%, respectively). Counties with higher rates of mammography also had higher age-adjusted incidence rates. Conclusions: Medicare claims may provide an alternative source of population-based data, particularly for areas in which registry data are not readily available, or are of limited scope. The data highlight the geographic variation in incidence and screening rates that may be useful for targeted interventions, and also suggest that mammography remains in a growth phase. (C) 2002 International Society for Preventive Oncology. Published by Elsevier Science Ltd. All rights reserved.