Variations in treatment for ductal carcinoma in situ in elderly women.

OBJECTIVE: The objective of this study is to quantify variation and variability in treatment of ductal carcinoma in situ (DCIS) over time and across registries of the Surveillance, Epidemiology, and End Results (SEER) program; to assess diffusion of treatments (breast-conserving surgery [BCS], BCS with radiotherapy, and mastectomy); and to identify correlates of treatment choice. DATA: The linked SEER-Medicare database from 1991 to 1996 includes 2701 women aged 65 and older diagnosed with unilateral DCIS. 1990 census data provide socioeconomic variables at the zip-code level, and the 1999 Dartmouth Atlas of Health Care provides number of radiation oncologists. STUDY
DESIGN: Bivariate and multivariate analyses of retrospective cohort data assess factors that explain treatment choice. The multivariate model includes controls for comorbidity, marital status, age, race, education, poverty, rural, and radiation oncologists per 100,000 population. Chi-squared tests assess differences in treatment rates by registry and by year. Diffusion of treatments is analyzed by predicting yearly mean treatment rates and yearly variation in treatment rates across geographic areas and over time.
RESULTS: There are significant geographic and temporal differences in treatment rates for DCIS with increasing use of BCS alone. Treatment choice is explained by SEER registry, diagnosis year, marital status, race, age, urban/rural status, educational attainment, and number of radiation oncologists. Variability in treatment of DCIS is increasing during the study period.
CONCLUSIONS: Findings indicate that diagnosis year and socioeconomic factors explain treatment choice for DCIS, but unexplained variation at the geographic-region level remains. Increasing variability in treatment implies continued uncertainty about optimal treatment of DCIS.