Do increases in the market share of managed care influence quality of cancer care in the fee-for-service sector?

BACKGROUND Increases in the market share of managed care in an area are associated with decreases in expenditures in the fee-for-service sector (i.e., a spillover effect). Given concerns that these decreases in expenditures result from reductions in necessary care, we examined associations between increases in managed care market share and changes in the quality of care delivered to cancer patients in the fee-for-service sector. METHODS We studied a population-based sample of fee-for-service Medicare beneficiaries aged 66 years or older who were diagnosed with breast (N = 41,394) or colorectal (N = 48,027) cancer during 1993-1999. We used fixed effects regression analysis of SEER cancer registry and Medicare claims data to assess whether county-level increases in the market share of managed care over time were associated with the quality of cancer care. All statistical tests were two-sided. RESULTS Increases in the market share of managed care were not associated with most quality indicators, including receipt of surveillance mammography after diagnosis for patients with breast cancer (P = .83), receipt of radiation after breast-conserving surgery among women who underwent breast-conserving surgery (P = .16), receipt of adjuvant chemotherapy for patients with stage III colorectal cancer (P = .94), or surveillance colonoscopy after treatment for colorectal cancer (P = .39). Increases in the market share of managed care were associated with increased rates of surveillance carcinoembryonic antigen testing for colorectal cancer patients (P = .001). CONCLUSIONS Increases in managed care market share had limited or no effect on the quality of care for cancer patients. Concerns that increases in managed care would have large negative spillover effects on the quality of cancer care appear to be unfounded; however, the potential for managed care to stimulate improved quality throughout the medical care system have not yet been realized.