Breast cancer outcomes among older women: HMO, fee-for-service, and delivery system comparisons

Research into the effectiveness of HMOs among Medicare patients aged 65 or more is important since the number of Medicare beneficiaries enrolled in HMOs has grown from 3.6 million in 1995 to 5.6 million in 1997,1,2 and leading Medicare reform proposals would expand the use of managed care. Although managed care potentially can improve health care quality by facilitating prevention, screening and treatment interventions, recently there has been growing concern about quality of care provided by HMOs. Breast cancer is a significant disease, for which data are available to research the performance of HMOs among Medicare patients. Among U.S. women aged 65 or more, breast cancer is the most common site of new invasive cancers and the second most common cause of cancer mortality, with an estimated 87,500 new cases and 26,000 deaths in 1996.3,4 Further, early detection and treatment of breast is associated with improved survival. In California (current study site) breast cancer mortality among older women fell about 9% from 1988 to 1996,5 owing in part to increased use of screening mammography and earlier stage at diagnosis.6–8 Major clinical trials in the 1980s demonstrated that survival was similar for early stage breast cancer patients treated with breast-conserving surgery (BCS) or mastectomy.9–11 Subsequently the 1990 NIH Consensus Conference12 recommended BCS plus radiation therapy as preferable treatment for the majority of Stage I or II breast cancers without reference to age of the patient. The proportion of early stage breast cancers treated with BCS among older California women increased from 28% in 1988 to 43% in 1992.7 The present multivariate study of breast cancer patients aged 65 and older residing in northern California investigates quality of breast cancer care by examining the relationship of six types of health insurance to three outcomes: 1) stage at diagnosis; 2) treatment modality selected; and 3) survival. The study also considers breast cancer outcomes relative to hospital type while adjusting for other factors known to be associated with these outcomes (age, ethnicity, education, neighborhood class, and time period).13–23 This paper explores the following hypotheses: 1) Among Medicare beneficiaries with breast cancer, the odds of early stage diagnosis differ between those with private insurance (private FFS, group-model HMO, non-group-model HMO) and those without, and within the private insurance group stage at diagnosis varies by insurance type; 2) Among Medicare patients diagnosed at an early stage, use of BCS plus radiation varies over time and with hospital type; and 3) Among Medicare beneficiaries having early stage breast cancer, there are insurance-related differences in survival, with better outcomes associated with private insurance. In testing these hypotheses the current study extends and improves upon existing literature in several ways. First, few prior studies of breast cancer stage at diagnosis among Medicare beneficiaries compared HMO and FFS patients, and none employed the detailed categorization of insurance coverage found here.15,18,23,24 In an earlier study, Riley et al.18 used a heterogeneous FFS group, including Medicare patients with private FFS supplemental insurance as well as those having only Medicare and those with Medicaid; but this FFS grouping biases inferences related to detection and treatment in favor of HMOs. In addition, the current study distinguishes between group and non-group model HMOs, which is important since they differ in physician culture, organization, and financial incentives. While much early research involving HMO treatment outcomes among older females is based on data from group model plans, growth in HMO enrollment in the 1980s and 1990s was almost entirely due to non-group model plans.25 Two previous investigators22,23 considered the relationship between insurance coverage and breast cancer treatment among Medicare patients (again, using the catch-all FFS category), lacking controls for hospital type. Conversely, many others considered the relationship between hospital characteristics and breast cancer treatment for women aged 65 or more, without accounting for differences in insurance coverage among patients.17,19–21,26–29 The present study improves upon most of this literature by including both insurance and hospital type, using a hospital typology which includes a category for HMO-owned hospitals. A final advantage of this study relative to earlier research is the time period (1987–1993) to which the current data pertain, providing new HMO/private FFS comparisons regarding diagnosis and survival among older women. The timing of the present study is also well-suited for studying breast cancer outcomes, as diagnosis of study subjects encompasses both the NIH Consensus Conference year and inception of Medicare coverage for biennial mammograms (1990).