FFS care with care in a staff-or group-model HMO. These studies show processes and outcomes of care in these settings that are equal to or better than those in FFS settings.
The findings of many of the studies of managed care can be challenged on methodological grounds—retrospective cross-sectional designs, small sample sizes, nonrandom potentially biased selection of cases, and inadequate use of control variables to adjust for underlying differences in patient populations served in HMOs and FFS. Furthermore, most of the studies have been limited to large staff-or group-model HMOs that now represent only about 15 percent of managed care enrollment (http://www.aahp.org). Five of the eight studies reviewed evaluated the care of patients diagnosed before 1990. Most of these studies included an analysis of mortality, so long follow-up times were necessary; however, the processes of care that may have contributed to differences in outcomes have in all likelihood changed. Recent evidence points to significant variation among HMOs in the quality of cancer treatment (Riley et al., 1999). Carefully designed, large studies are needed to assess how features of managed care plans and market areas affect the quality of cancer care.
Among the first questions many individuals ask after receiving a diagnosis of cancer care are, ''Where should I go for care?'' and "What kind of doctor should I see?" Health services research has not fully addressed these important questions. There is very limited evidence on the way structures and technical processes of care affect cancer care outcomes, and the strength of available evidence is weakened by methodological shortcomings of the research. Only a handful of studies were available for this review on the effects of managed care or on the effects of the volume and specialization of facilities or physicians on cancer care quality. Many of the available studies on these topics were done outside the United States, making inferences to care in the United States difficult. Most of the published literature includes mortality as the main outcome measure and has long periods of follow-up. Consequently, most of the studies apply to patients who were diagnosed with cancer in the early to late 1980s.
A large body of evidence supports a relationship between high surgical case volume and better survival for several cancers for which high-risk surgery is indicated (e.g., pancreatic cancer, non-small-cell lung cancer). Several studies show very large effects, with low-volume hospitals having postsurgical mortality rates two to three times those of high-volume hospitals. A dose-response effect is also evident to support the finding that as volume increases, so do good outcomes. The observational studies described, however, must be interpreted cautiously because they are prone to biases that favor large centers (e.g., greater use of diagnostic tests can contribute to a stage migration bias; patients at high-volume centers tend to be healthier than at smaller hospitals).
Studying the effect of institutional specialization on outcomes is difficult because specialization is often closely tied to the size of a facility and the volume of services. Nevertheless, a number of studies have attempted to identify differences in outcomes of facilities according to various measures of specialization—for example, whether they are cancer centers, university affiliated, or designated as research centers or have residency training programs. There does appear to be a consistent trend of improved outcomes associated with specialization, however defined.