One of the most productive strategies health services researchers have used to assess the quality of cancer care has been to link cancer registry data to either administrative claims records or hospital discharge files. The data sources are often complementary—cancer registry data contain important information on diagnosis and cancer stage but may not record complete information on treatment that occurs outside the hospital. Administrative data may lack the diagnostic information but record a patient's treatment encounters. Linked data sets are not without problems. Administrative records may have treatments miscoded, comorbidity data needed to adjust results may be limited, and data elements necessary for complete linkage may be absent. Nevertheless, such linkages have allowed researchers to study variation in cancer care and to make comparisons across systems of care. A large study being conducted in California will provide information on the quality of registry treatment data, as well as maximize the potential of linkage using the cancer registry, hospital discharge data, and claims data from the Medicare program.

Many cancer registries are achieving nearly complete levels of case ascertainment, making them valuable as sampling frames for targeted special studies. Here, cancer registry staff may be asked to gather from medical charts clinical information to supplement that obtained for routine registry purposes. With appropriate resources, special studies can be launched relatively quickly in response to a specific research question. The SEER program has conducted a number of special studies, including a recent study of quality-of-life issues among men with prostate cancer following prostatectomy. The American Cancer Society is piloting two cancer survivorship surveys using state registries as sampling frames. Some state laws regarding confidentiality and consent have made timely access to research subjects difficult (e.g., requiring consent from the patient and the attending physician). Furthermore, Institutional Review Boards within hospitals can take several months to approve research projects.

The majority of privately insured Americans receive care within managed care organizations, but data on their care are often difficult to obtain because individual claims are usually not filed for each encounter. A number of plans have internal information systems and a population-based orientation to health care, making them ideal partners for research. The NCI has developed a consortium of such large managed care plans to collaborate on research.

Many of the federally sponsored national surveys can provide important descriptive information relevant to cancer, for example, use of health services and trends in service use. However, such surveys generally have limitations for cancer-related health services research because of the relatively rare occurrence of incident cases of disease and the lack of clinical detail on cancer (e.g., stage). Certain national data collection efforts, however, have great potential for cancer-related health services research. AHRQ's HCUP, for example, can be used to assess variations in patterns of care and differences in care across systems of care.

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