Background: Hospital tumor registries, which provide data that inform health services research and cancer control policies, may be a source of information about quality of cancer care. However, the accuracy of data from such registries is unknown.
Objective: To determine the accuracy of tumor registry data by comparing it with data collected from numerous sources for a breast cancer quality improvement project.
Design: Retrospective cohort study.
Setting: Three teaching hospitals with tumor registries in the New York metropolitan area that had participated in the quality improvement project.
Patients: All women with newly diagnosed primary breast cancer (stage I or stage II) who were surgically treated at the study hospitals between 1 November 1994 and 31 August 1996.
Measurements: Sensitivity and specificity were calculated, and data from the quality improvement project were used as the gold standard.
Results: The tumor registries and the quality improvement project had similar information on tumor stage and surgery type. Sensitivity ranged from 0.91 to 0.96, and specificity ranged from 0.93 to 0.97. When both sources were used to calculate quality measures, the overall rate of radiation therapy after breast-conserving surgery was 80% in the quality improvement project and 48% in the tumor registries (sensitivity, 0.58; specificity, 0.94). For receipt of adjuvant systemic treatment, the rate was 78% in the quality improvement project and 22% in the tumor registries (sensitivity, 0.27; specificity, 0.97).
Conclusions: Data from tumor registries provide accurate measures for hospital-based surgical treatments but not for outpatient treatments. Unverified tumor registry data should not be used to measure quality of care.