Finding incident breast cancer cases through US claims data and a state cancer registry

Objective: With the increasing availability of automated health-care data, new methods are available to screen large populations for the presence of cancer diagnoses. However, it is crucial to evaluate how completely incident cancer cases can be ascertained using these data sources. Methods: We used capture-recapture techniques to estimate the total number of incident breast cancer cases occurring within one state during a 3-year period. We then compared the ascertainment of these cases by the following two data sources: claims for breast cancer surgery recorded in Medicaid and Medicare data vs a cancer registry in the same state. Results: Medicaid-Medicare breast cancer surgery claims identified 68% of the total estimated number of incident breast cancer cases while cancer registry data identified 78%. Case ascertainment improved markedly to 91% when both registry and Medicare-Medicaid data sources were used together. The sensitivity of ascertainment was lower for Medicaid-Medicare data among those aged under 65 and non-white; ascertainment was lower for the registry among women who were aged under 65, poor, and non-white. Conclusions: Combining health insurance claims data with a population-based cancer registry improved the identification of incident cases of breast cancer, and may be particularly useful among demographic groups found to be at highest risk of under-ascertainment such as younger women, the poor, and racial minorities.