A model-based comparison of breast cancer screening strategies: mammograms and clinical breast examinations.

In screening for secondary prevention of breast cancer, clinical breast examination (CBE) combined with mammography may improve overall screening sensitivity compared with mammography alone. A systematic evaluation of the relative expenses and projected benefit of combining these two screening modalities is not presently available. We addressed this issue using a microsimulation model incorporating age-specific preclinical duration of the disease, age-specific sensitivities of the two modalities, age-specific incidence of the disease, screening strategy, and competing causes of mortality. We examined a total of 48 screening strategies, depending on the age range, the examination interval, and whether mammography or CBE is given at every one or two exam. Our results indicate that a biennial mammography can be cost-effective if coupled with annual CBE. For each screening interval and starting age, giving mammography every two exams and CBE at every exam has the lowest marginal cost per year of quality-adjusted life saved, whereas giving both at every exam has the highest. Comparing annual mammography and CBE to biennial mammography and annual CBE from 50 to 79, the total cost was reduced by 35%, whereas the marginal quality-adjusted life years only decreased by 12%. Similar reductions are observed for other starting ages. It is cost-effective to have a biennial mammography if coupled with an annual CBE. Annual mammography combined with CBE every 6 months will lead to a 41% increase in the quality-adjusted life years compared with annual mammography and CBE from 50 to 79, whereas the total cost increases by 30%.