Projecting mammographic screens

Objective-The purpose of mammographic screening is to reduce mortality from breast cancer. This study describes a method for projecting the number of screens to be performed by a mammographic screening programme, and applies this method in the context of New South Wales, Australia. Method-The total number of mammographic screens was projected as the sum of initial screens and re-screens, and is based on projections of the populat ion, rates of new recruitment, rates of attrition within the programme, and the mix of screening intervals. The baseline scenario involved: 70% partic ipation of women aged 50-69 years, 90% return rate for the second and subse quent re-screens, 5% annual screens (95% biennial screens), and a specified population projection. The results were assessed with respect to variation s in these assumptions. Results-The projections were strongly influenced by: the rate of screening of the target age group; the proportion of women re-screened annually; and the rates of attrition within the programme. Although demographic change ha d a notable effect, there was little difference between different populatio n projections. Standard assumptions about attrition within the programme su ggest that the current target participation rates in NSW may not be achieve d in the long term. Conclusions-A practical model for projecting mammographic screens for popul ations is described which is capable of forecasting the number of screens u nder different scenarios. Implications-Projections of mammographic screens provide important informat ion for the planning and financing of equipment and personnel, and for test ing the effects of variations in important operational parameters. Re-scree ning attrition is an important contributor to screening viability.