Preventive Pap-smears: balancing costs, risks and benefits

Abstract

Summary The pattern of spontaneous screening for cervical cancer by general practitioners and gynaecologists in The Netherlands is compared with an efficient screening policy resulting from a cost-effective study. Spontaneous screening tends to start and stop too early in a woman's life, and leaves too many women overscreened or unprotected. The combination in young age of a low incidence of invasive cancer and a high incidence of regressive lesions explains relative ineffectiveness and harmfulness of present screening practice. When screening would take place between ages 30 and at least 60, with intervals of about 5 years, as many lives could be saved for half the costs and with only 60% of the unnecessary referrals and treatments. Much attention should be paid to the coverage of the target population. Therapeutic follow-up policies for dysplastic lesions should be restrained.Screening has contributed to the decrease in cervical cancer mortality in several countries (Day 1986a, Hakama, 1985Laara et al., 1987;Day, 1984;van der Graaf et al., 1988). There is still debate on the age to start screening and on the interval. Some screening recommendations call for intensive screening at a young age (ACOG, 1980; CTF, 1982) but studies which analyse the health effects of screening conclude that screening efforts should be directed to middle aged and older women (Liiara et al., 1987;Knox, 1976;Miller, 1985;Day, 1986b;Parkin et al., 1986). The advocated interval has been lengthening the last few years but in practice the interval tends to be still short.The pros and cons of screening policies critically depend on the duration and detectability of the preclinical stages of the disease. Knowledge of these important parameters can be derived from the results of existing screening programmes. Therefore, a detailed analysis was made of data from the early detection programmes in British Columbia and in The Netherlands. Both analyses led to very similar conclusions (Habbema et al., 1985). The first one has been published recently in this journal (van Oortmarssen, 1991).In this article we study the consequences of the results on duration and regression for balanced Pap-smear taking. We compare spontaneous screening with optimised screening, studying the costs, risks and benefits. Methods and materialsThe natural history For The Netherlands, the following estimates were derived: -a smear will detect 70% of the cases of cervical intraepithelial neoplasia (CIN) III (sensitivity, that pertains to the situation in which women with at least (cytologically) moderate dysplasia twice or severe dysplasia once are referred for colposcopy); -0.4% of the smears will be false-positive (no CIN, or at the most CIN II will be found histologically).the mean duration of CIN III is 15 years; -on average 60% of the cases of CIN III will regress spontaneously, this percentage is highest at younger age (see Figure 1); -a higher incidence of cervical cancer in non-attenders to screening than in attenders. Predictive calculationsThe assumptions on nat...

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