Screening for cancer of the cervix uteri.

Cervical cancer is the second most common cancer in women worldwide. The majority of cervical cancers are squamous cell carcinomas. Pap smears for early detection of precursor lesions of cervical cancer have been available for 40 years. A clinical trial to evaluate Pap smears was never undertaken; however, evidence gradually accumulated from time trend analyses and from cohort and case-control studies showed the incidence and mortality of cervical cancer to be reduced by organized screening programs. The risk of cervical cancer following different screening histories was estimated in a recent study of the International Agency for Research on Cancer. Screening with 1-year and 3-year intervals was estimated to reduce the incidence of squamous cervical cancer by 94% and 91%, respectively. Cervical cancer is rare in young women, and little was estimated to be gained from including women below the age of 25 years in organized screening programs. The age distribution of cervical cancer has changed; a substantial proportion of cases now occur in the older generations of women, who have never been offered organized screening. Computerized pathology registration systems may serve as a tool for integration of the total smear-taking activity and, thus, ensure that a high percentage of women are screened regularly at minimized costs. The planning of a screening program should include both the smear-taking activity and the treatment.