Cervical cancer detection in British Columbia: a progress report.

The cervical cancer detection program started in British Columbia in 1949 was reviewed to determine the merits of cytology as a screening procedure for early detection and control of cervical cancer. Data from 1958-66 was utilized because of its availability for machine analysis. The program detected 3667 cases of preclinical squamous carcinoma. Incidence rates were calculated from cases that were known to have been previously negative (both clinically and cytologically); denominator used was person-years of negative cytological experience. Results indicate that the disease begins most commonly in the 25-29 age group but is most prevalent in the 35-39 age group. A steady decline in the incidence of clinical invasive carcinoma was observed since 1955. Another perhaps more effective way of evaluating a screening program is comparing the annual incidence of invasive diseases in the screened segment of the population with the rate in the unscreened population; the socioeconomic and age differentials of the 2 groups must be considered however when using this method. Because cytology is not a perfect diagnostic procedure and has at least 10% false negative error statistical calculation of incidence and prevalence rates predicated on uncertain conditions should be carefully evaluated. This study confirms the report that removal of in situ carcinoma a precursor of invasive carcinoma results in a significant reduction of morbidity and mortality from cervical carcinoma.