SURVIVAL TREND AFTER INVASIVE CERVICAL-CANCER DIAGNOSIS IN SWEDEN BEFORE AND AFTER CYTOLOGIC SCREENING - 1960-1984

Background. Cytologic screening can reduce mortality from cervical can cer by detection and removal of premalignant lesions. Conceivably, mor tality is further reduced because more women with invasive disease are diagnosed at an earlier, curable stage. This hypothesis can be assess ed in Sweden, where population-based screening programs were introduce d successively over about a decade starting in 1964. Methods. Record l inkages permitted complete follow-up through 1986 of all 17,377 patien ts with invasive cervical cancer diagnosed in Sweden from 1960 through 1984. We analyzed relative survival rates that describe the survival of patients after elimination of the effects of causes of death other than cancer of the cervix. Results. Prognosis improved substantially i n patients younger than age 50 years at diagnosis; from 1960-1964 to 1 980-1984, the 5-year relative survival rate increased from 69.8% to 88 .8% at age 20-29 years, from 71.7% to 85.5% at age 30-39 years, and fr om 68.6% to 77.9% at age 40-49 years. The excess mortality was thus re duced by more than half in patients diagnosed when younger than 40 yea rs. In contrast, only slight or no improvement was noted in those diag nosed at older ages when screening was less extensive. In all time per iods, a strong association was found between older age at diagnosis an d poorer prognosis. Conclusion. Although alternative explanations for our findings must be seriously considered, the most obvious interpreta tion is that cytologic screening reduces mortality from cervical cance r by earlier diagnosis of invasive disease.