Invasive carcinoma of the uterine cervix following diagnosis and treatment of in situ carcinoma. Record linkage study within a National Cancer Registry.

56117 women registered in the Swedish National Cancer Registry with the diagnosis carcinoma in situ of the uterine cervix were followed up and the risk for developing an invasive carcinoma of the uterine cervix was studied. The studied cohort provided 453 362 women years at risk. The primary treatment for carcinoma in situ in Sweden is generally conization. Hysterectomy is carried out in relatively few cases and intracavitary radium treatment was given to a limited number during the period studied. Cryosurgery and laser conization were of less quantitative importance during this period. The incidence rates of invasive carcinoma of the uterine cervix were compared with expected rates calculated from the National Cancer Registry. The ratio between observed and expected number of cases of invasive carcinomas of the uterine cervix is roughly 2.5 from the first year of observation after treatment of the in situ carcinoma until 20 years. There seems to be a distinct difference in risk for development of an invasive carcinoma of the uterine cervix for different age groups. In age group 50 years and older at time for treatment of the in situ lesion, 66 cases of invasive cancer were observed against 10.7 expected - O/E = 6.2. In ages 49 years or less, 145 cases were observed compared with 77.4 expected - O/E = 1.9. The conclusion from this study is that women treated for an in situ lesion are at a higher risk for an invasive carcinoma than the common female population and should be carefully followed up for a long time after treatment of the in situ lesion.