[Studies on the appropriated interval of mass screening for cervical cancer]

In order to study the appropriate interval for cervical cancer screening, we investigated mainly the screening history of 1,086 cervical squamous cancer cases detected by mass screening. 1) The cancer detection rate (CDR) for the 2-year successively screened group who were class I in the first screening was 0.051% and all cases were carcinoma in situ (CIS). In the 2-year interval screened group, detection rates for CIS, microinvasive cancer and stage 1b cancer were 0.053%, 0.035% and 0.018%. But there is no significant difference in CDR between the 2-year successively screened group and 2-year interval screened group (p less than 0.05). 2) In the 2-year successively screened group who were class II in the first screening, the CIS and microinvasive cancer detection rates were 0.044% and 0.022%. There is no significant difference in CDR between class I group and class II group. In the group who were class I in the first screening, we detected most cases in the stage 0 and a few cases in the stage Ia and Ib by mass screening at 2-year intervals. If the detection of a few cases in stage Ib is permitted, we can enforce mass screening for cervical squamous cancer at 2-year interval and it is considered that class II group can be screened at same interval as class I group.