Follow-up after screening for colorectal neoplasms with fecal occult blood testing in a controlled trial

Abstract

PURPOSE: The aim of this study was to investigate the number of new colorectal neoplasms during the first seven years after the end of rescreening in a prospective randomized screening study. METHODS: 27,700 inhabitants of Göteborg born between 1918 and 1922 (60-64 years old) who were randomly allocated to a control or a test group in 1982 were followed up. All people in the latter group were offered six fecal occult blood tests and rescreening 16 to 22 months later. RESULTS: One hundred one carcinomas were diagnosed in the screened group and 128 in the control group during the seven years of follow-up. The number of carcinomas in the test group was half that in the control group during the first two years of follow-up, but equal during the rest of the follow-up period. The distribution of carcinomas according to Dukes classification was significantly better among the participants compared with the refusers (P < 0.02) but there was no difference in the Dukes distribution when the test and control groups as a whole were compared. The number of adenomas in the two groups during seven years of follow-up was the same. CONCLUSION: The results indicate that screening and rescreening of a population has little influence upon the stage of the carcinomas in the test group compared with a control group during the first seven years of follow-up. The number of carcinomas was higher in the control than in the test group during the follow-up, probably because of a lead time effect during the screening.