[Reducing incidence and mortality from rectal cancer by polypectomy: a prospective cohort study]

To address the hypothesis that colorectal cancers often arise from precursor lesion(s), either adenomas or non-adenomatous polyps.

A population-based mass screening for rectal cancer using 15cm rigid endoscopy was conducted in Haining County, Zhejiang province, from 1977 to 1980. Of over 230,000 participants, 4,076 of them were diagnosed with precursor lesions, either adenomas or non-adenomatous polyps, which were then removed. All individuals with precursor lesions were followed and re-examined by endoscopy every two to five years through 1998.

After the initial screening, 952 metachronous adenomas and 417 non-adenomatous polyps were detected and removed from the cohort. Furthermore, 27 cases of colorectal cancer were detected and treated. Log-rank tests showed that the years of survival significantly increased among those cancer patients who had undergone mass screening compared to other rectal cancer patients (P < 0.001). According to the population-based cancer registry in Haining County, both age-adjusted incidence and mortality rates from rectal cancer decreased from 1977 to 1996. Observed accumulative incidence and mortality rates decreased to 68.6% and 82.4% comparing with expected numbers during the last 20 years.

Mass rectal cancer screening in the general population followed by routine endoscopy for high-risk patients could decrease both rectal cancer incidence and mortality rates.