Abstract
To elucidate the usefulness of mass screening for colorectal cancers, we analyzed 972 cases with colorectal cancer detected during a mass screening in Nagano prefecture. A total of 872, 807 mandays went into the mass screening held between 1988 and 2000. All subjects were screened by means of immunological occult blood tests in order to establish the high-risk group. If the test results for a subject were positive, we would recommend further examination, such as total colonoscopy or sigmoidoscopy plus X-ray examination of barium enema. The survival rate was analyzed through Kaplan-Meier analysis with the log-rank test. The rate of detected colorectal cancers across all groups was 0.12% (men: 0.15%; women: 0.09%), and colorectal cancers were most frequently detected in subjects in their seventies (0.23%). Early colorectal cancer (439 cases) accounted for 58.6% of all determined colorectal cancers (749 cases). Endoscopic therapy was performed in 36.4% of all determined colorectal cancer cases. Judging from the results of the analysis of tumor sizes, it has been suggested that active endoscopic therapy need not be performed in cases with protuberant lesions under 5 mml. The cause-specific 5- and 10-year survival rates were 92.6% and 88.4%, respectively. Kaplan-Meier analysis of the probability of cause-specific survival in patients with colorectal cancer according to depth of tumor infiltration showed significant differences between sm, mp, ss, and se or a (p<0.05). On the other hand, there was no significant difference between m and sm (p>0.05). Conclusion: The long-term survival rate of patients with colorectal cancer detected during mass screening was almost satisfactory. Mass screening using immunological occult blood makes it possible to detect colorectal cancer in its early stages, and may reduce mortality from colorectal cancer. Active endoscopic therapy is not recommended in cases with polypoid lesions under 5mm except special types.
