Is active exercise effective in preventing metachronous advanced colorectal neoplasm after polypectomy?

Abstract

Recently, Chang et al. reported that an active exercise habit after polypectomy, a surrogate for a more active lifestyle, is associated with a lower risk for developing metachronous advanced colorectal neoplasm.1 In their study, a total of 1820 subjects comprised the study cohort and 86 (4.73%) of them developed metachronous advanced colorectal neoplasm. They showed that an active exercise habit after polypectomy was associated with a lower risk of metachronous advanced colorectal neoplasm (adjusted hazard ratio [aHR] 0.57, 95% confidence interval [CI] 0.35–0.91) and that such protective effect from exercise was specific for subjects having advanced neoplasm at screening colonoscopy (aHR 0.32, 95% CI 0.11–0.94). From the results of this study, it is concluded that patients with advanced colorectal tumors, especially after polypectomy, should be advised on aggressive lifestyle changes such as active exercise habits. In addition, the results of this study show the potential to use each colonoscopy as an opportunity to educate more active exercise habits in screening colonoscopy, especially for patients with advanced colonic rectal neoplasms. The strength of their study is that they use a detailed, validated questionnaire prior to each colonoscopy and can perform a semi-quantitative analysis of the subject's physical activity level at various time points. There are several possible causes for active exercise to suppress the development of metachronous neoplasms. One might be the problem of central obesity and insulin resistance. Correlation between metabolic status and metachronous advanced colorectal neoplasms was not significant in the present study, but in subjects with baseline central obesity and elevated fasting blood glucose, metachronous colorectal neoplasms was occurring more. To pursue this metabolic relationship rigorously, changes in insulin resistance and fasting blood glucose levels should be indicated at the time of discovery of metachronous colorectal neoplasms with and without active exercise intervention. Another possibility would be changes in the gut microbiota due to exercise. Active exercise activates colonic motility and is thought to improve constipation.2 At the same time, the metabolism of gut microbiota is activated, and active exercise is thought to suppress the retention of the pathogenic bacteria such as Fusobacterium nucleatum3, 4 that has recently been implicated in colorectal cancer.5 Increased branched chain amino acids have also been reported to be associated with multiple polypoid adenomas and intramucosal neoplasms.6 On the other hand, short-chain fatty acids produced by gut bacteria may also change. In our recent study, Salmonella infection to mouse intestine was attenuated by the pre-administration of short-chain fatty acids (SCFAs),7 suggesting that SCFAs in the intestine play a role as defense against pathogenic bacterial invasion or immune activation. Barton et al.8 recently reported that athletes had relative increases in fecal metabolites such as microbial produced SCFAs (acetate, propionate and butyrate) associated with enhanced muscle turnover and overall health when compared with control groups, indicating that active exercise habit may contribute to the production of short-chain fatty acids in the intestinal tract. An important message is that at the time of endoscopic resection of advanced colorectal neoplasm, instructing the patient to adopt active exercise habits can prevent the development of metachronous colorectal neoplasm. Author declares no conflict of interest for this article. None.