Significance of fecal deoxycholic acid concentration for colorectal tumor enlargement.

Deoxycholic acid (DCA) has been shown to promote proliferation of colonic carcinoma cells in many fundamental studies. However, no large-scale prospective clinical study providing direct evidence for an association of DCA with progress of colorectal tumor development in humans has been reported to date. To address this question, we conducted a two-step epidemiological study applying enzyme-linked immunosorbent assays to measure fecal cholic acid (CA) and DCA concentrations. Firstly, we compared bile acid concentrations of fecal samples from 366 patients who had multiple colorectal tumors removed endoscopically (tumor group) with those from 24 controls without abnormality in their large intestine (control group). Secondly, the tumor group was followed-up to evaluate the association between fecal bile acid concentrations and recurrence of colorectal tumors four years later. Fecal DCA level in the tumor group were significantly higher than that in the controls, whereas there was no difference in CA levels between the two groups. In the tumor group, a subgroup with high DCA level had higher recurrence risk of large adenomas (> 3 mm) four years later than the low DCA subgroup (odds ratio:1.85, 95% confidence interval: 1.12-3.05). This trend was observed more strongly in the left side colon. In conclusion, a high fecal DCA concentration may be a promoter of colorectal tumor enlargement.