Plasma IGF-I is inversely associated with colorectal adenoma recurrence

PR-1 The IGF-I axis has been proposed to be a significant factor in the development of certain cancers, including colorectal. However, results from epidemiological studies suggest modest effects on colorectal cancer risk. Using cross-sectional and prospective study designs within the same cohort, we investigated whether plasma IGF-I, IGFBP-1, and IGFBP-3 were associated with colorectal adenoma characteristics at baseline, and whether their levels were related to odds for adenoma recurrence. Plasma levels of each marker were measured at baseline in 299 male participants in the Wheat Bran Fiber Trial who were followed for recurrence of their adenomatous lesions. In cross-sectional analyses, plasma IGF-I was significantly positively associated with the presence of adenomas with any villous features (p=0.04). In contrast, IGF-I levels were inversely associated with odds of colorectal adenoma recurrence, with ORs (95% CIs) of 0.72 (0.37-1.38) and 0.52 (0.27-1.00) for the second and third tertiles of IGF-I, respectively, as compared to the first tertile (p-trend=0.05). The inverse association was stronger for advanced adenoma recurrence (p-trend=0.04) than for non-advanced recurrence (p-trend=0.16). These results suggest that while IGF-I may have adverse effects in existing premalignant lesions of the colorectum, individuals with elevated IGF-I levels are protected from the formation of new lesions in the colorectum.