Low-dose aspirin has a moderate chemopreventive effect on adenomas in the large bowel.

OLIC ACID AND ITS DERIVATIVES (folate) are essential nutrients in humans and play an important role in nucleotide synthesis and methylation reactions. 1 Folate deficiency leads to macrocytic anemia, and abundant evidence indicates that even in well-nourished western populations, folate supplementation reduces the risk of neural tube defects. 2 Considerable epidemiological evidence suggests that a low-folate diet is associated with an increased risk of colorectal neoplasia, 3-5 particularly in concert with alcohol, which can antagonize the metabolism of folate. 6,7 Much animal data support an antineoplastic effect of folate. However, in some animal studies, folate deficiency protects against, and supplementation increases, experimental carcinogenesis. 3 For editorial comment see p 2408.

Background & Aims Limited data exist regarding the actual risk of developing advanced adenomas and cancer following polypectomy or the factors that determine risk. Methods We pooled individual data from 8 prospective studies comprising 9167 men and women aged 22 to 80 with previously-resected colorectal adenomas to quantify their risk of developing subsequent advanced adenoma or cancer as well as identify factors associated with development of advanced colorectal neoplasms during surveillance. Results During a median follow-up of 47.2 months, advanced colorectal neoplasia was diagnosed in 1082 (11.8%) of the patients, 58 of whom (0.6%) had invasive cancer. Risk of a metachronous advanced adenoma was higher among patients with 5 or more baseline adenomas (24.1%; SE=2.2) and those with an adenoma 20 mm in size or greater (19.3%; SE=1.5). Risk factor patterns were similar for advanced adenomas and invasive cancer. In multivariate analyses, older age (P <0.0001 for trend) and male sex (odds ratio [OR], 1.40; 95% confidence interval [CI] 1.19–1.65) were significantly associated with increased risk of metachronous advanced neoplasia, as were the number and size of prior adenomas (P <0.0001 for trend), the presence of villous features (OR, 1.28; 95% CI 1.07–1.52), and proximal location (OR, 1.68; 95% CI 1.43–1.98). High-grade dysplasia was not independently associated with metachronous advanced neoplasia after adjustment for other adenoma characteristics. Conclusions Occurrence of advanced colorectal neoplasia is common following polypectomy. Factors that are most strongly associated with risk of advanced neoplasia are patient age and the number and size of prior adenomas.