Folic acid and prevention of colorectal adenomas: a combined analysis of randomized clinical trials.

Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
International Journal of Cancer (Impact Factor: 5.01). 07/2011; 129(1):192-203. DOI: 10.1002/ijc.25872
Source: PubMed

ABSTRACT Observational data suggest that lower folate status is associated with an increased risk of colorectal neoplasia, implying that folate may be useful as a chemopreventive agent. We conducted a combined analysis of three large randomized trials of folic acid supplementation for the prevention of metachronous adenomas in patients with an adenoma history. Participants included 2,632 men and women who had a history of adenomas randomized to either 0.5 or 1.0 mg/day of folic acid or placebo and who had a follow-up endoscopy 6 to 42 months after randomization [mean = 30.6 (standard deviation = 8.1) months]. We used random-effects meta-analysis to estimate risk ratios (RRs) and 95% confidence intervals (CIs). The RR comparing folic acid versus placebo was 0.98 (95% CI = 0.82-1.17) for all adenomas and 1.06 (95% CI = 0.81-1.39) for advanced lesions. Folic acid was associated with a nonsignificant decreased risk of any adenoma among subjects in the lowest quartile of baseline plasma folate (≤ 11 nmol/L) and no effect among individuals in the highest quartile (> 29 nmol/L, p for trend = 0.17). There was a nonsignificant trend of decreasing risk of any adenoma associated with folic acid supplements with increasing alcohol intake. During the early follow-up reported here, more deaths occurred in the placebo group than in the folic acid group (1.7% vs. 0.5%, p = 0.002). In conclusion, after up to 3.5 years of folic acid use, there is no clear decrease or increase in the occurrence of new adenomas in patients with a history of adenoma.

Download full-text


Available from: Jane C Figueiredo, Sep 26, 2014
  • Source
    • "This is thought to occur in folate replete populations when an unnaturally high folate status accelerates cell proliferation in early cancers. However, supplementation with folic acid and other B vitamins in folate deficient populations and populations where there is a high incidence of the gene for slow folate metabolism (MTHFR C677T) may decrease the risk of these cancers (Le Marchand et al., 2002; Figueiredo et al., 2011). "
    Neural Tube Defects - Role of Folate, Prevention Strategies and Genetics, 03/2012; , ISBN: 978-953-51-0317-2
  • Source
    Gastroenterology 05/2011; 141(1):16-20. DOI:10.1053/j.gastro.2011.05.020 · 13.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The risk of developing colorectal cancer is increased in patients with inflammatory bowel disease (IBD). Surveillance colonoscopy has not been shown to prolong survival and rates of interval cancer are reported to be high. Various chemopreventive agents have been clearly shown to reduce the risk of colorectal adenoma and cancer in the general population and the problems associated with colonoscopic surveillance have led to increasing interest in utilising chemopreventive strategies to reduce the risk of colorectal cancer in patients with inflammatory bowel disease as well. Continuing colonic inflammation has been shown to be important in the development of colorectal cancer and therefore anti-inflammatory agents have been considered potential chemopreventive agents. As present no agents have been shown to have indisputable chemopreventive activity in IBD but 5-ASAs and thiopurine analogues by reducing inflammation are likely to have some chemopreventive activity and will often be indicated for disease control. More studies are needed using agents such as aspirin and calcium which have been shown to be chemopreventive in sporadic colorectal neoplasia.
    Best practice & research. Clinical gastroenterology 08/2011; 25(4-5):593-606. DOI:10.1016/j.bpg.2011.09.003 · 3.28 Impact Factor
Show more