ascorbic-acid and Adenomatous-Polyps

Chemoprevention can be defined as an attempt at cancer control in which the occurrence of the disease is prevented by the administration of one (or more) chemical compounds. Main problems in chemoprevention studies are the choice of a suitable drug, the choice of an appropriate intermediate or definitive end point, and the definition of the population which should be investigated. Main classes of chemopreventive agents include vitamins, non-steroid antinflammatory drugs, minerals such as calcium or selenium, and other antioxidants such as N-acetylcysteine. Chemoprevention is particularly appealing in colorectal cancer, either because these lesions develop through a multistep process, or owing to the concept of "field carcinogenesis'. Between 1985 and 1990 we carried out a controlled study in which antioxidant vitamins or lactulose were used in an attempt to prevent the recurrence of colorectal polyps after their endoscopic removal. Among the 209 patients who could be evaluated, polyps recurred in 5.7% of the individuals who were given vitamins (A, C and E), 14.7% of patients given lactulose and 35.9% of untreated controls (chi 2 = 17.1, P < 0.001). The study suggested that either antioxidant vitamins or lactulose could be effective in reducing the recurrence rate of adenomatous polyps. In a subsequent on-going study, lower doses of the same vitamins were tested versus N-acetylcysteine (600 mg/day) or no treatment. Preliminary results showed a 40% reduction of the recurrence of polyps (versus controls) in individuals given N-acetylcysteine, while the effect of lower doses of vitamins was less appreciable. Definitive results of the study should be available by the end of 1998.

Topics: Acetylcysteine; Adenomatous Polyps; Ascorbic Acid; Chemoprevention; Colorectal Neoplasms; Gastrointestinal Agents; Humans; Lactulose; Neoplasm Recurrence, Local; Vitamin A; Vitamin E

People who consume a diet high in vegetables and fruits have a lower risk of cancer of the large bowel. Antioxidant vitamins, which are present in vegetables and fruits, have been associated with a diminished risk of cancers at various anatomical sites. We conducted a randomized, controlled clinical trial to test the efficacy of beta carotene and vitamins C and E in preventing colorectal adenoma, a precursor of invasive cancer.. We randomly assigned 864 patients, using a two-by-two factorial design, to four treatment groups, which received placebo; beta carotene (25 mg daily); vitamin C (1 g daily) and vitamin E (400 mg daily); or the beta carotene plus vitamins C and E. In order to identify new adenomas, we performed complete colonoscopic examinations in the patients one year and four years after they entered the study. The primary end points for analyses were new adenomas identified after the first of these two follow-up examinations.. Patients adhered well to the prescribed regimen, and 751 completed the four-year clinical trial. There was no evidence that either beta carotene or vitamins C and E reduced the incidence of adenomas; the relative risk for beta carotene was 1.01 (95 percent confidence interval, 0.85 to 1.20); for vitamins C and E, it was 1.08 (95 percent confidence interval, 0.91 to 1.29). Neither treatment appeared to be effective in any subgroup of patients or in the prevention of any subtype of polyp defined by size or location.. The lack of efficacy of these vitamins argues against the use of supplemental beta carotene and vitamins C and E to prevent colorectal cancer. Although our data do not prove definitively that these antioxidants have no anticancer effect, other dietary factors may make more important contributions to the reduction in the risk of cancer associated with a diet high in vegetables and fruits.

Topics: Adenomatous Polyps; Aged; Antioxidants; Ascorbic Acid; beta Carotene; Carotenoids; Colonic Polyps; Colorectal Neoplasms; Confidence Intervals; Female; Follow-Up Studies; Humans; Male; Middle Aged; Risk; Vitamin E; Vitamins

The C1561T variant of the glutamate carboxypeptidase II (GCPII) gene is critical for natural methylfolylpolyglutamte (methylfolate) absorption, and has been associated with perturbations in folate metabolism and disease susceptibility. However, little is known on C1561T-GCPII as a risk factor for colorectal cancer. Therefore, this study examined whether C1561T-GCPII influences folate metabolism and adenomatous polyp occurrence.. 164 controls and 38 adenomatous polyp cases were analysed to determine blood folate and plasma homocysteine (Hcy) level, dietary intake of natural methylfolate, synthetic pteroylglutamic acid (PteGlu), vitamin C and C1561T-GCPII genotype.. In controls and cases, 7.3 and 18.4 percent of subjects respectively, were found to have the CT genotype, increasing the risk for adenomatous polyp occurrence 2.86 times (95% CI:1.37-8.0, p=0.035). Total dietary folate, methylfolate and PteGlu intake and the level of erythrocyte folate and plasma Hcy did not predict the occurrence of an adenomatous polyp. However, dietary natural vitamin C intake was associated with adenomatous polyp risk within C1561T-GCPII CT genotype subjects (p=0.037).. The findings suggest that C1561T-GCPII variation may be associated with risk for adenomatous polyp, and vitamin C may modify risk by interacting with the variant gene, its expression product and/or folate substrates.

Topics: Adenomatous Polyps; Adult; Aged; Aged, 80 and over; Ascorbic Acid; Case-Control Studies; Colorectal Neoplasms; Diet; Folic Acid; Genotype; Glutamate Carboxypeptidase II; Homocysteine; Humans; Middle Aged; Polymorphism, Single Nucleotide; Pteroylpolyglutamic Acids; Risk Factors; Tetrahydrofolates; Vitamins

A subnormal status of vitamin C has been associated with an increased risk for several malignant diseases and may play a causative role in their development. The aim of the present study was to investigate whether this occurs also in neoplasms of the colon.. We have studied dietary intake and status of vitamin C in a consecutive group of patients with adenomatous colonic polyps (n = 31) and compared it with that of patients with no such history and a normal colonic mucosa, as confirmed by colonoscopy (n = 54).. Dietary intake of this vitamin, as assessed by the dietary recall method, was similar in the two groups, as were the levels of vitamin C in plasma and leukocytes. There were no significant differences in intake of dietary fiber, fat, vitamin A, or calcium between the two groups. Lack of association between vitamin C intake or status and colonic polyps persisted after adjustment for potential confounders.. We conclude that in this population, a deficient status of vitamin C is not an important factor in colonic neoplasia.

Topics: Adenomatous Polyps; Ascorbic Acid; Colonic Polyps; Diet; Female; Humans; Leukocytes; Male; Middle Aged; Nutritional Status