Antioxidant vitamins or lactulose for the prevention of the recurrence of colorectal adenomas

Abstract

Colonic adenomas represent the natural precursor lesions of most colorectal cancers. The treatment of choice is endoscopic polypectomy. However, after endoscopic removal, polyps recur in a large fraction of cases. Thus, we evaluated the effect of antioxidant vitamins or lactulose on the recurrence rate of adenomatous polyps. After polypectomy, 255 individuals were randomized into three groups. Group 1 was given vitamin A (30,000 IU/day), vitamin C (1 g/day), and vitamin E (70 mg/day); Group 2 was given lactulose (20 g/day); Group 3 received no treatment. Forty-six subjects had to be excluded because the histologic diagnosis was not consistent with adenoma. The remaining 209 individuals were included in the analysis according to the "intention to treat" criterion, though 34 did not adhere to the scheduled treatment or were lost during the follow-up. Subjects were followed at regular intervals for an average of 18 months. Polyps recurring before one year from index colonoscopy were considered missed by the endoscopist. In the 209 evaluable subjects, the percentages of recurrence of adenomas were 5.7 percent, 14.7 percent, and 35.9 percent in the vitamins, lactulose, and untreated groups, respectively. The fraction of subjects remaining free of adenomas, estimated by Kaplan-Meier survival curves, was significantly different among the three groups (log-rank chi-squared = 17.138; P < 0.001). Using Cox's regression analysis, treatment was the only variable that significantly contributed to the model (regression coefficient = 0.905; P < 0.001). In conclusion, either antioxidant vitamins or, to a lesser extent, lactulose lower the recurrence rate of adenomas of the large bowel and can be proposed as chemopreventive agents, at least in high-risk individuals.

Growth and Recurrence of Colorectal Polyps: A Double-Blind 3-Year Intervention with Calcium and Antioxidants

“…Some studies have been performed in patients with colorectal adenomas, an intermediary end point, examining the recurrence rate after polypectomy [37][38][39][40][41]. However, as malignant potential increases proportionately with polyp size [42,43], growth rate may be of greater importance.…”

Randomized double-blind trial of beta-carotene and vitamin C in women with minor cervical abnormalities

“…In trials of people with a history of asbestos exposure, a combined dose of beta-carotene and retinol led to a slightly elevated incidence of lung cancer (Omenn et al, 1996) whereas another study found no differences in sputum atypia over a shorter period (McLarty et al, 1995). There does not seem to be another trial that has used beta-carotene combined with vitamin C. Trials using adenomatous colonic polyps as the outcome have tested various other combinations of beta-carotene, vitamin C, vitamin E and retinol (McKeown-Eyssen et al, 1988;DeCosse et al, 1989;Roncucci et al, 1993;Greenberg et al, 1994;MacLennan et al, 1995). Only Roncucci et al (1993), who used 1000 mg vitamin C plus 70 mg alphatocopherol plus 9 mg retinol (not beta-carotene), have found a favourable effect on the recurrence rate of adenomatous polyp.…”

“…There does not seem to be another trial that has used beta-carotene combined with vitamin C. Trials using adenomatous colonic polyps as the outcome have tested various other combinations of beta-carotene, vitamin C, vitamin E and retinol (McKeown-Eyssen et al, 1988;DeCosse et al, 1989;Roncucci et al, 1993;Greenberg et al, 1994;MacLennan et al, 1995). Only Roncucci et al (1993), who used 1000 mg vitamin C plus 70 mg alphatocopherol plus 9 mg retinol (not beta-carotene), have found a favourable effect on the recurrence rate of adenomatous polyp.…”

Evidence in Favour of Lifestyle Intervention for Cancer Prevention with Special Reference to Colorectal Cancer

“…A Canadian study of patients with sporadic adenomas found no effect of supplemental vitamin C and E on the rate of recurrence of adenomas over a two-year period among 143 patients randomly assigned to vitamins or placebo (19). However, an Italian trial revealed a statistically significant reduction in the incidence of adenomas after supplementation with vitamins A, C and E (20). In the Polyp Prevention Study involving six clinical centers in the US, treatment for four years with either betacarotene or vitamins C and E did not affect the rate of occurrence of new adenomas in patients who had had an adenoma removed before entering the study (21).…”