COLORECTAL-CANCER AND FOLATE STATUS - A NESTED CASE-CONTROL STUDY AMONG MALE SMOKERS

Evidence is accumulating that folate, a B vitamin found in green leafy vegetables, may affect the development of neoplasia. We examined the relationship between folate status and colorectal cancer in a case-con trol study nested within the Alpha-Tocopherol Beta-Carotene Study coho rt of male smokers 50-69 years old. Serum folate was measured in 144 i ncident cases (91 colon, 53 rectum) and 276 controls matched to cases on baseline age, clinic, and time of blood collection. Baseline dietar y folate was available from a food-use questionnaire for 386 of these men (92%). Conditional logistic regression modeling was used. No stati stically significant association was observed between serum folate and colon or rectal cancer. Although a 2-fold increase in rectal cancer r isk was suggested for men with serum folate >2.9 ng/ml and those in th e highest quartile of energy-adjusted folate intake, there was no evid ence of a monotonic dose-response, and all confidence intervals includ ed unity. For dietary folate and colon cancer, odds ratios of 0.40 [95 % confidence interval (CI), 0.16-0.96], 0.34 (95% CI, 0.13-0.88), and 0.51 (95% CI, 0.20-1.31) were obtained for the second through fourth q uartiles of energy-adjusted folate intake, respectively, compared to t he first (P for trend = 0.15). Furthermore, men with a high-alcohol, l ow-folate, low-protein diet were at higher risk for colon cancer than men who consumed a low-alcohol, high-folate, high-protein diet (OR, 4. 79; 95% CI, 1.36-16.93). This study suggests a possible association be tween low folate intake and increased risk of colon cancer (but not re ctal cancer) and highlights the need for further studies that measure dietary folate and methionine, along with biochemical measures of fola te (i.e., erythrocyte and serum), homocysteine, and vitamin B-12.