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Background: The nutrient folate is essential for nucleotide synthesis and methylation reactions. Its role in nucleotide synthesis implies that it is needed for growing tissues, including pre-neoplastic lesions and tumors. Preliminary evidence suggests that providing folate late in the course of colon carcinogenesis may accelerate progression. Vitamin supplement use among cancer patients is generally estimated as high. This use is of concern, because folic acid, the synthetic form of folate, has much greater bioavailability and is the form present in both multivitamins and single supplements.

Objective and Methods: Within a population-based population of 758 patients with colorectal cancer (stages I-IV, ages 20-74), recruited between 1998 and 2002 through the Seattle Colorectal Cancer Family Registry (CCFR), we evaluated supplement use prior to and post diagnosis. Eligible patients had completed both baseline and 4-y follow-up questions on use of multivitamins and folic-acid supplements (combined in this analysis as folic-acid containing supplements, FAS). Use was defined as “at least 2/week for >1 month”.

Results: Use of FAS increased from 46.0% prior to diagnosis to 65.3% post-diagnosis. Among “never users” prior to diagnosis, 36.8% reported using FAS post-diagnosis. Similarly, 60.9% of “former users” and 85.1% of “current users” prior to diagnosis used FAS post-diagnosis. The increase in FAS use was comparable among colorectal cancer patients <60 yrs (42.1% to 65.4%) versus >60 years (48.8% to 65.3%). Women were somewhat more likely to initiate FAS use post diagnosis (men 46.7% to 61.9%; women 45.4% to 68.9%). There were no substantial differences by first-degree family history (FH) of colorectal cancer, although supplement use was higher among those with a FH (no FH 45.7% to 64.2%; FH+ 47.7% vs 70.5%).

Discussion: These descriptive analyses suggest that use of folic-acid containing supplements in the population is high and increases substantially after a diagnosis with colorectal cancer. The use of FAS by two thirds of colorectal cancer patients is concerning, because of folate’s potential role in fostering the growth of disseminated colonic lesions or metastases. FAS may also interact with 5-fluorouracil, which targets folate metabolism and is the main chemotherapeutic agent used in the adjuvant therapy of colon cancer.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA