Validation of a genotype-based algorithm that identifies individuals with low, intermediate, and high serum CA19-9 levels in cancer-free individuals and in patients with colorectal cancer.

Background: Serum levels of Carbohydrate antigen CA19-9 are determined by the genotype of fucosyltransferases 2 and 3. To validate, possibly modify, and improve a grouping algorithm based on these genotypes. Methods: CA19-9 levels genotypes and of fucosyltransferase 2 and 3 were analyzed in cancer-free and colorectal cancer patients. Patients were assigned to groups with low (group A), intermediate (B), or high (C) CA19-9 biosynthetic activity based on a previously developed grouping algorithm based on genotype of fucosyltransferases 2 and 3. Results: Three hundred thirty-eight patients were included (n=177 cancer-free). Of cancer-free patients 7.9%, 75.7%, and 16.4% were assigned to groups A, B, and C, respectively. In colorectal cancer patients it 7.5%, 77.0%, and 15.5%, respectively. There were significant differences between median CA19-9 levels in the three groups (P<0.001) in both cohorts. The T59G single-nucleotid polymorphism in fucosyltransferase 3 had a significant influence on CA19-9 levels in cancer-free group B patients, which led to establishment of subgroups B1 and B2. However, no difference in CA19-9 levels between these subgroups was found in colorectal cancer patients. A receiver-operating characteristic showed similar areas under the curve for original group B as well as for subgroups B1 and B2. Conclusions: The grouping algorithm based on genotype of fucosyltransferases 2 and 3, which defines groups with distinct CA19-9 serum levels, was validated in cancer-free patients and in colorectal cancer patients. No clinically relevant improvement to the grouping algorithm was identified.