Can the Sum of Adenoma Diameters (Adenoma Bulk) on Index Examination Predict Risk of Metachronous Advanced Neoplasia?

BACKGROUND: Recent data suggest that adenoma size and number are more important predictors of metachronous colorectal neoplasia than advanced histology. Furthermore, there is poor reproducibility in diagnosing advanced histology; high-grade dysplasia and villous histology. Therefore we developed a new metric, adenoma bulk, the sum of diameters of all baseline adenomas, regardless of advanced features. GOAL: Compare the predictive value for metachronous advanced neoplasia of adenoma bulk to conventional paradigm. STUDY: Data were collected prospectively in a multicenter adenoma-chemoprevention trial (2004 to 2013). For the conventional paradigm, high-risk baseline findings were defined as ≥3 adenomas, large adenomas (≥1 cm) or adenomas with villous components or high-grade dysplasia. Adenoma bulk was examined across quartiles and as a continuous variable. Predictive characteristics (sensitivities, specificities, c-statistics) for metachronous advanced neoplasia using conventional criteria and adenoma bulk were calculated. receiver operator characteristic curves were computed using logistic regression. RESULTS: In total, 1948 adults had index and follow-up colonoscopies (mean follow-up, 45.2 mo). Those with an adenoma bulk ≥10 mm (4th quartile) had a higher metachronous advanced neoplasia risk (14.4% vs. 6.9-8.2% in lower 3 quartiles; P=0.0002). The c-statistics and sensitivities (specificity fixed at 0.73) for the adenoma bulk and conventional models were 0.587 and 0.563 (P=0.17) and 0.396 and 0.390, respectively. CONCLUSIONS: Categorizing sporadic adenoma patients as high versus low risk for metachronous advanced neoplasia by adenoma bulk of

Ornithine decarboxylase polymorphism modification of response to aspirin treatment for colorectal adenoma prevention.

BACKGROUND: Previous research suggests that the G315A single-nucleotide polymorphism in the ornithine decarboxylase (ODC) gene may be a genetic marker for risk of colorectal neoplasia and may also modify the association of aspirin use with risk. METHODS: We tested these hypotheses among participants in the Aspirin/Folate Polyp Prevention Study who were randomly assigned to placebo or to aspirin treatment (81 or 325 mg daily) and followed for 3 years for the occurrence of new adenomas. Genomic DNA from 973 subjects was analyzed for ODC genotype. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated to test the association between ODC genotype and adenoma occurrence and interactions with aspirin treatment. All statistical tests were two-sided. RESULTS: Of the 973 subjects, 54% were homozygous wild-type (GG), 7% were homozygous variant (AA), and 39% were heterozygous individuals; the allele frequencies varied statistically significantly by race and ethnicity. Among these subjects, the absolute risk of any adenoma was 45% and the risk of an advanced lesion was 10%. Overall, no association was found between ODC genotype and the occurrence of new adenomas, but genotype did modify the effect of aspirin on adenoma risk. Although aspirin treatment had no protective effect among subjects with a GG genotype, among subjects with at least one A allele, it was associated with statistically significant reduced risks of any adenoma (RR = 0.77, 95% CI = 0.63 to 0.95; P = .02, P(interaction) = .04) and of advanced lesions (RR = 0.51, 95% CI = 0.29 to 0.90; P = .02, P(interaction) = .02). Among subjects with at least one A allele, 40.8% who took aspirin versus 52.9% who took placebo developed adenomas; 7.1% versus 14.0% developed advanced lesions. CONCLUSION: ODC genotype may modify the response to aspirin treatment for colorectal adenoma prevention.

K-ras mutations in incident sporadic colorectal adenomas.

BACKGROUND: Although K-ras is the most frequently mutated protooncogene in colorectal carcinoma, the specific role and timing of K-ras mutations in colorectal carcinogenesis remains controversial. In the current study, the authors investigated associations with K-ras mutation in incident sporadic colorectal adenomas that occurred during a chemoprevention trial of calcium supplementation. METHODS: K-ras genotyping was performed on 303 colorectal adenomas that were removed from 207 participants during the follow-up phase of the Calcium Polyp Prevention Study. Mutations in codons 12 or 13 of K-ras were detected by denaturing high-performance liquid chromatography and were confirmed by direct sequencing. RESULTS: The adenomas analyzed had a mean estimated size of 0.5 cm, and 3.0% were identified with mutations (95% confidence interval [95% CI], 1.3-4.4%). These mutations were more common in larger adenomas (risk ratio [RR], 12.7 for tumors that measured > 0.5 cm vs. < or = 0.5 cm; 95% CI, 2.7-59.7), in adenomas with more advanced histology (RR, 20.6 for tubulovillous/villous vs. tubular; 95% CI, 4.4-96.0), and in adenomas that were located in the rectum compared with the colon (RR, 8.4; 95% CI, 2.3-30.5). CONCLUSIONS: Compared with previous studies, the current analysis was novel, because it focused on incident adenomas that were diagnosed within a few years of a previous "clean" colonoscopy. The results provided evidence for a very low rate of K-ras mutation among these small, early adenomas and strong support for a role of K-ras mutations in adenoma progression.