Novel genetic and epigenetic alterations in ... - Ous-research.no

On the assumption that DNA repair and cell cycle genes significantly influence thedevelopment and prognosis of MSI tumors, genes falling into these categories were sortedaccording to mutation frequency, and those displaying mutations in over 15% of sampleswere included regardless of sample number. Finally, genes that are considered by Woerner etal. to be true target genes in MSI CRC were included,[14] resulting in a total of 41 genes.Statistics2 x 2 contingency tables were analyzed using Fisher’s exact test. 3 x 2 tables were analyzed bythe Pearson 2 test. Due to a low number of samples, Mann-Whitney Wilcoxon test wasperformed to evaluate the difference in total number of mutations in the right-sided andrectal tumors. An independent T-test was performed when comparing continuous normallydistributed data between two groups. Kruskal-Wallis one-way analysis of variance was usedto test the equality of mutation frequencies among the test and validation series as well as theliterature.Five year disease-free survival was analyzed using Kaplan-Meier plots, and the Breslow testwas used to compare the equality of the survival functions. Cox regression for multivariateanalyses was used to determine the parameters with the greatest impact on survival. P-valuesform the likelihood ratio test was used. Disease-free survival was defined as the time fromdiagnose to the first event of either death from disease, locally recurrent disease or distantmetastasis, while death from other reasons and death from surgery were censored. All Pvalues were derived from statistical tests using the SPSS 15.0 software (SPSS, Chicago, IL,USA), and considered statistically significant at P < 0.05.9