K-RAS GENE MUTATION IS A USEFUL PREDICTOR OF THE SURVIVAL OF EARLY-STAGE COLORECTAL CANCERS

Mutations in the K-ras gene were found to be of predictive value in th e clinical outcome of non-small cell lung cancers, but its role in pre dicting the survival of colorectal cancer patients is still inconclusi ve. Point mutations in codon 12 or 13 of K-ras gene were analyzed in 6 4 colorectal cancer composing 4 Dukes' stage A, 34 stage B, 21 stage C and 5 stage D. DNA extracted from the paraffin-embedded tissues of th e 64 patients was amplified with the polymerase chain reaction and sub sequently analyzed by direct cycle sequencing. Thirteen of sixty-four (20%) resected colorectal cancer specimens were found to have K-ras ge ne mutation at either codon 12 or 13. Log rank tests found that K-ras gene mutation and Dukes' stage were associated with patients' survival . When stratified by Dukes' stage, the patients with mutated K-ras gen es in the stratum of stage A or B were found to have shorter survival times than those without mutated K-ras genes (P=0.003), but this was n ot the case in the stratum of stages C and D. The relative risk of mor tality in the stratum of stage A or B was 7.74 (95% confidence interva l: 1.82-34.89) by Cox regression analysis. We thereby conclude that K- ras gene mutation is a usefull predictor of the survival of early stag e colorectal cancers.