Stage III & IV colon and rectal cancers share a similar genetic profile: a review of the Oregon Colorectal Cancer Registry.

BACKGROUND: Determining the molecular profile of colon and rectal cancers offers the possibility of personalized cancer treatment. The purpose of this study was to determine whether known genetic mutations associated with colorectal carcinogenesis differ between colon and rectal cancers and whether they are associated with survival.

METHODS: The Oregon Colorectal Cancer Registry is a prospectively maintained, institutional review board-approved tissue repository with associated demographic and clinical information. The registry was queried for any patient with molecular analysis paired with clinical data. Patient demographics, tumor characteristics, microsatellite instability status, and mutational analysis for p53, AKT, BRAF, KRAS, MET, NRAS, and PIK3CA were analyzed. Categorical variables were compared using chi-square tests. Continuous variables between groups were analyzed using Mann-Whitney U tests. Kaplan-Meier analysis was used for survival studies. Comparisons of survival were made using log-rank tests.

RESULTS: The registry included 370 patients: 69% with colon cancer and 31% with rectal cancer. Eighty percent of colon cancers and 68% of rectal cancers were stages III and IV. Mutational analysis found no significant differences in detected mutations between colon and rectal cancers, except that there were significantly more BRAF mutations in colon cancers compared with rectal cancers (10% vs 0%, P < .008). No differences were seen in 5-year survival rates of patients with colon versus rectal cancers when stratified by the presence of KRAS, PIK3CA, and BRAF mutations.

CONCLUSIONS: Stage III and IV colon and rectal cancers share similar molecular profiles, except that there were significantly more BRAF mutations in colon cancers compared with rectal cancers.