Real-Life Distribution of KRAS and NRAS Mutations in Metastatic Colorectal Carcinoma from French Routine Genotyping.

In metastatic colorectal cancer, KRAS and NRAS genotyping is mandatory before prescription of panitumumab or cetuximab. In order to perform such molecular tests, the French National Cancer Institute has set up a nationwide network of molecular centers. We report here the percentage of these mutations according to a prospective nonselected cohort of incident metastatic colorectal carcinoma patients. A total of 6,803 patients were tested between July 1, 2013, and December 31, 2013. Overall, 49.06% of patients harbored a mutation in either KRAS or NRAS. Mutations of NRAS exons 3 and 4 were very rare. No NRAS exon 3 at c.59 or exon 4 at c.117 mutations were retrieved, and only 1 NRAS exon 4 at c.146 mutation was detected. This present cohort is likely to represent most of the incident cases of metastatic colorectal adenocarcinomas arising in France over 6 months and is to our knowledge the largest population set genotyped for these genes in this condition. This is a unique opportunity to observe the frequency of RAS mutations regardless of most inclusion bias.