Concurrent RAS and RAS/BRAF V600E Variants in Colorectal Cancer: More Frequent Than Expected? A Case Report

Concurrent NRAS-BRAF variants in metastatic colorectal cancer: a Tunisian case report

Target therapy for metastatic colorectal cancer needs the determination of KRAS, NRAS, and BRAF mutation status to identify patients resistant to anti-EGFR treatment. RAS genes (KRAS/NRAS) are mutated in 40-60% of metastatic colorectal cancer and BRAF in 5-10%. The presence of a double mutation in RAS and BRAF is rare. Therefore, RAS and BRAF mutations were considered exclusive. Herein, we describe a novel concomitant NRAS/BRAF mutation identified in a series of 865 colorectal cancer patients.

KRAS, NRAS and BRAF Mutational Profile of Colorectal Cancer in a Series of Moroccan Patients

OBJECTIVES

The present study aimed to evaluate the frequencies of KRAS, NRAS, and BRAF mutations and their possible associations with clinicopathological features in 249 Moroccan patients with colorectal cancer (CRC).

METHODS

A retrospective investigation of a cohort of formalin-fixed paraffin-embedded tissues of 249 patients with CRC was screened for KRAS/NRAS/BRAF mutations using Idylla™ technology and pyrosequencing.

RESULTS

KRAS, NRAS, and BRAF mutations were revealed in 46.6% (116/249), 5.6% (14/249), and 2.4% (6/249) of patients. KRAS exon 2 mutations were identified in 87.9% of patients (102/116). KRAS G12D and G12 C were the most frequent, at 32.8% and 12.93%, respectively. Among the patients with KRAS exon 2 wild-type (wt), 27.6% (32/116) harbored additional KRAS mutations. Concurrent KRAS mutations were identified in 9.5% (11/116); including six in codon 146 (A146P/T/V), three in codon 61 (Q61H/L/R), one in codon 12 (G12 A and Q61H), and one in codon 13 (G13D and Q61 L). Among the NRAS exon 2 wt patients, 64.3% (9/14) harbored additional NRAS mutations. Concurrent NRAS mutations were identified in 28.6% (4/14) of NRAS-mutant patients. Since 3.2% wt KRAS were identified with NRAS mutations, concomitant KRAS and NRAS mutations were identified in 2.4% (6/249) of patients. KRAS mutations were higher in the >50-year-old age-group (P = .031), and the tumor location was revealed to be significantly associated with KRAS mutations (P = .028) predominantly in left colon (27.5%) and colon (42.2%) locations. NRAS mutations were most prevalent in the left colon (42.8%) and in well-differentiated tumors (64.2%).

CONCLUSION

Detection of KRAS mutations, particularly the G12 C subtype, may be significant for patients with CRC and has possible therapeutic implications. However, rare KRAS concomitant mutations in CRC patients suggest that each individual may present distinct therapeutic responses. KRAS testing alongside the identification of other affected genes in the same patient will make the treatments even more personalized by contributing more accurately to the clinical decision process. Overall, early diagnosis using novel molecular techniques may improve the management of CRC by providing the most efficient therapies for Moroccan patients.