The Coexistence of RAS and BRAF Mutations in Metastatic Colorectal Cancer: A Case Report and Systematic Literature Review.

BACKGROUND AND AIMS The coexistence of RAS and BRAF mutations is extremely rare, occurring in approximately 0.05% of patients with metastatic colorectal cancer (mCRC). Starting from a case presentation, this review aims to examine the prevalence, clinical, histopathological and molecular features of tumors with concomitant mutations. METHODS Case report and systematic review. We performed a systematic literature search in PubMed and EMBASE using the following MeSH terms: "coexistence" OR "concomitant" AND "RAS" AND "BRAF" AND "colorectal cancer" from the inception of the databases onwards. RESULTS We present the case of a 53-year-old man diagnosed with metastatic rectal adenocarcinoma with both a KRAS and a BRAF mutation. The review included eleven papers reporting on a total of 30 mCRC cases with concomitant RAS and BRAF mutations. The male/female ratio was 11/5. The average age was 58.5 years. The tumor was located in nine cases on the right colon and in two cases in the left colon. 43.3% of subjects had liver metastases, and 6.6% had lung metastases. Next-generation sequencing (NGS) was used in 36.6% of cases and polymerase chain reaction (PCR) in 16.6% of cases. KRAS mutations were present in 83.3% of patients and NRAS mutations in 16.6% of patients. Survival could be assessed in 10 patients and the median was 21.1 months (about 30% lower than the survival in the general mCRC population). CONCLUSION The results of this systematic review suggest the need to design a cohort study (either prospective or retrospective) to better characterize the patients with concomitant RAS and BRAF mutations and to establish the optimal treatment for this rare situation.