Concomitant RAS and BRAF V600E Mutations in Unresectable Metastatic CRC: A Case of Long-term Survival.

Detection of rat sarcoma virus (RAS) and B rapidly accelerated fibrosarcoma (BRAF) mutations is critical for selecting an appropriate treatment for metastatic colorectal cancer (mCRC). Although RAS and BRAF V600E mutations are traditionally mutually exclusive, they occasionally co-occur. The concurrent occurrence of RAS and BRAF V600E mutations is rare, with an incidence of < 0.001-0.05% in CRC. Treatment outcomes for cases involving concurrent occurrence of these mutations remain unclear, with reported cases exhibiting a poor prognosis of approximately 1 year. Moreover, reports on the long-term survival of patients with unresectable mCRC with concurrent mutations are lacking. The present study reports a rare case of long-term survival of over 39 months in a patient with mCRC harboring both RAS and BRAF V600E mutations, where chemotherapy alone was effective without surgical resection of the primary or metastatic lesions.