**3. Prevalence and clinical features of BRAF MT CRC**

BRAF mutations have been found in 7–10% of patients with metastatic CRC [7, 10]. BRAF MT CRC has been associated with a particular phenotype in multiple studies and meta-analysis and specifically pertaining to the BRAF V600E mutation. BRAF tumours are more prevalent in women and in patients >70 years of age. BRAF is not associated with age at diagnosis of less than 60 years [11]. BRAF mutation is more prevalent in proximal colon tumours and is rarely found in the left colon [7]. Histopathology also differs, with 60% of BRAF MT tumours being poorly differentiated and a higher rate of mucinous pathology [12]. There is an association with larger primary tumours. BRAF MT CRC is also associated with a high rate of peritoneal metastases and less lung and liver-limited disease [13–15]. In contrast, most non-V600 mutations were more likely to be lower grade and left-sided tumours with a greater overall survival [16, 17], except for codon 601/597 mutations which behave similarly to V600E MT CRC [18].
