Abstract
The role of Kirsten rat sarcoma viral oncogene homolog (KRAS) and neuroblastoma RAS viral oncogene homolog (NRAS) mutations as negative predictors for anti-epidermal growth factor receptor (EGFR) therapies in metastatic colorectal cancer (CRC) has been firmly established. However, whether the RAS mutation status plays a role as a biomarker for anti-vascular endothelial growth factor (VEGF) treatment remains controversial. Data from 93 CRC patients who received first-line cytotoxic chemotherapy with fluoropyrimidines and oxaliplatin, with or without bevacizumab, were analyzed. We investigated the association between the RAS mutation status and clinical outcomes in terms of response rate, progression-free survival (PFS) and overall survival (OS). Mutations in RAS genes were observed in 47 (52.6%) patients (45 KRAS and 2 NRAS mutations). Patients with tumours harbouring RAS mutations were less suitable for primary tumour resection, were more likely to develop lung metastases, and received bevacizumab treatment for a shorter time period compared with those with wild-type tumours. The response rate to chemotherapy did not differ according to the RAS mutation status, and there were no significant differences in PFS [RAS mutation: 12 months, 95% confidence interval (CI): 8.7-15.2 vs. RAS wild-type: 12 months, 95% CI: 9.67-14.32; P=0.857] or OS (RAS mutation: 20 months, 95% CI: 14.3-25.6 vs. RAS wild-type: 24 months, 95% CI: 18.7-29.2; P=0.631). Patients with RAS mutation vs. those with RAS wild-type exhibited a favourable trend in PFS when treated with bevacizumab (13 months, 95% CI: 6.5-19.4 vs. 10 months, 95% CI: 4.2-15.7, respectively; P=0.07) and OS (27 months, 95% CI: 18.5-35.4 vs. 15 months, 95% CI: 12.4-17.5, respectively; P=0.22). In conclusion, RAS mutations are not a prognostic marker for PFS and OS in CRC patients receiving fluoropyrimidine-oxaliplatine treatment, with or without bevacizumab. RAS mutations are not predictive of the lack of efficacy of bevacizumab, and these patients appear to benefit from anti-angiogenic treatment.