ABSTRACT
BACKGROUND: The use of epidermal growth factor receptor inhibitors to treat metastatic colorectal cancer (mCRC) patients requires prior confirmation of tumour wild type (WT) RAS mutation status (exons 2/3/4 for KRAS or NRAS). This retrospective pooled analysis aims to robustly estimate RAS mutation prevalence and individual variation patterns in mCRC patients. METHOD: Individual patient data from five randomised, controlled panitumumab studies (three phase III, one phase II and one phase Ib/II) were pooled for this analysis. The phase III studies included mCRC patients independent of RAS mutation status; the phase II and Ib/II studies included mCRC patients with confirmed WT KRAS exon 2 status. Four studies conducted RAS testing using Sanger sequencing; one study used a combination of next-generation sequencing and Sanger sequencing. In order to assign overall RAS status, the mutation status of all exons 2/3/4 KRAS or NRAS was required to be known. RESULTS: Data from 3196 mCRC patients from 36 countries were included in the analysis. The overall unadjusted RAS mutation prevalence in mCRC patients was 55.9% (95% confidence interval (CI): [53.9-57.9%]), with the following distribution observed: KRAS exon 2 (prevalence 42.6% [40.7-44.5%]); KRAS exon 3 (3.8% [2.9-4.9%]); KRAS exon 4 (6.2% [5.0-7.6%]); NRAS exon 2 (2.9% [2.1-3.9%]); NRAS exon 3 (4.2% [3.2-5.4%]); NRAS exon 4 (0.3% [0.1-0.7%]). Differences in RAS mutation prevalence estimates were observed by study (p=0.001), gender (p=0.030), and by country (p=0.028). CONCLUSIONS: This analysis provides robust estimates of overall RAS mutation prevalence and individual variation patterns in mCRC patients.