KRAS mutational status affects oxaliplatin-based chemotherapy independently from basal mRNA ERCC-1 expression in metastatic colorectal cancer patients

Background: In this study, we evaluated the possibility that KRAS mutational status might be predictive of oxaliplatin (OXA) efficacy. We also explored the role of excision repair cross complementing group-1 (ERCC-1). Methods: Ninety anti-epidermal growth factor receptor-naive advanced colorectal cancer patients were retrospectively analysed. In all patients KRAS mutational status was assessed. In 60 patients mRNA ERCC-1 expression was also investigated. Response rate (RR) and progression-free survival (PFS) after FOLFOX-6 +/- bevacizumab were evaluated according to KRAS status and mRNA ERCC-1 expression. Results: Among 90 patients 47% wild-type (wt) and 53% mutated (mt) KRAS tumours were found. Response rate was 26% in the wt KRAS group, whereas it was 56% in the mt KRAS group; the difference is statistically significant in the total sample (P = 0.008) and when only patients receiving FOLFOX-6 +/- bevacizumab as first-line are considered (P = 0.01). Progression-free survival was longer in mt than in wt KRAS patients over all patients (10 vs 8 months, respectively, P = 0.001) and in those treated as first-line (10 vs 8 months, respectively, P = 0.0069). Mt KRAS patients experienced a longer survival (24 vs 18 months; P = 0.01). ERCC-1 mRNA expression was not found to correlate with FOLFOX activity in our analysis. Conclusion: Our results suggest that activating mutation of KRAS oncogene may predict response to OXA. Basal expression of ERCC-1 mRNA does not explain the high efficacy of FOLFOX-6 in mt KRAS patients.