Impact of KRAS, BRAF, and PIK3CA mutations, PTEN, AREG, and EREG expression, and skin rash in metastatic colorectal cancer patients treated with cetuximab-containing salvage treatment.

Abstract

445 Background: To investigate the predictive significance of KRAS exon 2, BRAF V600E, PIK3CA exon 9 and 20 mutational status, AREG- EREG mRNA expression, PTEN protein expression and skin rash in patients with metastatic colorectal cancer (mCRC) treated with cetuximab containing salvage chemotherapy. Methods: Primary tumors from 112 mCRC patients were analyzed. The worst skin toxicity during treatment was recorded. Results: KRAS, BRAF and PIK3CA mutations were present in 37 (33%), 8 (7.2%) and 11 (9.8%) cases, respectively, PTEN was lost in 21 (19.8%) cases, AREG and EREG were overexpressed in 48 (45%) and 51 (49%) cases. In the whole study population, time to tumor progression (TTP) and overall survival (OS) was significantly lower in patients with KRAS (p=0.001 and p=0.026, respectively) or BRAF (p=0.001 and p<0.0001, respectively) mutant tumors, downregulation of AREG (p=0.018 and p=0.013, respectively) or EREG (p=0.002 and p=0.004, respectively) and in those with grade 0-1 skin rash (p<0.0001 and p<0.0001, respectively). In KRAS wt patients TTP and OS was significantly lower in patients with BRAF (p=0.0001 and p<0.0001, respectively) mutant tumors, downregulation of AREG (p=0.021 and p=0.004, respectively) or EREG (p=0.0001 and p<0.0001, respectively) and grade 0-1 skin rash (p<0.0001 and p<0.0001, respectively). TTP was significantly lower in patients with PIK3CA mutations (p=0.01) or lost PTEN (p=0.002). Multivariate analysis revealed KRAS (hazard ratio [HR] 4.3, p<0.0001), BRAF mutation (HR: 5.1, p<0.0001), EREG low mRNA expression (HR: 1.6, p=0.021) and absence of severe/moderate skin rash (HR: 4.0, p<0.0001) as independent prognostic factors for decreased TTP. Similarly, KRAS (HR 2.9, p=0.01), BRAF mutation (HR: 3.0, p=0.001), EREG low mRNA expression (HR: 1.7, p=0.021), absecence of severe/moderate skin rash (HR: 3.7, p<0.0001) and the presence of undifferantited tumours (HR: 2.2, p=0.001) were revealed as independent prognostic factors for decreased OS. Conclusions: These results underscore the potential of advanced CRCs genetic profiling in order to identify patients with different treatment response. No significant financial relationships to disclose.