Adjuvant FOLFOX +/- cetuximab in full RAS and BRAF wildtype stage III colon cancer patients.

Background: RAS mutations have been shown to confer resistance to anti- epidermal growth factor receptor (EGFR) treatment. We analysed the results of the PETACC8 trial (cetuximab + FOLFOX vs FOLFOX) in full RAS and BRAF wildtype (WT) patients (pts) with resected stage III colon cancer. Patients and methods: Exons 2, 3 and 4 of KRAS and NRAS, and BRAF exons 11 and 15, were sequenced using the Ampliseq colon-lung cancer panel version 2, in PETACC8 trial pts who consented to translational research. The impact of cetuximab on time to recurrence (TTR), disease-free survival (DFS) and overall survival (OS) was investigated in pts with tumours harbouring RAS and BRAF WT, and RAS mutations. The prognostic value of each individual mutation was also tested. Results: Among the 2559 pts analysed, 745 pts (29%) were known to have KRAS exon 2 mutations and 163 pts (6.4%) the BRAF V600E mutation. Of the remaining 1651 pts, 1054 were assessed by NGS, showing that a further 227 pts (21%) had KRAS exon 2, 3, 4 or NRAS exon 2, 3, 4 mutations, and that 46 pts (4.4%) had a newly diagnosed BRAF mutation. Cetuximab added to FOLFOX did not significantly improve TTR, DFS or OS in pts with RAS WT or RAS and BRAF WT tumours (HR 0.77-1.03, all P > 0.05). Cetuximab addition was not either significantly deleterious in RAS mutant pts or in pts with rare RAS or BRAF mutations. In the overall trial population, NRAS and KRAS codon 61 mutations were the only rare mutations with the same pejorative prognostic value as KRAS exon 2 or BRAF V600E mutations. Conclusion: Though not significant, the clinically relevant 0.76 adjusted HR observed for DFS in favour of adding cetuximab to FOLFOX, in full RAS and BRAF WT stage III colon cancer pts, may justify a new randomized controlled trial testing EGFR inhibitors in this setting. Clinical trial number: This is an ancillary study of the PETACC8 trial: EUDRACT 2005-003463-23.

Prognostic value of KRAS mutations in stage III colon cancer: post hoc analysis of the PETACC8 phase III trial dataset.

BACKGROUND: The prognostic value of KRAS mutations in colon adenocarcinoma is controversial. We examined this question as an ancillary study of the PETACC8 phase III trial. PATIENTS AND METHODS: We analyzed the prognostic impact of KRAS exon 2 mutations in stage III colon cancer patients (n = 1657) receiving adjuvant FOLFOX ± cetuximab therapy included in the PETACC8 trial. Patients with BRAF-mutated cancers were excluded and, as no difference was found for time to recurrence (TTR) and disease-free survival (DFS) between treatment arms, both were pooled for analysis. Associations with TTR and DFS were analyzed using a Cox proportional hazards model. RESULTS: KRAS mutations were found in 638 of 1657 tumors and linked to shorter TTR (P < 0.001). However, when specific mutations were compared with wild-type, codon 12 mutations [hazard ratio (HR) 1.67, 95% confidence interval (CI) 1.35-2.04; P < 0.001] but not codon 13 (HR 1.23, 95% CI 0.85-1.79; P = 0.26) were significantly associated with shorter TTR, independently of other covariates. The interaction test showed that, regarding tumor location (distal versus proximal), KRAS genotype affects differently on recurrence (P = 0.02) and DFS (P = 0.042). Subgroup analysis showed that KRAS only affected TTR and DFS in distal tumors (n = 1043; 692 wild type; 351 mutated), with an increased risk of relapse (HR 1.96, 95% CI 1.51-2.56; P < 0.0001) for KRAS codon 12 mutations and a borderline significance for codon 13 mutations (HR 1.59, 95% CI 1.00-2.56; P = 0.051). CONCLUSION: KRAS exon 2 mutations are independent predictors of shorter TTR in patients with resected stage III distal colon cancers receiving adjuvant therapy. Future clinical trials in the adjuvant setting should consider both the tumor location and KRAS mutations as important stratification factors. CLINICAL TRIAL NUMBER: This is an ancillary study of the PETACC8 trial: EUDRACT 2005-003463-23.