Claus-Henning Köhne

BACKGROUND: We investigated the efficacy of cetuximab plus irinotecan, fluorouracil, and leucovorin (FOLFIRI) as first-line treatment for metastatic colorectal cancer and sought associations between the mutation status of the KRAS gene in tumors and clinical response to cetuximab. METHODS: We randomly assigned patients with epidermal growth factor receptor-positive colorectal cancer with unresectable metastases to receive FOLFIRI either alone or in combination with cetuximab. The primary end point was progression-free survival. RESULTS: A total of 599 patients received cetuximab plus FOLFIRI, and 599 received FOLFIRI alone. The hazard ratio for progression-free survival in the cetuximab-FOLFIRI group as compared with the FOLFIRI group was 0.85 (95% confidence interval [CI], 0.72 to 0.99; P=0.048). There was no significant difference in the overall survival between the two treatment groups (hazard ratio, 0.93; 95% CI, 0.81 to 1.07; P=0.31). There was a significant interaction between treatment group and KRAS mutation status for tumor response (P=0.03) but not for progression-free survival (P=0.07) or overall survival (P=0.44). The hazard ratio for progression-free survival among patients with wild-type-KRAS tumors was 0.68 (95% CI, 0.50 to 0.94), in favor of the cetuximab-FOLFIRI group. The following grade 3 or 4 adverse events were more frequent with cetuximab plus FOLFIRI than with FOLFIRI alone: skin reactions (which were grade 3 only) (in 19.7% vs. 0.2% of patients, P<0.001), infusion-related reactions (in 2.5% vs. 0%, P<0.001), and diarrhea (in 15.7% vs. 10.5%, P=0.008). CONCLUSIONS: First-line treatment with cetuximab plus FOLFIRI, as compared with FOLFIRI alone, reduced the risk of progression of metastatic colorectal cancer. The benefit of cetuximab was limited to patients with KRAS wild-type tumors. (ClinicalTrials.gov number, NCT00154102.)

PURPOSE: The addition of cetuximab to irinotecan, fluorouracil, and leucovorin (FOLFIRI) as first-line treatment for metastatic colorectal cancer (mCRC) was shown to reduce the risk of disease progression and increase the chance of response in patients with KRAS wild-type disease. An updated survival analysis, including additional patients analyzed for tumor mutation status, was undertaken. PATIENTS AND METHODS: Patients were randomly assigned to receive FOLFIRI with or without cetuximab. DNA was extracted from additional slide-mounted tumor samples previously used to assess epidermal growth factor receptor expression. Clinical outcome according to the tumor mutation status of KRAS and BRAF was assessed in the expanded patient series. RESULTS: The ascertainment rate of patients analyzed for tumor KRAS status was increased from 45% to 89%, with mutations detected in 37% of tumors. The addition of cetuximab to FOLFIRI in patients with KRAS wild-type disease resulted in significant improvements in overall survival (median, 23.5 v 20.0 months; hazard ratio [HR], 0.796; P = .0093), progression-free survival (median, 9.9 v 8.4 months; HR, 0.696; P = .0012), and response (rate 57.3% v 39.7%; odds ratio, 2.069; P < .001) compared with FOLFIRI alone. Significant interactions between KRAS status and treatment effect were noted for all key efficacy end points. KRAS mutation status was confirmed as a powerful predictive biomarker for the efficacy of cetuximab plus FOLFIRI. BRAF tumor mutation was a strong indicator of poor prognosis. CONCLUSION: The addition of cetuximab to FOLFIRI as first-line therapy improves survival in patients with KRAS wild-type mCRC. BRAF tumor mutation is an indicator of poor prognosis.

PURPOSE: The phase III CRYSTAL study demonstrated that addition of cetuximab to fluorouracil, leucovorin, and irinotecan (FOLFIRI) significantly improved overall survival, progression-free survival, and objective response in the first-line treatment of patients with KRAS codon 12/13 (exon 2) wild-type metastatic colorectal cancer (mCRC). Outcome was reassessed in subgroups defined by extended RAS mutation testing. PATIENTS AND METHODS: Existing DNA samples from KRAS exon 2 wild-type tumors from CRYSTAL study patients were reanalyzed for other RAS mutations in four additional KRAS codons (exons 3 and 4) and six NRAS codons (exons 2, 3, and 4) using beads, emulsion, amplification, and magnetics technology. No tissue microdissection was performed. A ≥ 5% mutant allele cutoff was used to call mutations. RESULTS: Mutation status was evaluable in 430 (64.6%) of 666 patients with KRAS exon 2 wild-type tumors. Other RAS mutations were detected in 63 (14.7%) of 430 patients. In those with RAS wild-type tumors, a significant benefit across all efficacy end points was associated with the addition of cetuximab to FOLFIRI. In patients with other RAS tumor mutations, no difference in efficacy outcomes between treatment groups was seen. The safety profile in RAS subgroups was similar and in line with expectations. CONCLUSION: In the first-line treatment of mCRC, patients with RAS wild-type tumors derived a significant benefit from the addition of cetuximab to FOLFIRI; patients with RAS tumor mutations did not. Molecular testing of tumors for all activating RAS mutations is essential before considering anti-epidermal growth factor receptor therapy, thereby allowing the further tailoring of cetuximab administration to maximize patient benefit.