OBJECTIVES

FOLFOX-4 and FOLFIRI are considered equivalent in terms of activity and efficacy as first-line chemotherapy in metastatic colorectal cancer (mCRC). The monoclonal antibody (mAb) cetuximab showed intrinsic activity as a single agent in mCRC and was approved in combination with CPT-11 for patients who failed previous CPT-11-based treatment. The purpose of this phase II study was to evaluate the activity and safety of FOLFOX-4 plus cetuximab in untreated mCRC patients.

METHODS

Untreated patients with measurable metastatic disease and expressing epidermal growth factor receptor (EGFR) received cetuximab at a loading dose of 400 mg/m(2), followed by weekly doses of 250 mg/m(2), in combination with the FOLFOX-4 regimen every 2 weeks for a maximum of 12 cycles, after which a maintenance program using cetuximab alone was allowed for a maximum of 6 months.

RESULTS

Eighty-two unselected patients were screened; 70 were EGFR+ and entered the trial. Of the 67 assessable patients, the objective response rate was 64.2% (95% CI: 52.5-75.5%) and the tumor growth control rate was 94% (95% CI: 88-99%). All the objective responses except 1 were confirmed. In the group of patients with initially unresectable liver disease alone, 7/33 (21%) were resected. The median time to progression (TTP) and overall survival (OS) were 10.0 and 22.0 months, respectively. The treatment was well tolerated, with no treatment-related deaths, while 24.2% of the patients were affected by cutaneous toxicity of grade >2. Mutational analysis of the KRAS and BRAF genes was retrospectively performed on 35 of the 69 patients treated with cetuximab (51%). KRAS was mutated in 13 out of the 35 cases (37%), whereas no mutations were detected in the BRAF gene. A trend toward an association between KRAS mutations and objective response to treatment (p = 0.07) was demonstrated. Analysis of survival showed that patients harboring KRAS mutations had a trend toward worst TTP (p = 0.14) confirmed by age- and sex-adjusted Cox multivariate regression (hazard ratio, HR = 0.62; 95% CI: 0.36-1.06; p = 0.08). Indeed, KRAS mutations were significantly associated with worst OS in both unadjusted analysis (p = 0.047; log rank test) and age- and sex-adjusted Cox multivariate regression (HR = 0.458; 95% CI: 0.248-0.847; p = 0.01).

CONCLUSIONS

These results suggest that the combination of FOLFOX-4 plus cetuximab is very active and obtains long TTP with an acceptable toxicity profile. Indeed, our results are in line with recent findings from phase II and phase III randomized studies providing strong evidence that the efficacy of anti-EGFR mAb is confined to patients with wild-type KRAS mCRC. Investigation of other predictive biomarkers may be useful to further define the responder population.