Phase II trial of imatinib, bevacizumab and cetuximab plus modified FOLFOX-6 in advanced untreated colorectal cancer

Abstract

e15030 Background: Imatinib inhibits PDGFR interfering with pericytes, the structural support to newly formed tumor blood vessels. It may thus synergize with bevacizumab. Microenvironment and tumor targeted agents along with chemotherapy could be a promising add-on approach. Methods: cetuximab 500 mg/m2, bevacizumab 5 mg/kg and modified FOLFOX-6 were given i.v. on day 1 and repeated every 2 weeks. Imatinib 400 mg/day per os was given continuously. Due to the cost and potential toxicity of the combination, the endpoint for this phase II study was very ambitious: at least 25% of complete response (medically or surgically achieved), lasting a minimum of 12 months in advanced untreated colorectal cancer patients with clearly unresectable disease. Results: Of 26 patients (16 with 1 site of disease), 17 completed the first 4 months of treatment according to the protocol, while 9 had to discontinue one biologic drug due to side effects (5 cetuximab, 3 imatinib and 1 bevacizumab). Grade 3–4 toxicity: diarrhea 12%, neutropenia 24%, skin rash 24%, hypersensitivity reactions 16%, asthenia 8%, neuro 8%. All patients were evaluable for response. Eleven responses ( 1 CR and 10 PR), 13 SD and 2 PD were observed, corresponding to 42% RR ( 95% CI = 23–61). The minimum follow up is 12 months; median PFS is 10 months. One patient among responders underwent radiofrequency ablation and 17 patients underwent surgery: 8 R-0, 3 R-1, 5 R-2 and one exploratory laparotomy. Major post surgical complications occurred in 5/17 patients. No evidence of macroscopic disease after the entire treatment plan was obtained in 13/26 patients: 12 surgical and 1 medical CR. Seven/13 were disease free at 6 months, but only 3 were still disease free at 12 months. ERCC1, ERCC2/XDP, GSTP1,TS,EGF, COX2, CYCLIN D, FCgR polymorphisms and K-RAS mutations were evaluated on all 26 patients, but no correlations were found with clinical outcome. Conclusions: The triple combination of biologics with modified FOLFOX-6 is feasible and tolerable as initial aggressive treatment. The primary endpoint of the study was not met . In fact the activity, 42% RR, was not outstanding and the high resectability rate, 69%, is misleading in the light of the short duration of the surgically induced CR. [Table: see text]