Purpose: We studied the efficacy of cetuximab therapy in patients with metastatic colorectal cancer (mCRC) previously treated with an oral inhibitor of the tyrosine kinase domain of the epidermal growth factor receptor.
Patients and methods: We reviewed the posttrial records of 73 patients with mCRC who participated in 1 of 3 clinical trials that examined a combination of gefitinib or erlotinib with standard cytotoxic chemotherapy. Medical and pharmacy records were used to identify patients who were subsequently treated with cetuximab-based therapy. Computed tomography scans during cetuximab-based therapy were reviewed, and the clinical activity of cetuximab was assessed by response rate using Response Evaluation Criteria in Solid Tumors and progression-free survival.
Results: Twenty-four patients with mCRC previously treated with gefitinib or erlotinib and combination cytotoxic chemotherapy who subsequently received cetuximab-based therapy were identified. While receiving cetuximab-based therapy, no patient experienced a partial or complete response; however, 3 patients (16% of patients with available scans for formal measurements) had a minor response, defined as a 15%-29.9% decrease in the sum of longest dimensions of target lesions, and 72% had stable disease. The progression-free survival was 5.1 months for all patients and 6 months for patients who had documented progression of disease while previously receiving gefitinib- or erlotinib-based therapy.
Conclusion: Cetuximab appears to have clinical benefit in patients with mCRC previously treated with a chemotherapy regimen that included an oral tyrosine kinase inhibitor of epidermal growth factor receptor. Whether these results apply to other cancer types is unknown but worthy of further study.