Anti-Epidermal Growth Factor Receptor Antibody Readministration in Chemorefractory Metastatic Colorectal Cancer

Background/Aim: Readministration of anti-epidermal growth factor receptor (EGFR) antibody for metastatic colorectal cancer (mCRC) after disease progression remains to be determined. Patients and Methods: Readministration of anti-EGFR antibody in mCRC patients previously refractory to anti-EGFR antibody was prospectively observed. Results: A total of thirteen patients with a median age of 60-years old and an Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1, were enrolled. The median number of previous chemotherapies was 3 (range 2-5). Prior anti-EGFR antibody in combination with cytotoxic drugs was administered in 12 patients. Anti-EGFR antibody readministration regimens were cetuximab/panitumumab plus capecitabine/S-1 (seven patients), panitumumab plus FOLFOX (three patients), cetuximab plus irinotecan (two patients), and panitumumab monotherapy (one patient). Seven patients showed stable disease following readministration and six patients showed progressive disease. The median overall survival (OS) following readministration was 228 days and the median PFS was 102 days. Patients with intervals longer than 90 days between anti-EGFR therapies exhibited more favorable survival than those with intervals shorter than 90 days. Switching of anti-EGFR antibody between treatments was observed to contribute survival. Conclusion: Anti-EGFR antibody readministration could show a modest survival benefit in mCRC patients, with the length of therapy interval and switching of antibody being important contributory factors.