Biweekly cetuximab plus irinotecan as second-line chemotherapy for patients with irinotecan-refractory and KRAS wild-type metastatic colorectal cancer according to epidermal growth factor receptor expression status

Background Cetuximab plus irinotecan has been shown to be effective in metastatic colorectal cancer (mCRC) patients with wild-type (WT) KRAS and positive EGFR expressions (EGFR+). Retrospective analysis revealed that the efficacy of cetuximab was similar in mCRC patients negative (EGFR-) and positive for EGFR. However, the efficacy of cetuximab has not been assessed prospectively in EGFR- mCRC patients. Methods This was a prospective, multicenter phase II study assessed the efficacy and safety of biweekly cetuximab (500 mg/m²) and irinotecan (150–180 mg/m²) in patients with histologically proven adenocarcinoma with WT-KRAS and measurable lesion(s), either EGFR + or EGFR-, determined immunohistochemically, who failed first-line irinotecan-containing chemotherapy. The primary endpoint was response rate (RR), and the secondary endpoints included safety, progression-free survival (PFS) and overall survival (OS). Results Forty patients were enrolled; 20 EGFR + and 20 EGFR-; their baseline characteristics were balanced. The overall RR was 45% (18/40, 95% CI 29.6–60.4), 55% (11/20) in EGFR + and 35% (7/20) in EGFR- patients. Median PFS was 7.1 months (95% CI 4.8–9.4), 8.3 months in EGFR + and 4.9 months in EGFR- patients. Median OS was 18.5 months (95% CI 15.2–21.8), 17.2 months in EGFR + and 18.5 months in EGFR- patients. Grade 3 or 4 toxicities included neutropenia in 5 patients (12.5%) and febrile neutropenia/skin rash/asthenia in 2 (5%). Conclusions Biweekly cetuximab plus irinotecan as second-line treatment showed significant anti-tumor activity in patients with irinotecan-refractory mCRC and WT-KRAS regardless of EGFR expression status.