Cetuximab Maintenance Therapy in Patients with Unresectable Wild-Type RAS and BRAF Metastatic Colorectal Cancer: A Single-Institute Prospective Study

Abstract

Introduction: Cetuximab plus FOLFIRI (leucovorin, fluorouracil, and irinotecan) is the preferred first-line therapy for RAS and BRAF wild-type (RBWT) metastatic colorectal cancer (mCRC). To counter chemotherapy-induced side effects, use of maintenance therapy is suggested. Therefore, we evaluated the efficacy and safety of cetuximab maintenance therapy in patients after effective completion of first-line induction therapy.

Methods: This prospective study enrolled untreated patients with mCRC RBWT who received first-line cetuximab plus FOLFIRI therapy. Following this, patients with treatment response either entered observation (stop treatment) or maintenance treatment 1 (cetuximab plus irinotecan) groups. After 6-12 cycles of maintenance treatment 1, patients entered maintenance treatment 2 (cetuximab only). If a patient progressed on maintenance 2, cetuximab plus FOLFIRI was reintroduced. The primary end point was failure-free survival (FFS), whereas the secondary end points included disease control rate (DCR), objective remission rate (ORR), and progression-free survival (PFS). Safety events were also evaluated.

Results: Among 79 enrolled patients, 72 completed first-line treatment effectively (DCR 91.1%, ORR 63.9%) and 44 entered maintenance 1 [median PFS 1 (mPFS, maintenance 1) 6.1 months, 95% confidence interval (CI) 6.0-6.2; DCR 56.8%; ORR 22.7%]. Of them, 21 entered maintenance treatment 2 (mPFS2 8.7 months, 95% CI 3.3-14.1; DCR 28.6%; ORR 4.8%). Median FFS (mFFS) was significantly longer in the maintenance 1 group compared with the observation group [12.7 vs. 3.0 months; hazard ratio (HR) 0.202, 95% CI 0.111-0.369; P < 0.001]. Overall, mFFS was 19.0 and 9.3 months in maintenance and observation groups, respectively (HR 0.211, 95% CI 0.117-0.380; P < 0.001). Rash acneiform, mucositis, and asthenia were commonly observed adverse events during maintenance treatment.

Conclusion: Maintenance treatment with cetuximab after first-line therapy significantly improved FFS, with an acceptable safety profile in untreated patients with mCRC RBWT.

Trial registration: Retrospectively registered, 2019/10/02, Chinese Clinical Trial Registry, ChiCTR number 1900026360.

Keywords: Cetuximab; Maintenance therapy; RAS and BRAF wild-type (RBWT); Reintroduced; Unresectable metastatic colorectal cancer.