IMPORTANCE Fluorouracil-based chemotherapy combined with anti-epidermal growth factor receptor/vascular endothelial growth factor therapy is the standard first-line treatment for metastatic colorectal cancer followed by low-intensity maintenance therapy to balance the clinical efficacy and adverse effects (AEs). However, there have been concerns about the AEs of capecitabine plus cetuximab as a maintenance therapy in patients with RAS wild-type metastatic colorectal cancer. OBJECTIVE To evaluate the biological activity and safety of capecitabine plus cetuximab as a novel maintenance therapy for RAS wild-type metastatic colorectal cancer. Design, Setting, and PARTICIPANTS This phase 2 prospective clinical trial was conducted from April 29, 2016, to April 29, 2019, at 5 centers in China. Patients diagnosed as having RAS wild-type metastatic colorectal cancer were recruited to receive fluorouracil-based cytotoxic agents combined with cetuximab followed by capecitabine plus cetuximab for maintenance therapy. Forty-seven patients with histologically confirmed metastatic colorectal cancer and genetic test results showing a wild-type RAS were enrolled in maintenance therapy. INTERVENTIONS Induction therapy for patients with RAS wild-type metastatic colorectal cancer was 8 to 12 cycles of fluorouracil-based chemotherapy combined with cetuximab. After stable disease status or better was achieved, reduced-dose capecitabine plus cetuximab was administered for maintenance therapy. MAIN OUTCOMES AND MEASURES The primary end point was progression-free survival during maintenance therapy. The secondary end points were total progression-free survival, overall survival, quality of life, safety, and toxic effects of treatment. RESULTS Forty-seven patients were enrolled in maintenance therapy, with a median age of 52 years (range, 25-81 years) and 32 (68%) of them being men. The median maintenance progression-free survival was 7.2 (95% CI, 5.8-8.6) months. The median progression-free survival was 12.7 (95% CI, 11.8-15.4) months. The median overall survival was 27.4 (95% CI, 21.4-35.5) months. Grade 3 to 4 AEs during induction therapy included neutropenia (4 patients [9%]), diarrhea (4 patients [9%]), nausea or vomiting (3 patients [6%]), rash acneiform (10 patients [21%]), and hand-foot syndrome (8 patients [17%]). Grade 3 to 4 AEs during maintenance therapy included diarrhea (2 patients [4%]), rash acneiform (8 patients [17%]), and hand-foot syndrome (5 patients [11%]). CONCLUSIONS AND RELEVANCE Reduced-dose capecitabine plus cetuximab after initial chemotherapy is a novel maintenance therapy for patients with RAS wild-type metastatic colorectal cancer that achieved good outcomes and tolerable nonserious AEs.