Addition of cetuximab to standard first-line chemotherapy reduces the risk for growth or further metastasis of metastatic colorectal cancer, according to results of a phase III study presented at the annual meeting of the American Society of Clinical Oncology.

“These findings suggest that we have a new option for the initial treatment of metastatic colorectal cancer,” said Eric Van Cutsem, MD, PhD, professor at University Hospital Gasthuisberg, Leuven, Belgium, and first author of the study. “Future studies will be necessary to see hw the different therapies compared with each other and to determine which treatment option is best for each patient.”

The CRYSTAL trial (Cetuximab Combined with Irinetocan in First-Line Therapy for Metastatic Colorectal Cancer) compared progression-free survival, response rate, and rate of tumor resection for 1198 patients who were randomized to FOLFIRI combination chemotherapy (5-fluorouracil, leucovorin, irinotecan) plus cetuximab or to chemotherapy alone.

Progression-free survival was significantly longer for the cetuximab group (8.9 months) than for patients who received only combination chemotherapy (8 months), a risk reduction of 15 percent. In addition, significantly more patients responded to cetuximab plus chemotherapy (46.9 percent) compared with chemotherapy alone (38.7 percent).

Overall, the number of patients undergoing complete resection was three times higher in the cetuximab group than in the chemotherapy only group. In addition, more than twice as many patients with liver metastases had their tumors completely resected in the cetuximab group (10 percent) than in the chemotherapy alone group (4.5 percent).

Side effects were generally comparable between groups, although more patients in the cetuximab group had grade 3/4 diarrhea (15.2 percent versus 10.5 percent) or grade 3 skin reactions (18.7 percent versus 0.2 percent) than patients who received only chemotherapy.