- Irinotecan will be administered on days 1 and 8 of every 21-day cycle as an intravenous infusion over 90 minutes. Cetuximab will be administered intravenously on days 1, 8 and 15 of every 21-day cycle. The first treatment of cetuximab is a larger dose. Beginning with the second treatment, the participant will receive a smaller dose of cetuximab.