I. Estimate the response rate (RR) and progression-free survival (PFS) with FOLFIRI + panitumumab in patients with acquired resistance to panitumumab (or cetuximab) + irinotecan (irinotecan hydrochloride)-based therapy after a documented clinical response or prolonged PFS and following progression on a subsequent non-anti-EGFR containing regimen in extended RAS wild-type and BRAF wild-type patients.