A 46-year old man presented with lower right quadrant abdominal pain caused by abdominal trauma. Abscess drainage was performed after the diagnosis of retroperitoneal abscess in the ileocecal portion of the colon. Type 2 advanced cancer was found in the cecum and ascending colon. Surgery was performed after improvement of inflammation. Considering the difficulty of curative resection for retroperitoneal invasion, we first performed ileo-transverse colon anastomosis. After surgery, the patient received FOLFOX with panitumumab(Pmab)as neoadjuvant chemotherapy. After 6 courses of this regimen, contrast enhanced computed tomography revealed shrinkage of the tumor. We performed a second surgery but the tumor was unresectable because of retroperitoneal invasion. After 47 courses of chemotherapy(5-FU plus LV with Pmab), the tumor was stable and we observed no distant metastasis. A third surgery was performed, and we were able to perform ileocecal resection including the retroperitoneum. The pathological diagnosis was pT4b(SI), pN1, ly2, V2, pPM0, pDM0, R0, pStage III a. On histological examination, the efficacy of chemotherapy was evaluated as Grade 1a. The patient received adjuvant chemotherapy with capecitabine and remains healthy without any evidence of recurrence more than 10 months after surgery.