[Locally Advanced Rectal Cancer Presenting with Perforation That Was Successfully Resected after Preoperative Chemotherapy with mFOLFOX6 plus Panitumumab].

We report a case of locally advanced rectal cancer presenting with perforation that was successfully resected after preoperative chemotherapy. A 66-year-old woman visited our emergency room complaining of lower abdominal pain. Abdominal CT showed a rectal tumor with fluid collection and free air in the pelvis. The patient was diagnosed with panperitonitis secondary to cancerous perforation and underwent sigmoid colostomy. A biopsy specimen of the rectal tumor showed well-differentiated tubular adenocarcinoma and wild-type RAS. After 8 courses of mFOLFOX6 plus panitumumab, the tumor shrank remarkably, and radical surgery(low anterior resection with D3 lymph node dissection)was performed. Microscopic examination of the resected specimen showed that almost half of the tumor cells were replaced by histiocytes and necrotic tissue. Preoperative chemotherapy with panitumumab may be an effective treatment for RAS wild-type locally advanced colon cancer, even if the primary tumor develops perforation.