Peritoneal dissemination of ascending colon cancer demonstrating relapse-free survival for 40 months with panitumumab monotherapy: A case report

Introduction: The prognosis of metastatic colorectal cancer (mCRC) patients receiving multiple cytotoxic agents and targeted therapies (CATT) has improved, but a complete cure by CATT is still very rare. Presentation of case: We report the successful treatment of ascending colon cancer complicated by peritoneal disseminations (PDs) with panitumumab (Pmab) plus mFOLFOX6 therapy. A 67-year-old male patient was diagnosed with clinical stage IV cancer of the ascending colon with PDs, and underwent ileostomy. Eighteen courses of Pmab plus mFOLFOX6 caused remarkable tumor shrinkage and the disappearance of PDs on ECT. Laparotomy revealed tumor shrinkage and scarring at the PD sites. We performed right hemicolectomy, subtotal omentectomy, and ileostomy closure as curability B surgery. Seven months later, new PDs were detected by ECT so we resumed Pmab plus mFOLFOX6 therapy. After nine courses of treatment, the target lesion had completely disappeared. After a total of 20 courses, we changed to Pmab monotherapy as maintenance therapy because there was no recurrence. Forty months after the initiation of Pmab monotherapy, there has been no oncologic progression. Discussion: Pmab plus mFOLFOX6 treatment resulted in a complete response for PDs, which is extremely rare for CATT. Conclusion: We consider that Pmab therapy should be introduced for the treatment of mCRC complicated by PDs.