Long-term Sustained Clinical Remission of Peritoneal Metastatic Pancreatic Ductal Adenocarcinoma After Sequential Chemoradiation Therapy: A Case Report

Patients with peritoneal metastatic pancreatic ductal adenocarcinoma (pmPDAC) with high-level serum carbohydrate antigens (CAs) always suffer extremely dismal prognosis, with a median survival of several months. Herein, we reported a case of pmPDAC with high serum CAs who had long-term clinical remission with normalization of CAs after chemoradiation. In November 2019, a 64-year-old male patient was admitted to our center with a solid mass measuring 2.8×2.5×2.0cm in the body of the pancreas near the celiac trunk. Positron emission tomography-computed tomography (PET-CT) revealed an SUVmax of 4.2. The serum CA 242 level exceeded 150.0 U/ml (normal range: 0-20 U/ml), and CA 19-9 was elevated at 975.2 U/ml (normal range: 0-34 U/ml). During laparotomy, the tumor was found to encircle the celiac trunk over 180 degrees, with several small peritoneal nodules in the lesser omental cavity. Pathological examination confirmed the diagnosis of pmPDAC. Next-generation sequencing revealed RAS G12V, EGFR mutation (-), low TMB (tumor mutation burden), and MSS (microsatellite stability). The patient underwent six cycles of the AG regimen (gemcitabine plus nab-paclitaxel), resulting in significant tumor shrinkage and a sharp decline in CAs. Partial remission was achieved. However, due to intolerant neurotoxicity, the AG regimen was discontinued. Subsequently, synchronous oral fluorouracil (S1) and radiation therapy were administered. Five months after radiation treatment, all CAs normalized. Oral S1 was continued for an additional three months. Eventually, all anti-cancer drugs were stopped. Computed tomography scans indicated that the tumor still surrounded the celiac trunk and common hepatic artery. After a thorough discussion, a wait-and-see strategy was adopted. Remarkably, 32 months after stopping anti-cancer medication, the patient remains in good health, with sustained normalization of CAs. At the last follow-up, he had lived for 50 months, and the normalization of the CAs was sustained for 36 months. Although he still suffers the risk of disease progression, it is a successful case of state-of-the-art chemoradiation for a dismal pmPDAC patient.