Sustained Complete Remission after Radiofrequency Ablation for Liver Oligometastasis from Pancreatic Cancer despite Persistent Carbohydrate Antigen 19-9 Elevation: A Case Report.

INTRODUCTION: Persistent elevation of carbohydrate antigen 19-9 (CA19-9) during chemotherapy for pancreatic ductal adenocarcinoma (PDAC) is generally regarded as a marker of poor prognosis and systemic disease, often discouraging aggressive local treatment. However, the clinical significance of elevated CA19-9 levels in patients with oligometastatic recurrence remains controversial.

CASE PRESENTATION: A 69-year-old male underwent subtotal stomach-preserving pancreaticoduodenectomy for resectable pancreatic head cancer, followed by adjuvant S-1 chemotherapy. Thirty-one months after surgery, a solitary 17-mm liver metastasis in segment VI was detected, accompanied by elevated CA19-9 levels. Systemic chemotherapy with gemcitabine plus nab-paclitaxel was administered; however, CA19-9 levels continued to rise despite stable disease on imaging and no evidence of extrahepatic metastasis. Given the persistent CA19-9 elevation suggestive of possible systemic disease, hepatic resection was considered potentially overtreatment. Although radiofrequency ablation (RFA) carries an increased risk of liver abscess in patients with prior biliary reconstruction, it was selected as a less invasive local treatment. The procedure was completed without complications. Following RFA, CA19-9 levels rapidly normalized, and the patient has remained disease-free for more than 3 years without additional chemotherapy.

CONCLUSIONS: This case demonstrates that persistent elevation of CA19-9 levels during chemotherapy does not necessarily preclude long-term disease control through local therapy in selected patients with oligometastatic recurrent PDAC. Treatment decisions should be guided by a comprehensive assessment of tumor biology, metastatic distribution, and clinical context rather than tumor marker levels alone.