Oncological Role of Surgical Resection in Patients with Pancreatic Ductal Adenocarcinoma with Liver-Only Synchronous Metastases in a Single-Center Retrospective Study.

Background Surgical resection for liver-only synchronous metastases of pancreatic ductal adenocarcinoma remains controversial. We investigated the role of conversion surgery in patients with a favorable response to systemic chemotherapy.Methods Patients (n=49) were diagnosed liver-only synchronous metastases using staging laparoscopy or open laparotomy between 2007 and 2022. Clinical outcomes were retrospectively compared among patients who underwent conversion surgery (n=10), upfront surgery with or without short-term neoadjuvant chemotherapy (UpS/short NAC) for oligometastases and occult metastases limited to the liver (n=8), and chemotherapy only for resectable or borderline resectable disease with occult liver-only metastases (n=31). The surgical indication of conversion surgery was fixed as the ABC criteria, namely, Anatomical objective response of disappearance of liver metastases on imaging studies, Biological response of CA19-9 level decrease to <= 150 U/mL, and Conditional response of surgical fitness. In addition to the above ABC criteria, tumor disappearance at the liver was repeatedly confirmed using staging laparoscopy (laparoscopic response; L), and metabolic complete responses were confirmed using positron emission tomography-computed tomography (CT) (metabolic response; M).Results Median survival time from initial treatment was 9.9 months [95% confidence interval (CI): 8.3-10.9] in the chemotherapy group, 10.4 months (95% CI: 6.6-17.8) in the UpS/short NAC group, and 36.7 months (95% CI: 19.0-84.8) in the conversion surgery group (conversion surgery vs. UpS/short NAC, P=0.002; conversion surgery vs. chemotherapy, P<0.001; UpS/short NAC vs. chemotherapy, P=0.554). One patient in the UpS/short NAC group and three in the conversion surgery group achieved 5-year survival. Among them, two patients with initially multiple liver metastases (>= 10) in the conversion surgery group survived beyond 5 years. Only conversion surgery was a significant independent prognostic factor in a total cohort (hazard ratio; 0.173, P=0.002).Conclusions Conversion surgery, but not UpS/short NAC, may enhance survival in patients with synchronous liver metastases and favorably anatomical, biological and conditional responses to systemic chemotherapy.