Conversion surgery for unresectable pancreatic ductal adenocarcinoma with liver metastasis at initial diagnosis: a nationwide multicenter study

Background: With recent advances in chemotherapy for unresectable pancreatic ductal adenocarcinoma (PDAC) with liver metastasis (LM), attempts have been made to resect the primary tumor in patients showing favorable responses to anti-cancer treatment (so-called “conversion surgery”; CS). This study aimed to clarify the outcomes of CS for PDAC with LM in a nationwide multicenter study. Methods: This retrospective, multicenter study was conducted as a project study of the Japan Pancreas Society and included patients with PDAC with LM at initial diagnosis, diagnosed radiologically or intraoperatively (occult LM), who underwent CS after at least 4 months of chemotherapy between 2010 and 2022. Survival outcomes and prognostic factors were analyzed. Results: 90 patients were enrolled from 31 Japanese institutions. Median duration of preoperative chemotherapy was 10.4 (range, 4.2–58.5) months, and gemcitabine plus nab-paclitaxel was the most common first-line regimen, followed by folinic acid, 5-fluorouracil, irinotecan, and oxaliplatin. Liver metastasectomy was performed in 27 patients (30%). 82 patients (91.1%) initiated adjuvant chemotherapy, and 41 (45.6%) completed it. Overall survival (OS) from initial treatment was 53.1 (95% CI 41.6–65.7) months; OS after CS was 39.7 (95% CI 24.4–55.9) months, and disease-free survival was 14.7 (95% CI 9.3–23.4) months. Preoperative normalization of carbohydrate antigen 19-9 and pathologic negative lymph node metastasis were independent prognostic factors for OS. Conclusion: CS may provide a survival benefit for highly selected patients with PDAC and LM, including those with occult lesions, who respond well to multidisciplinary treatment.