Conversion surgery in patients with pancreatic cancer and peritoneal metastasis

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal malignancies globally. We have previously explored the clinical efficacy of intraperitoneal (IP) paclitaxel therapy for patients with PDAC and peritoneal metastasis, which demonstrated favourable response and disease control rates. However, the real implications of conversion surgery after IP therapy remain unclear. We conducted two multicenter clinical trials of IP therapy with paclitaxel in patients with PDAC and peritoneal metastasis. We focused on patients who underwent conversion surgery and investigated the long-term outcomes, particularly, initial recurrence patterns and long-term survival. Seventy-nine patients with PDAC and peritoneal metastasis were treated, and 33 (41.8%) patients received SP (intravenous IP paclitaxel with S-1) and 46 (58.3%) were administered GAP (intravenous gemcitabine + nab-paclitaxel combined with IP paclitaxel) combination therapy. Of the 79 patients, 16 (20.3%) underwent conversion surgery. The median time to surgery was 9.0 (range, 4.1-13.0) months after the initiation of chemotherapy. Finally, 13 (81.3%) patients underwent R0 resection. Evans grade was IIA in nine patients, IIB in four patients, III in two patients, and IV in one patient. The median overall survival time in patients who underwent conversion surgery was 32.5 (range, 13.5-66.9) months. Twelve (75.0%) patients were found to have experienced recurrence after conversion surgery. Especially, peritoneal recurrence was observed in 50% of patients as the initial recurrence pattern. The median recurrence-free survival time was 9.2 (range, 5.1-32.8) months, and three patients have survived without recurrence to date. Our IP therapy displays promising clinical efficacy with acceptable tolerability in patients with PDAC and peritoneal metastasis. Although we could observe some super-responders in the cohort, further improvements in IP therapy are warranted.