ISOlation Procedure vs. conventional procedure during Distal Pancreatectomy (ISOP-DP trial): study protocol for a randomized controlled trial

Background: Radical antegrade modular pancreatosplenectomy (RAMPS) is an isolation procedure in pancreatosplenectomy for pancreatic body/tail cancer. Connective tissues around the bifurcation of the celiac axis are dissected, followed by median-to-left retroperitoneal dissection. This procedure has the potential to isolate blood and lymphatic flow to the area of the pancreatic body/tail and the spleen to be excised. This is achieved by division of the inflow artery, transection of the pancreas, and then division of the outflow vein in the early phases of surgery. In cases of pancreatic ductal adenocarcinoma (PDAC), the procedure has been shown to decrease intraoperative blood loss and increase R0 resection rate by complete clearance of the lymph nodes. This trial investigates whether the isolation procedure can prolong the survival of patients with pancreatic ductal adenocarcinoma who undergo distal pancreatosplenectomy (DPS) compared with those that undergo the conventional approach. Methods/design: Patients with PDAC scheduled to undergo DPS are randomized before surgery to undergo either a conventional procedure (arm A) or to undergo the isolation procedure (arm B). In arm A, the pancreatic body, tail, and spleen are mobilized, followed by removal of the regional lymph nodes. The splenic vein is transected at the end of the procedure. The timing of division of the splenic artery (SA) is not restricted. In arm B, regional lymph nodes are dissected, then we transect the root of the SA, the pancreas, then the splenic vein. At the end of the procedure, the pancreatic body/tail and spleen are mobilized and removed. In total, 100 patients from multiple Japanese high-volume centers will be randomized. The primary endpoint is 2-year recurrence-free survival by intention-to-treat analysis. Secondary endpoints include intraoperative blood loss, R0 resection rate, and overall survival. Discussion: If this trial shows that the isolation procedures can improve survival with a similar R0 rate and with a similar number of lymph node dissections to the conventional procedure, the isolation procedure is expected to become a standard procedure during DPS for PDAC. Conversely, if there were no significant differences in endpoints between the groups, it would demonstrate justification of either procedure from surgical and oncological points of view. Trial registration: UMIN Clinical Trials Registry UMIN000041381. Registered on 10 August 2020. ClinicalTrials.gov NCT04600063. Registered on 22 October 2020.