Interventions

In the isolation procedure group, transection of the root of the splenic artery (SA) and the pancreatic transection are performed first, followed by division of the splenic vein (mandatory procedure). At that time, the branch from the splenic artery (dorsal pancreatic artery), the branch to the splenic vein (left gastric vein, inferior mesenteric vein), and the short gastric artery and vein are also disconnected as soon as possible (recommended procedure). An operation to lift up the pancreatic neck from the dorsal portal vein or superior mesenteric artery to expose the splenic vein (so-called tunneling) is allowed. After that, lymph node dissection, such as of hepatoduodenal mesentery (lymph node No.12) [19], and around the common hepatic artery perimeter (lymph node No.8) [19], and lymph node dissection around the SMA (lymph node No.14p) [19] are performed (recommended procedure). At the end of the resection operation, the pancreatic body/tail and the spleen are mobilized and removed (required procedure) by detachment of the retroperitoneum. Strasberg et al. described the division of the left gastric artery as an optional step that may be omitted; otherwise, this procedure is identical to the RAMPS procedure [5].

In the conventional procedure group, first, the pancreatic body and tail and spleen are mobilized by detachment of the retroperitoneum (mandatory procedure). The regional lymph nodes of the pancreatic body/tail, such as the hepatoduodenal mesentery (lymph node No. 12) [19] and the common hepatic artery perimeter (lymph node No. 8) [19], are removed (recommended procedure) and dissection of lymph nodes (lymph node No.14p) [19] around the SMA (recommended procedure). After dissection of the gastro-splenic ligament and pancreatic transection, the splenic vein is divided at the end of the resection procedure (required procedure), although pancreatotomy or division of the SA in early phases is allowed to prevent bleeding and secure a safe field of view.

In both groups, the spleen is resected with the pancreas. The direction of the detachment of the pancreatic body/tail from the retroperitoneum is recommended to proceed from the right side to the left side. Lymph node dissection shall be regional lymph node dissection (lymph node Nos. 8a, 8p, 12a, 12p, 11p, 11d, and 14p) in the Classification of Pancreatic Carcinoma of Japan Pancreas Society (Fourth English Edition) [19] (recommended procedure). As a general rule, the nerve plexus around the SMA is preserved all around (recommended procedure).

In both groups, the approach of open surgery, laparoscopic surgery, and robotic surgery is left open to the decision of the operators.

To ensure safety, conversion from laparoscopic or robotic surgery to open surgery based on the intraoperative findings such as uncontrollable bleeding or severe adhesion is acceptable. However, the conversion from open surgery to laparoscopic or robotic surgery is not specified.

For safety, with consideration of bleeding prevention, it is permissible to perform adhesion detachment around the spleen.

Hemostasis (compression, suturing, branch transection) is permissible if there is bleeding from portal veins.

The method of pancreatic transection or the method of closing the pancreatic stump is left open to the decision of the operators.

Splenic vein resection together with the pancreatic parenchyma after isolation of the parenchyma during DPS is acceptable if it can be safely performed.

Combined resection of the surrounding organs other than the spleen (stomach, large intestine, etc.) is allowable. However, if the surgical procedure is changed to portal vein resection, celiac artery resection, exploratory laparotomy, etc. during the operation, it will be considered as a deviation, and the protocol treatment will be stopped according to the criteria for discontinuing protocol treatment. Patients with protocol deviation must be followed in an intention-to-treat analysis.

If essential procedures cannot be performed in either group, it is considered to be a deviation and the protocol treatment is stopped according to the criteria for discontinuing protocol treatment. Whether or not the recommended procedure is performed is not treated as a target of deviation judgment.