Spleen-Preserving Distal Pancreatectomy:
Distal pancreatectomy is defined as the removal of the pancreatic tail to the left of the superior mesenteric artery (1). There are essentially two variants: an oncological variant with complete lymphadenectomy and splenectomy, and a spleen-preserving variant first described in 1943 (1).
Reasons for preserving the spleen include the potentially negative consequences of splenectomy, such as the risk of severe infections (OPSI syndrome = overwhelming postsplenectomy infection) and generally increased postoperative morbidity (2).
Classic indications for a possible spleen-preserving distal pancreatectomy are generally masses of the pancreatic tail that are not considered primary carcinomas of the pancreas. These include findings such as benign cystic masses of the pancreatic tail with potential for malignancy, focal chronic pancreatitis related to the pancreatic tail, metastases from other malignancies (e.g., renal cell carcinoma), theoretically trauma to the pancreatic tail with duct injuries or uncontrollable bleeding, and neuroendocrine tumors according to the ENETS guidelines (3). In addition to primary pancreatic malignancies or suspicious masses, other contraindications for spleen preservation include local tumor extension, splenomegaly, or extension of inflammation to the splenic hilum (4). Generally, central vascular invasion by malignant processes, portal vein thrombosis with massive venous collaterals, acute pancreatitis, advanced liver cirrhosis, or anesthesia unfitness due to severe cardiovascular risk factors argue against surgical intervention with or without spleen preservation. Patients with an ECOG Performance Status ≥ 2 have a poorer prognosis.
Regarding the implementation of spleen preservation, a DRG statistic from 2009-2013 showed an almost 50:50 distribution between spleen-resecting and spleen-preserving procedures (5).
Centralization and Minimum Volumes in Pancreatic Surgery
In high-volume centers for pancreatic surgery, postoperative mortality can be reduced and survival increased [42, 43, 44]. Against this background, the Joint Federal Committee in Germany has decided to increase the minimum volumes for complex pancreatic procedures from the current 10 to 20 resections per year starting in 2024.
Minimally Invasive/Robot-Assisted Distal Pancreatectomy
Laparoscopic techniques and robotics in pancreatic cancer must be differentiated with regard to distal and pancreatic head resections. The proportion of minimally invasive distal pancreatectomies was still very low at about 5% in the work of Nimptsch from 2016 (5).
Currently, there are no data on the proportion of robot-assisted distal pancreatectomies with spleen preservation performed in Germany. However, robotics has increasingly established itself in pancreatic surgery in recent years. Due to the technical advantages of robotics, a significantly higher and especially increasing rate of minimally invasive distal pancreatectomies is to be expected.
While robot-assisted pancreaticoduodenectomy is considered technically highly demanding and requires a long learning curve, distal resection is technically much simpler due to the absence of any anastomoses (6).
Thus, distal pancreatectomy is suitable at pancreatic centers with laparoscopic experience during the implementation phase of a robotics program as an ideal "entry" into robotic surgery due to its characteristics. After all, an isolated resection without reconstruction is performed. Initially, procedures on benign findings that appear uncomplicated are recommended. After the first successes, the spectrum can then be expanded to malignant tumors and resections in pancreatitis. Extended distal pancreatectomies with vascular reconstructions, as well as multivisceral resections with distal pancreatectomies, are robot-assisted possible at centers with extensive robotic and pancreatic surgical experience. Of course, this always requires a preoperative risk-benefit assessment, which may also favor a primarily open approach.
For laparoscopic distal pancreatectomy, the patient-blinded randomized controlled LEOPARD study from the Netherlands showed faster functional recovery and less blood loss (7). While overall complication rates showed no significant difference, detailed analysis revealed some noteworthy specific differences, such as a relative risk for postoperative pancreatic fistula of 1.72 in the minimally invasive group (7).
In the combined analysis of the LEOPARD and LAPOPS studies, the data on the non-inferiority of the minimally invasive approach were confirmed (8).
Based on the DGAV register StuDoQ|Pancreas, a propensity score analysis was conducted, showing that the minimally invasive approach increased the rate of spleen-preserving procedures compared to the open approach, shortened hospital stay, while prolonging operation time and increasing the rate of readmissions (9).
The advantages of open surgery compared to minimally invasive distal pancreatectomy are seen in the easier management of intraoperative complications such as vascular injuries, better estimation of the extent of resection through palpation, and generally shorter procedure times (10).
When considering robot-assisted distal pancreatectomy in isolation, the data consist of monocentric and mostly retrospective studies on feasibility and perioperative outcomes. Some retrospective studies with small case numbers from recent years compare the results of robot-assisted with those of laparoscopic or open surgery in distal pancreatectomy (11, 12, 13, 14, 15, 16, 17) robotically and openly (18, 19) as well as all three approaches (20, 21, 22, 23, 24, 25, 26, 27).
Some advantages of robotics have always been demonstrated. For example, Weng et al. showed in a propensity score-matching analysis that robotics can reproduce the advantages of laparoscopic surgery (26).
Morelli et al. increased the rate of spleen-preserving operations for benign pancreatic cysts with the robot-assisted approach compared to the open approach (27).
Also, compared to laparoscopy, a conceivable advantage of robotics due to improved ergonomics and visualization through the telemanipulator would be a higher rate of spleen-preserving operations for benign masses. This result can indeed be demonstrated by individual studies (28, 29, 30).
However, the data is not clear. A prospective non-randomized monocentric study could not confirm this possible advantage (12).
A retrospective analysis of the National Cancer Database of the American College of Surgeons found that the robot-assisted approach was associated with lower 90-day mortality and fewer extended hospital stays compared to the open approach (31).
Two meta-analyses from recent years summarize the results of monocentric observational studies (32, 33).
The meta-analysis by Memeo summarizes 9 studies, four of which are comparative and contrast the laparoscopic with the robot-assisted approach. Ultimately, no difference in perioperative outcomes was found between laparoscopic and robotic distal pancreatectomy (32). However, it is assumed that differences will emerge once centers have completed their learning curves.
The meta-analysis published by Niu et al. in 2019 summarizes the results of 17 studies with 2133 patients regarding all three procedures (robot-assisted, laparoscopic, and open) (33). Ultimately, there were no significant differences between the procedures in terms of severe perioperative complications, postoperative fistula rate, and intraoperative blood loss. Compared to laparoscopy, robotics showed a longer operation time but a shorter hospital stay and a higher rate of spleen-preserving procedures. Compared to the open approach, robotics offered a shorter hospital stay and a lower overall complication rate.
Distal pancreatectomy with splenectomy for malignant masses was investigated regarding oncological outcomes by Raoof et al. in an American registry study (34). After a median follow-up of 25 months, the robotic group (n=99) showed equally good oncological outcomes as the laparoscopic comparison group (n=605) (34).
A meta-analysis by Zhao et al. compared robot-assisted pancreatic surgery with open pancreatic surgery (35).
It includes 15 studies, with no RCT included, and concludes based on the current study situation that robotic distal pancreatectomy is associated with fewer blood transfusions, fewer lymph nodes removed, fewer complications, and a shorter hospital stay compared to open surgery. There was no significant difference between the two groups in terms of spleen preservation rate, positive resection margin, pancreatic fistula incidence, and mortality. It concludes that robot-assisted surgery is a safe and feasible alternative to open pancreatic surgery in terms of perioperative outcomes, although the evidence is still quite limited due to the lack of high-quality randomized controlled trials.
Summary
The advantages and disadvantages shown in the studies can be summarized as follows:
Robotics has so far led to longer operation times and higher costs compared to laparoscopy and open surgeries. Compared to open surgeries, both robotics and laparoscopy showed less blood loss, and patients recover faster and can be discharged sooner. There are no significant differences in severe intra- and postoperative complications across the studies. Depending on the study design and endpoints, occasional differences arise, such as a higher rate of spleen preservation with robotics compared to laparoscopy in individual studies.
Furthermore, the current evidence ultimately does not allow for a conclusive assessment and clear favoring of one approach over another at this time (2022), neither in the comparison of laparoscopic vs. open nor in the comparison of robotics with the other procedures. In particular, for the robot-assisted approach, randomized controlled trials (e.g., non-inferiority studies) are still lacking.