What factors are associated with robotic distal pancreatectomy conversion?

We would like to comment the excellent manuscript by Müller et al. (1), titled “Conversion of robotic distal pancreatectomy: predictors and outcomes in an international multicenter study”, which was published in the prestigious Q1 journal, Annals of Surgery. This is the first major series dedicated to robotic distal pancreatectomies (RDPs) conversion. This retrospective multicenter study examined 2,452 RDPs performed at 16 international centers, of which 75 (3.1%) required conversion to open surgery. In the cases of converted RDPs, the findings revealed that operative time was longer, blood loss was greater, and patients encountered more overall complications as well as major complications. Additionally, they experienced a higher incidence of postoperative pancreatic fistula, delayed gastric emptying, and a greater 90-day mortality rate. The multivariable analysis indicated that several factors were associated with conversion, including lesion size, body mass index (BMI), previous abdominal surgery, patients outside benchmark criteria, and age (>62 years old). The authors emphasized the necessity of proper patient selection through validated difficulty scoring system (DSS).

The laparoscopic approach represented a significant advancement in abdominal surgery by the late 20^th century. While there is no definitive agreement on the exact date of the first laparoscopic distal pancreatectomy (LPD), the most accepted year is 1992. Despite this, the widespread adoption of LPD encountered delays due to the complex anatomy of the pancreas, its proximity to major blood vessels, and the technical challenges associated with the procedure. Although the rates of LPD have been increasing, the growth has been gradual, but now is considered the gold standard (1). But recent studies from various countries over the past 2 years indicate that the current rate of LPD ranges only from 40% to 70% (2).

In 2013, surgeons at the Mayo Clinic performed the first spleen-saving, vessel-preserving RDP using the da Vinci^® surgical system. The robotic technique enhances visualization, minimizes tremor, and improves maneuverability during dissection (3). In the past decade, RDP has gained popularity due advantageous learning curve and theoretical lower conversion rates compared to the laparoscopic approach. An international study conducted across 19 European countries compared LDP with RDP and found no significant differences in outcomes between matched patients, although RDP was associated with a longer operative time (4). Some authors argue that nowadays RDP should be the standard procedure for resecting pancreatic tumors located in the body and tail of the pancreas, rather than LPD (5). The main drawbacks of RDP are the higher costs and challenges in accessing to robot systems.

Conversion is a specific complication of minimally invasive surgery (MIS), including laparoscopic and robotic procedures. As we previously mentioned, there is very little literature available on conversion rates in RDP. Therefore, we will summarize the data regarding conversion in LDP and compare it with the findings from Müller et al. (1).

To begin with, we would like to clarify the term “conversion”. Although there is no universally accepted definition, it is generally understood to refer to performing a laparotomy to complete a procedure. The Brescia Guidelines define conversion as an unplanned open incision, excluding the incision required for specimen extraction, and categorize it into planned and emergency conversions (6). In the case of elective conversions, unexpected intraoperative findings may occur. These can include the infiltration of nearby vessels or organs, difficulties arising from adhesions, challenges in visualizing the tumor, or oncological concerns. In contrast, emergency conversions are often necessary due to uncontrollable bleeding (6-9).

The conversion rate for LDP varies significantly, ranging from 0% to 38% according to published studies (6-10). The rate of Müller et al. is very low, near 3%. Preoperative factors associated with conversion in LDP published studies include male gender, low albumin levels, elevated BMI, smoking, pancreatic cancer, tumors located close to major blood vessels, the type of pancreatic surgery (subtotal vs. distal pancreatectomy), the surgeon’s experience with minimally invasive pancreatic surgery, and the size of the tumor. Conversely, female patients, patients with tumors situated in the tail of the pancreas, and centers that standardize the steps of LDP tend to have lower conversion rates (6-10). Two of these parameters coincide with Müller et al.’s results: lesion size and BMI.

The published series consistently show that patients who experience conversion during surgery tend to have worse outcomes, including higher rates of complications and mortality, as well as increased costs when compared to those whose procedures are completed entirely using a minimally invasive approach. However, there is no agreement on whether conversion is linked to poorer oncological outcomes (6-10).

There are few publications discussing the preoperative determination of conversion risk, including a nomogram and a conversion risk score (CRS) (9,10). Müller et al. used the CRS and showed low discrimination and overestimated the true conversion rate.

To lower the conversion rate in LDP, it is important to understand the difficulty involved in the procedure. Various preoperative classifications evaluate the LDP difficulty, often relying on factors assessed before the surgery. In Japan, a DSS was developed to LDP based on surgical complexity. This system was validated by Goh et al., who implemented some modifications. However, a study validating the Goh-modified DSS at a high-volume European center for pancreatic surgery found that it does not effectively predict the conversion rate (11-13). Defining the difficulty of LDP is complex, as multiple factors can influence it. These include the type of operation, characteristics of the disease, the surgical approach, patient-related factors, technical issues (such as lesion location and the part of the pancreas being resected, whether the neck or tail), and the surgeon’s level of expertise (11-13). By anticipating potentially complex cases, we can facilitate the gradual adoption of minimally invasive techniques and aid in the development of education and training programs for surgeons.

Ramia et al. (14) published a Delphi International Consensus regarding the challenges associated with difficulty in distal pancreatectomy. They identified ten parameters that contribute to these difficulties: previous pancreatic surgery; multivisceral resection; history of acute pancreatitis; tumors located in the neck of the pancreas; chronic pancreatitis; a BMI greater than 30 kg/m²; cirrhosis; previous supramesocolic surgery (excluding cholecystectomy); splenic arterial or venous infiltration; and the preservation of splenic vessels. Clinical validation is required to assess the real-world effectiveness of these criteria in determining surgical difficulty and the likelihood of conversion.

In conclusion, RDP is experiencing significant growth. When performed by experienced surgeons, the conversion rate remains very low. To enhance patient outcomes, it is essential to minimize conversions. To lower the risk of conversion, it is important to identify patients who are at high risk due to the difficulty of their procedures prior to surgery. Open distal pancreatectomy may be a viable approach in such cases.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Gland Surgery. The article has undergone external peer review.

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Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-438/coif). The authors have no conflicts of interest to declare.

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