Preparing for the Worst: Management and Predictive Factors of Open Conversion During Minimally Invasive Renal Tumor Surgery (UroCCR-135 Study)

Take Home Message The open conversion (OC) rate in minimally invasive surgery for renal tumors is low (1.9%). Only 20% of OC cases occur in a context of acute emergency; others are caused by various situations. Robot-assisted surgery may decrease the probability of OC.


Introduction
Minimally invasive surgery (MIS) for renal cancer is nowadays the standard of treatment for localized tumors, allowing the same oncological control of the disease with better perioperative outcomes than open surgery [1].Nephron sparing surgery is preferred whenever it is judged feasible.MIS for partial nephrectomy (PN), especially robot-assisted PN, has increased worldwide, probably due to the facilities of robotassisted surgery for the trickiest parts of the procedure (enucleation and parenchyma's suture) [2].When radical nephrectomy (RN) is preferred, MIS (laparoscopic or robot assisted) is still favored whenever possible [3].
Open conversion (OC) during MIS is a rare (2-10%) [4] and dreaded complication, especially with robot-assisted surgery when the surgeon is not directly operating on the patient.Since experience of surgeons is increasing regarding MIS [5], and maybe because experimented MIS surgeons feel more comfortable and accurate doing MIS rather than open surgery, OC rate is decreasing over time [4] and is lower in experimented centers [6].
Data regarding OC are reported from big national databases, without precise description of the reasons for OC [7,8].For instance, to the best of our knowledge, no data have ever been published distinguishing OC in a context of relative emergency (elective conversion) versus OC in a context of absolute emergency (emergency conversion).The observed predictive factors of OC were RN, older year of surgery, exclusive laparoscopic approach [9], and tumor complexity [7,8,10].Logically, patients with OC have impaired postoperative outcomes with a higher rehospitalization rate [10].
The objective of the study was then to describe precisely the rate, reasons, and perioperative outcomes of OC in a modern cohort of patients who experienced MIS for renal tumors.The secondary objectives were to find predictive factors of OC.

Study design
This was a retrospective study conducted in the framework of the UroCCR project (French network of research on kid-ney cancer, NCT03293563), which is a French multiinstitutional prospectively maintained database of patients treated for kidney tumors.All patients received oral and written information about the objectives and methodology of the UroCCR project, and their written informed consent was obtained (CNIL authorization number DR-2013-206).

Precisions about surgeries
The selected patients were scheduled for the surgical treatment of renal masses with MIS (which encompassed laparoscopic or robot-assisted PN and RN) and had unplanned OC during the procedure.''Emergency OC'' implied an immediate life-threatening situation not reasonably manageable with MIS (significant not repairable or precarious repaired active bleeding).We defined all other situations as ''elective OC''.

Data measurements
Based on the UroCCR database, we evaluated the clinical characteristics of patients (age, sex, body mass index [BMI], previous abdominal surgery, size, side and complexity of tumor), surgeries, and postoperative outcomes.Each center was contacted to enlighten the context of OC (emergency or elective OC, patient repositioning, type of incision, surgeon's experience, and call of the other senior surgeon) and describe the reason for OC precisely.Intraoperative complications were described using EAUiaiC classification [11], and postoperative complications were described using Clavien-Dindo classification [12].For all analyses, SPSS version 25.0 (IBM Corp., Armonk, NY, USA) and R software environment for statistical computing and graphics (version 3.4.3)was used.All tests were two sided, with a level of significance set at p < 0.05.

3.1.
OC rate and patients characteristics From 2008 to 2022, of a total of 8566 registered MIS procedures in 25 centers, 163 were OC.The incidence rate of OC was 1.9% for all MIS procedures, ranged from 0.2% to 10.2% across centers, and was twice higher for minimally invasive RN (MIRN) than for minimally invasive PN (MIPN): 2.9% for MIRN and 1.4% for MIPN (Supplementary Table 1).
The included patients are summarized in Table 1: 71.2% were male and 39.3% had a BMI of >30 kg/m 2 .The median tumor size was 5.2 cm.The number of OC procedures performed was slightly more in right tumors (55.8%).Fifty-one patients (31.3%) had a history of abdominal surgery.Regarding intraoperative complications according to the EAUiaiC classification, the proportions of patients with grades 2 and 3 are the same as those of the patients with emergency and elective OC (18.8% and 82.2%, respectively).No patients had a grade 4 complication: one had a hemostatic splenectomy and another extensive intestine resection with stoma for ischemic colitis, but during subsequent surgeries.No patient had a grade complication 5 because there was no intraoperative death.However, five patients (3.1%) died within the 90 days after surgery: two because of multiple organ failure due to massive blood loss, two due to complications after peritonitis (anastomotic leakage after colectomy and duodenal diverticulum injury), and one after cardiorespiratory arrest due to severe aspiration pneumonia.
More information regarding intra-and postoperative outcomes according to the degree of emergency of OC and the scheduled surgery is presented in Supplementary Tables 2 and 3. Emergency conversion was more associated with significant bleeding and unplanned conversion from PN to RN than elective conversion, but not with length of stay, surgical reintervention, or death (Supplementary Table 2).OC in case of planned RN occurred more frequently for novice surgeons (Supplementary Table 3).

3.3.
Comparison between patients with and without OC (matched cohort n = 489) In the matched-paired cohort, robot-assisted surgery was less frequent in the OC patients: 42% versus 67% without OC (77.1% vs 93.2% in case of MIPN and 19.5% vs 41.5% in case of MIRN).Patients with OC had a higher median tumor size (5.2 vs 4.5 cm), higher cT stage, and higher renal score.Patients with OC had logically worse perioperative outcomes than patients without OC (Table 4), with significantly

Discussion
Based on our results, OC was a rare situation in MIS for renal tumors (1.9%).Fortunately, emergency OC was even more uncommon (about once every 300 procedures).However, surgeons have to prepare for this situation as concerned patients might have very serious complications and even die during or right after surgery.Our results might enlighten surgeons about various situations than can lead to an OC and help them anticipate this technically demanding surgery as best as they can.
Preoperative planning seems crucial to prevent technical difficulty during the procedure.Careful interpretation of a recent imaging, or even more three-dimensional reconstruction [13,14] might help figure out anatomical boundaries of the tumor and better decide between nephronsparing nephrectomy or RN, and laparoscopic or open surgery.Patient's counseling should be adapted to each situation, detailing advantages, drawbacks, and risks of the planned surgery [15].OC should always be discussed with the patient preoperatively and included in the ''possibles'' during informed consent.An elective OC during MIS due to concerns for oncological control or tumor extension should not be seen as a complication, but rather a judgment call by the surgeon to modify the surgical approach for better patient care.In case of significant active bleeding, OC is not imperative, but appropriate experience in MIS and composure are mandatory to resolve the issue [16], as the surgeon has to be as fast and precise as possible for the vascular control (temporary clamping and effective stitches).Bed-side assistant has a crucial importance in case of robot-assisted surgery, since only he/she can apply clips or clean the surgical field with the suction device.After increasing the pneumoperitoneum, if OC is judged inevitable by the operator, at least bleeding should be decreased (application of accurate pressure with a tonsil swab or vascular clamp) during the critical period of OC.Nontechnical factors, such as communication [17], teamwork (good coordination with the anesthesiologist for hemorrhagic shock and quickly disposable blood products), and decision-making, are also critical to overcome such delicate situations.Call of the other senior surgeon could be particularly useful and was surprisingly underused in our cohort.Implementation of surgical simulation training programs addressing critical situations such as OC [18] could be interesting to be more armed in this exceptional situation, as processed in the aeronautic industry for the management of failures.If done more systematically during initial formation [19], and also periodically for confirmed surgeons, it might prevent inappropriate management of OC, facilitate communication, and increase decision-making.
Regarding intraoperative rates of OC, our results are slightly lower than previous data [4,[7][8][9].This could be explained by a more recent cohort or more experienced surgeons and centers.Some OC might have been missed in our registry if any surgery had been registered falsely as an upfront open surgery in such situations.Another important result of our study is the first reported (to the best of our knowledge) rate of emergency OC: one out of 300 procedures.Furthermore, OC in MIS for renal tumors is more uncommon than in other nonurological surgeries [20,21], attesting than MIS seems particularly appropriate for renal tumors and that urologists have long experience of MIS, especially robot-assisted surgery [22].
Our results are in accordance with previous studies regarding the predictive factors of OC such as obesity [4], nonrobotic approach [7,9], and tumor stage [8].Male sex as a predictive factor was also found by Klein et al [7], but we could not confirm it, since our paired cohort was matched on sex.These factors seem intuitive and underpin that the more difficult the surgery is expected to be, the higher would be the risk of OC.For the prevention of OC, surgeons should certainly take into consideration these factors; however, OC occurred in only 2% of MIS cases and would remain largely uncertain.Thus, intraoperative precautions, such as a large accessible surgical field with palpable anatomical landmarks or a box of open surgical tools in the operative room, could help facilitate OC and decrease its duration.
OC rate was almost twice higher for RN than for PN, and could be explained by a smaller proportion of robot-assisted surgeries during RN [9] and an underestimation of local tumor extension before surgery.In case of tumors planned for PN, unexpected local tumor extension might also be managed by conversion to RN, staying in MIS, without the necessity of OC.However, toxic fat leading to OC was an exclusive PN issue.There are several models that aim to predict adherent perinephric fat [23,24], and their use should be encouraged.Nevertheless, the intraoperative dif- ficulties caused by toxic fat, leading in worst cases to OC, are very hard to anticipate, and widely depend on surgeon's experience and tumor location.
Our study has several limitations: first, detailed reasons and modalities of OC were assessed retrospectively based on operative reports, leading to potential information biases.Second, OC rate could have been underestimated if a surgery had been registered falsely as an upfront open surgery in our multicenter database.Third, the only way to find the predictive factors of OC was to create a paired cohort on the UroCCR database, matched on age, size of tumor, and type of surgery because two groups would really be unbalanced using all the UroCCR patients (thousands of patients).This could have led to a lack of power to detect the predictive factors of OC.

Conclusions
OC was a rare situation in MIS for renal tumors (1.9%), and emergency OC occurred once in every 300 procedures.Increased BMI and cT stage were independent patientrelated predictive factors of OC.Patients concerned by OC might have very serious complications and even die during  or right after surgery.Our results might enlighten surgeons about various situations than can lead to OC, and help them anticipate this event as best as they can.
9) No data 35 (21.5)Previous renal mass biopsy, n (%) 15 (9.2) History of abdominal surgery, n (%) 51 (31.3)ASA = American Society of Anesthesiologists; IQR = interquartile range.E U R O P E A N U R O L O G Y O P E N S C I E N C E 6 3 ( 2 0 2 4 ) 8 9 -9 5 longer length of stay, higher EBL, and more postoperative complications, surgical reinterventions, and death.
values; IQR = interquartile range.E U R O P E A N U R O L O G Y O P E N S C I E N C E 6 3 ( 2 0 2 4 ) 8 9 -9 5 Society of Anesthesiologists; extr = extreme values; IQR = interquartile range.E U R O P E A N U R O L O G Y O P E N S C I E N C E 6 3 ( 2 0 2 4 ) 8 9 -9 5

Table 2 -
Characteristics of surgery

Table 3 -
Detailed reasons of open conversion E U R O P E A N U R O L O G Y O P E N S C I E N C E 6 3 ( 2 0 2 4 ) 8 9 -9 5

Table 4 -
Comparison between patients with or without unplanned open conversion, in a 2:1 paired cohort (matched on age, sex, and type of surgery)