Can the prophylactic administration of tranexamic acid reduce the blood loss after robotic assisted radical prostatectomy? RARPEX (Robotic Assisted Radical Prostatectomy with TranEXamic acid): study protocol for a randomized controlled trial (SPIRIT Compliant)

The prophylactic administration of tranexamic acid reduces the blood loss during procedures at high risk of perioperative bleeding. Several studies in neurosurgery, cardiac surgery, and orthopedics conrmed this nding. The aim of this prospective, double-blind, randomized study is to evaluate the effect of tranexamic acid on peri-and postoperative blood loss and on the incidence and severity of complications. Based on the results of our pilot study, we decided to conduct this prospective, double-blind, randomized trial to conrm preliminary data. The primary end-point is to analyze the effect of tranexamic acid on perioperative and postoperative blood loss (decrease in hemoglobin levels) in robotic-assisted radical prostatectomy. The secondary end-point is to analyze the effect of tranexamic acid on postoperative complications. Additional end-point is to conrm the safety of tranexamic acid in robotic assisted radical prostatectomy. No study to date has tested the prophylactic administration of tranexamic acid in the of assisted radical This study is designed to answer the question whether it might lower the blood loss after or


Background
Prostate adenocarcinoma is the second most common malignancy in men. The incidence increases over time and with patient age. It is the second most common cause of death due to malignancy in men, after lung cancer. Standard treatment includes radical prostatectomy or radiotherapy in patients with life expectancy more than 10 years (LE1b, GRA) (1-3).
In recent years, there is a general tendency towards minimally invasive surgical procedures. In the treatment of localized prostate cancer, laparoscopic or robotic-assisted radical prostatectomy has become the standard modality of treatment. Despite tremendous development in the technology and technique of robotic-assisted radical prostatectomy over more than 25 years, new ways and methods to improve oncological and functional outcomes are still needed (4)(5)(6)(7)(8).
Decreasing peri-and postoperative blood loss may lead to faster recovery after the procedure (9).
Concerns have been raised about the possible relationship between the administration of blood derivatives and an increased risk of relapse of malignancy and tumor-speci c mortality (10,11).
Tranexamic acid is an anti brinolytic agent used to relieve bleeding. The mechanism of action lies in binding to plasma free plasminogen with higher a nity than tissue plasminogen activator. It prevents its conversion to plasmin, which is responsible for the degradation of brin polymers. It results in greater stability of the brin clot at the site of bleeding and; and therefore lower blood loss (12)(13)(14). The use of tranexamic acid during or after the procedure does not improve results, unlike administration prior to surgery. A biological explanation is that tranexamic acid may bind plasminogen in the early phase of the brinolytic cascade, after the beginning of the procedure, reducing tissue plasminogen activator activity up to 80 % (15).
In urology, increased conversion of plasminogen to plasmin should occur, both by washing the tissue plasminogen activator from the destroyed tissue and by urokinase present in the urine (16). Only few studies have been published to date on the use of tranexamic acid in transurethral prostate resection, open radical prostatectomy, and open radical cystectomy. Several authors did not con rm the positive effect in terms of reduced perioperative and postoperative blood loss in prostate transurethral resection (17). Increasing evidence of the bene cial use of tranexamic acid in cardiac surgery, neurosurgery, traumatology, and orthopedics has led to the renewal of this idea (18)(19)(20). However, newer urological papers continue to produce ambiguous results, from clearly negative (21) to con rmation of the positive effect (22)(23)(24)(25), including a recent meta-analysis (26). Therefore, this trial was conducted in order to clarify this issue.

Methods/design
Objectives and hypothesis The primary aim of the Robotic Assisted Radical Prostatectomy with EXacyl (RARPEX) trial is to investigate the effect of tranexamic acid on perioperative and postoperative blood loss (decrease in hemoglobin levels) in robotic-assisted radical prostatectomy.
H0: The drop of hemoglobin level after the procedure is similar in both groups.
HA: The drop of hemoglobin level after the procedure in control group is higher than in study group.
The secondary aim of the RARPEX trial is to analyze the effect of tranexamic acid on postoperative complications.
H0: The rate of postoperative complications within 90 days after the procedure is similar in both groups.
HA: The rate of postoperative complications within 90 days after the procedure is different between the groups.
Additional end-point of the RARPEX trial is to con rm the safety of tranexamic acid in robotic assisted radical prostatectomy.

Study population and eligibility criteria
All patients who are scheduled for operation due to low or intermediate risk prostate cancer in our institution will be screened and assessed for eligibility.
Only patients who will undergo robotic assisted radical prostatectomy with suturing of dorsal complex vein (DVC) bundle at the beginning of the procedure without pelvic lymph node dissection will be included in the study. Patients with nonstandard procedures or a procedure associated with higher morbidity will be excluded from the study to achieve a homogeneous study group.
Detailed inclusion and exclusion criteria are described below.
Inclusion criteria If subjects do not meet the inclusion criteria or withdraw their consent, they will be excluded from the study. The researcher will record the reason for their withdrawal.

Sample size calculation
The sample size calculation is based on the data from our pilot study (27). We used a Two-Sample T-Tests Allowing Unequal Variance with respect to the primary endpoint, which is the drop of hemoglobin level. With α = 1% and β = 10%, a sample size of 64 patients per group is necessary to detect a clinically signi cant difference between the groups. With an expected dropout rate over 33%, we plan to enroll 200 patients into the study.

Ethics, study registration and consent
This trial was approved by independent ethics committee at the University Hospital Hradec Kralove (registration number 201903 I90P). The RARPEX trial will be conducted in the context of Good Clinical Practice and in accordance with the Declaration of Helsinki. The trial is registered at ClinicalTrials.gov under the registration number NCT04319614. All patients who are scheduled for robotic assisted radical prostatectomy in our institutions will be screened for eligibility and informed in detail about the RARPEX trial. Informed consent will be obtained from each participant. The study procedures, risks, bene ts, and data management will be clari ed with the patients before they are asked to give their informed consent to participate. Any participant in this study may withdraw consent or voluntarily cease to participate at any time for any reason.

Study treatment
Based on the literature and our pilot study (27), we decided to administer a single dose of tranexamic acid, corresponding to 20 mg/kg in 100 ml saline to all patients in the treatment group 1 at the beginning of procedure. In the control group 2 we administer only 100 ml saline as placebo.
For prophylaxis of venous thromboembolism, the combination of mechanical device (graduated compression stockings) and pharmacologic agents (low-molecular-weight-heparin -LMWH) in both treatment groups will be used. The dose LMWH is administered in the evening before the procedure, next dose at least 8 hours after the procedure and then every evening till postoperative day (POD) 7.
Antibiotic prophylaxis is provided by a single dose of potent aminopenicillin as recommended by the antibiotic center; uoroquinolone in patients with an allergy to aminopenicillin. During the procedure, the console time, and weight of prostate is monitored.
The surgical technique is standardized and has been described previously (28). Standard robotic-assisted radical prostatectomy without pelvic lymphadenectomy using DaVinci Xi surgical system is performed. The dorsal vein complex (DVC) is sutured in the beginning of the procedure with two rounds of resorbable mono lament suture. To accelerate the return of continence, a modi ed Rocco stitch is performed in all patients. The anastomosis is performed by two tied V-loc stitches. No additional manipulation, such as brin glue or reinforcement with meshes, is allowed. Patients with rectal or bowel injury during the procedure will be excluded from evaluation.
For three hours after the procedure patients of both groups will stay in intermediate care unit, after moving to standard ward, blood samples will be obtained. On POD 1 all the patients will start with mobilization and solid food intake. The volume of the uids in drain will be measured on postoperative day 1 and if the volume will not exceed 200 ml for 24 hours the drain will be extracted. If the volume is higher than 200 ml / 24 hours and the creatinine level in drain uid exceeds 500 µmol/l, urinary leakage will be con rmed (29).
On POD 2 the patients will be released for home care with indwelling permanent urinary catheter.
On POD 7 the urinary catheter and skin sutures will be extracted and the blood sampling and ultrasound of the lower abdomen will be performed. Three months after the procedure a follow up visit is scheduled.
The evidence of complication and level of prostatic speci c antigen (PSA) is monitored.
Upon completion in 200 patients the statistical processing will be performed, and patients will be unblinded.

Safety aspects
Robotic assisted radical prostatectomy is a highly technically demanding procedure. High-volume surgeons with great experience have better results than low-volume surgeons with less experience (30).
In order to avoid bias based on the learning curve of the surgeons, every surgical procedure will be performed by a senior surgeon who has experience with at least 100 robotic assisted radical prostatectomies. Administration of tranexamic acid at the beginning of the procedure by anesthesiologist is a simple common procedure, performed on a routine basis, and no special training is necessary, and no complications are expected.

Data collection
A daily visit of the study patients will be made by clinical investigators or a delegated physician. All protocol-required information collected during the trial will be entered into the patient's record form.
Preoperative data gathered include patient age, body mass index, American Society of Anesthesiologists physical status classi cation system score and comorbidities. Intraoperative data to be collected include surgery duration (skin to skin), console time (console surgeon activity time), and weight of the prostate.
According to data from our pilot study (27), we are not able to measure perioperative blood loss, because of many biases. The volume of suction uid is affected by urine coming out of open urinary tract, lymphatic secretion from damaged tissue.
Laboratory tests will include blood count and plasmatic creatinine level at the beginning of procedure, 3-6 hours after the procedure, on POD 1, POD 2 and POD 7 in the morning.
The differences between the hemoglobin levels (eventually weighted for the grams of the prostatic tissue) and hemoglobin / creatinine ratios are obtained.
The volume of the uids in drain is measured on postoperative day 1 and if the volume does not exceed 200 ml for 24 hours the drain is extracted. If the volume is higher than 200 ml / 24 hours and creatinine level in the drain uid exceeds 500 µmol/l urinary leakage is con rmed (29). Patient with con rmed urinary leakage or urinoma will be excluded from the evaluation.
Postoperative course assessments will include duration of intermediate / intensive care, hospital stay including readmissions for postoperative complications, reinterventions (reoperations, endoscopy and interventional radiology procedures), the reasons for readmissions and transfusion rates. The patients will be seen by a clinical investigator 3 months after the surgery in the outpatient fashion. The evidence of complication and level of prostatic speci c antigen (PSA) is monitored. Upon completion of 200 patients the statistical processing will be performed, and results will be unblinded.

Primary and secondary endpoints
The primary endpoint is to analyze the effect of tranexamic acid on perioperative and postoperative blood loss -the decrease in hemoglobin levels after robotic-assisted radical prostatectomy. Clinically signi cant difference between treatment groups is set at 10 g/l. We assume that the results will be signi cantly affected by the weight of the prostate. A larger prostate could mean longer operating time and greater blood loss. Therefore, the results are weighted for the grams of the prostatic tissue. Another potential bias could be different hydration of subjects before, during and after the procedure. Therefore, the hemoglobin / creatinine ratio was used.
The secondary aim of the RARPEX trial is to analyze the effect of tranexamic acid on other postoperative complications: wound infection, intraabdominal collections, urinary leakage, delayed gastro-intestinal emptying, postoperative hemorrhage, pneumonia, abdominal rupture (Table 1).
Additional end-point of the RARPEX trial is to con rm the safety of tranexamic acid in robotic assisted radical prostatectomy, especially analyzing the incidence of cardiac events and venous thromboembolism (VTE) after the procedure.  Patients will be randomized to one of groups before the surgical procedure after meeting eligibility criteria. Randomization will be accomplished using balanced permutation blocks by generation of random numbers in order to obtain homogeneity between groups. Opaque, sealed envelopes will be produced, labeled with the randomization number and containing a sheet that states the group allocation for the patient. Randomization envelopes will be used in consecutive order. Basic characteristics of the patient and the day of randomization will be documented on a data sheet so that compliance to the randomization scheme may be checked retrospectively. To maintain the double-blinding, the placebo and active ingredient are identical and cannot be distinguished by appearance by the participants or staff.
The code assigned to subjects will be kept sealed and will not be released until the end of the clinical trial. Cases in which the blinding must be unsealed, such as a serious adverse drug reaction, will be managed using a separate envelope created for each subject so that only their randomization is revealed. Randomization and blinding will not be revealed to the researchers until the end of the study. If patients are excluded from the study after randomization, their numbers will not be reused.
Unblinded nurse will prepare an infusion set according to the information in the sealed envelope with the patient's study number on the day of procedure. For patients in the intervention group 1, the dose of tranexamic acid according to target 20mg/kg will be added to 100 ml of physiological saline. For patients in the intervention group 2 she will add no other substance to 100 ml of physiological saline. Infusion will be given into the sealed envelope, sent to the operating theatre and given within 5 minutes after the robotic system is docked.
Operating surgeons, attending physicians, nursing staff and outcome assessors will be blinded. The randomization process will follow the CONSORT guidelines (32) (Fig. 1).

Minimizing treatment bias
Administration of tranexamic acid at the beginning of the procedure by anesthesiologist is a simple common procedure, performed on a routine basis, which eliminates a learning curve.
All patients will undergo robotic-assisted radical prostatectomy without pelvic lymphadenectomy using the same technique. All surgeons participating in the study are familiar with this procedure. The dorsal vein complex (DVC) will be sutured at the beginning of procedure.

Minimizing measurement bias
Measurement of hemoglobin level drop and detection and grading postoperative complications will be based on data in the patient's record form. Patient and clinical investigators or a delegated physician will be blinded.

Statistical methods
Each patient's allocation to the analyzed population will be de ned prior to the analysis and will be documented. In the full-analysis set, patients will be analyzed as randomized according to the intentionto-treat principle. The intention-to-treat principle implies that the analysis includes all randomized patients. The per-protocol analysis set will include all the patients without major protocol deviation.
Deviations from the protocol will be assessed as major or minor. Patients with major deviations from the protocol will be excluded from the protocol analysis. The safety analysis set will analyze patients according to the treatment. The null hypothesis assumes that there is no difference in the hemoglobin level drop after the procedure in both groups. We will use a Two-Sample T-Tests Allowing Unequal Variance with respect to the endpoint, which is the drop of hemoglobin levels. Differences between age and PSA will be assessed by the nonparametric Mann-Whitney U test. BMI and specimen weight will be compared by the Kolmogorov-Smirnov test. A P-value < 0,05 will be considered statistically signi cant. Statistical analyses will be performed using NCSS statistical software (NCSS, Kaysville, UT, USA).

Discussion
One of the greatest risks of any technical demanding surgical procedure is bleeding. It is similar in radical prostatectomy. The robot-assisted approach leads to a signi cant reduction of blood loss. Nevertheless, efforts to reduce the blood loss even more are eagerly awaited. Perioperative hemorrhage makes the surgical terrain unclear, makes it di cult to dissect the tissue precisely, increases the risk of complications and worsens functional and oncological results. Excellent experience in orthopedics and other cardio-surgical elds with the prophylactic administration of tranexamic acid after the introduction to anesthesia gives rise to the hope of successful use in urology as well. Based on the results of our pilot study, we demonstrated lower blood loss in the tranexamic acid group compared to the placebo group. The differences were statistically signi cant evaluating the decrease in hemoglobin, especially when related per gram of prostate removed (27).
The therapeutic concentration of tranexamic acid in plasma ranges from 5 mg/kg to 10 mg/kg. After an intravenous dose of 10 mg/kg, plasma concentration was maintained for 3 hours, but orthopedics proved to be inadequate. Based on the above-mentioned literature, we decided to administer a single dose, corresponding to 20 mg/kg to all patients in the treatment group 1 at the beginning of procedure.
Radical prostatectomy is associated with a higher risk of thromboembolism. Open radical prostatectomy has a considerably higher risk of thromboembolic events (1.0-15.7%) compared to a robotic (0.2-3.7%) and laparoscopic approach (0.4-6.0%) (34). Administration of anti brinolytics, which potentially increase the risk of thromboembolism in laparoscopic surgery for pelvic malignancy, may seem too risky. According to literature data from a meta-analysis of 11 studies involving 1177 patients with malignancy found no demonstration of an increased risk of thromboembolism following treatment with tranexamic acid (26). Our data from the pilot study correspond with this statement. Despite the enormous development in robot assisted radical prostatectomy over 25 years, improvement is still needed.
One possibility is to implement the ERAS (early recovery after surgery) protocol in everyday practice. Each of the original 22 recommendations (for example, preoperative nutritional examination and nutritional preparation, intestinal preparation, fasting time, prevention of thromboembolism, antibiotic prophylaxis, decolonization of the skin, minimally invasive approach, prevention of hypothermia, intestinal prokinetics, etc.) might signi cantly improve the postoperative results. The prophylactic use of tranexamic acid in the beginning of robotic-assisted prostatectomy could be another method how to improve the results.

Trial Status
The RARPEX trial is recruiting patients under protocol version 1.0 since February 24, 2020. The last patient is expected to be recruited by December 31, 2021.

Declarations
Ethics approval and consent to participate This trial was approved by independent ethics committee at the University Hospital Hradec Kralove (registration number 201903 I90P). The RARPEX trial will be conducted in the context of Good Clinical Practice and in accordance with the Declaration of Helsinki. All patients who are scheduled for robotic assisted radical prostatectomy in our institutions will be screened for eligibility and informed in detail about the RARPEX trial. Informed consent will be obtained from each participant. The study procedures, risks, bene ts, and data management will be clari ed with the patients before they are asked to give their informed consent to participate. Any participant in this study may withdraw consent or voluntarily cease to participate at any time for any reason.

Consent for publication
Not applicable.
Availability of data and materials The materials described in the manuscript, including all relevant raw data, will be freely available to any scientist wishing to use them for non-commercial purposes, without breaching participant con dentiality.
The datasets used and analyzed during the current study will be available from the corresponding author on reasonable request.

Competing interest
The authors declare that they have no competing interests.
Funding wrote most parts of the protocol, he was responsible for study design and revision of the manuscript and he obtained funding. MBr, JP and FC helped with de nition of the primary and secondary endpoints and contributed to study design and to development of the proposal. MBa, JK, PH and MBr will perform the procedures. All authors read and approved the nal manuscript.