Robot-assisted Partial Nephrectomy With and Without Mixed Reality (REALITATEM Study)

Kidney cancer has had a raising diagnostic incidence and partial nephrectomy (PN) is the standard of care for renal masses stage cT1a and a possible treatment choice for cT1b/T2; PN may be associated to a variety of tools, such as three-dimensional (3D) models, which can be used as printed models or through VR (virtual reality) and/or AR (augmented reality). Virtual reality is defined as an artificial 3D visual environment and AR, as virtual objects superimposed on the real world; mixed reality (MIXREAL) is the association between VR and AR.

The first clinical experience using AR in a PN was in 2008, and since then, clinical trials of 3D assisted minimally invasive PN have been developed, such as the first trial evaluating both AR and VR in videolaparoscopic PN, a prospective cohort, and the first randomized clinical trial evaluating 3D model in robot assisted PN (RAPN), but using only VR; posteriorly, Porpiglia et al. and Li et al. published clinical trials of RAPN using AR.

The investigators aimed to establish the improvements that use of MIXREAL can provide in perioperatory and functional outcomes of RAPN. Although previous studies have been showing positive results on behalf of 3D virtual models, besides this being the first study in Latin America to employ MIXREAL in minimally invasive PN, it is the first randomized clinical trial to employ both AR and VR in the context of RAPN.

To analyze the efficacy of MIXREAL, the investigators intended to allocate forty-five patients with renal lesions to RAPN with, Realitatem Group (RG), or without, Control Group (CG), use of MIXREAL.

Patient's accrual occurred in the private clinic of a few urologists, and patients were blinded to the intervention they would be submitted to. The randomization process was done in a manual pattern, where the next case would always be enrolled to a different group than the previous, starting the study with a patient enrolled to RG.

Besides sociodemographic data, pre-operative data regarding the tumor also was collected and it was determined by an updated CT, done within one month from the surgery. Patients randomized to RG were specifically required an angioCT. The images were exported in DICOM (Digital Imaging and Communications in Medicine) and applied in Brainlab Elements software (Brainlab AG, Munich, Germany), where the images and 3D drawing were rendered in partnership with the collaborating bioengineer of this work to obtain the VR (Figure 1). Planned cases were available via cloud services for immediate use in the operating room (www.brainlab.com).

All surgeries were robot-assisted, conducted transperitoneally, and executed at Moinhos de Vento Hospital (Porto Alegre, Rio Grande do Sul), a tertiary center, from August 2022 to January 2024 by 8 urologists with experience in RAPN. AG was obtained through the Magic Leap 1 goggle (Magic Leap Inc., Plantation, FL, USA) (Figure 5); the only role Brainlab and Magic Leap industries had in this study was the providing of the software and the goggle free of charge.

Besides tumor and patient's baseline characteristics and intra-operative data, such as vessel clamping, ischemia time, estimated blood loss (EBL), use of hemostatic agents and excision technique, post-operative data, such as renal function, anatomopathology, complication rate and hospital staying, were also recorded. Our primary endpoint was ischemia time and the rest were secondary endpoints.

The results obtained were stored in a confidential database, with exclusive access to the researchers, and later organized in the Statistical Package for the Social Sciences (SPSS), proceeding to statistical analyzes.

Initially, descriptive analyzes were performed to characterize the sample of participants. Later, comparisons were made between GR and GC through non-parametric tests Mann-Whitney, Chi-square (CH2) and, when necessary, Fisher's exact test. These comparisons constituted homogeneity analyzes between the groups in the case of sociodemographic, preoperative and histopathological characteristics, while in the perioperative and functional variables they served to find a possible difference related to whether or not to use MIXREAL. For all analyzes performed, it was adopted the 95% confidence interval and the significance level of 5% (p ≤ .05).

The sample was calculated using the Risk Calc software. Assuming a difference in mean ischemia rate (primary outcome) between treatment groups to be 3.9 minutes (20), an expected population standard deviation to be 3.23 (11) and a clinically relevant difference to be of 1 minute (22), to achieve 80% power (i.e., 1-β=0.8) at the level of significance of 5% (α=0.05) with equal allocation (i.e., k=1) and dropout rate of 5%, a total sample of at least 34 patients, divided into two groups, would be required

Inclusion criteria

• patients above 18 years old with solid renal masses or complex renal cysts Bosniak III/IV requiring partial nephrectomy

Exclusion criteria

• solid renal masses or complex renal cysts Bosniak III/IV with initial indication of radical nephrectomy