A Randomized Pilot Trial of Virtual Reality Surgical Planning for Head and Neck Oncologic Resection

For cases randomized to VRCEP, VR was used for pre-operative surgical planning. Radiographic images (CT or MRI) were uploaded as a DICOM file to Medical Holodeck V1.0 (Zurich, Switzerland), an immersive 360° 3D software that runs on the Oculus Rift VR headset (Meta, Menlo Park, Calif.). This program was selected for its low cost and automated soft tissue segmentation capability, which does not require technicians for optimal use. Software functions included 3D manipulation of segmented rendering of patient imaging, omnidirectional cross-sectional viewing, measuring, cutting, free-hand annotating, masking, and screen capture/recording. Using omnidirectional view, measure, mark, and cut, the surgeon virtually isolated and resected the tumor (Fig. 1).

Following surgical resection, specimens were taken from the operating room to the gross pathology room for 3D scanning (post-resection modeling) and pathological analysis. Specimens were rinsed with water to remove blood contents and dried to reduce visual glare. Specimens were placed on a structured light 3D scanner (EinScan SP, Shining 3D, Hangzhou, China) and serially imaged. Each side of the specimen was scanned individually, resulting in two separate 3D data surfaces. Three-point cross-registration was used to geometrically align both surfaces into a singular 3D model. The resulting meshwork was rendered into a watertight, photorealistic virtual 3D model that was loaded into 3D Slicer for surgeon and pathologist review and marking.

Outcome Measures

Feasibility

Successful VR generation of the imaging-based model pre-operatively, completion of the VR procedure by the surgeon, and generation and markup of the post-resection 3D model were all completed and used to determine if the VRCEP was feasible. The feasibility cutoff was set at 80% completion.

Surgeon assessment

The NASA-TLX survey was administered to evaluate the impact of VR on surgical procedural burden. This is a validated tool designed to measure the subjective workload of a task, with each category scored from 0 to 100 in five-point increments. The measured categories include mental demand, physical demand, temporal demand, effort, performance, and frustration level. Higher scores in each category indicate a higher demand for the task or a lack of success in the task. Scores from all categories were averaged for the total unweighted NASA-TLX score for each case. Scores were compared between SOC and VRCEP.

In addition to the validated NASA-TLX, a post-operative surgeon assessment survey was developed to capture the surgeon’s perspective of the VRCEP. Post-operatively, surgeons in the VRCEP cohort were surveyed on the VR’s helpfulness and impact on pre-operative planning, and any limitations in its use.

Margin events

The margin event score (MES) and margin event rate (MER) were developed as secondary endpoints using the Clinical Trials Transformation Initiative Framework. While this framework is typically designed for qualitative, patient-driven outcomes for digital health technology, we believe it is applicable in the design of the quantitative trial endpoints presented here.

A “margin event” (ME) was defined as defect-driven margins, positive intra-operative frozen section margins, and/or positive final margins. Thus, each case could have a maximum of three possible events. The MES was calculated per case, along with a mean MES per cohort. We also calculated an MER per cohort as the sum of all MEs over the total possible MEs. Defect-driven margins were defined as margins taken at the time of surgery from the defect/tumor bed, rather than the surgical specimen. The standard for our institution is to take margins from the surgical specimen for pathologic analysis when possible. Positive final margins were defined as at least one positive margin at the time of surgery. We did not penalize for intra-operative frozen sections taken for reasons other than margin assessment, such as confirmation of disease or for nerve margins, given the challenges of identifying this on imaging.

Ad hoc margin event analysis

Initially, we did not stratify for cases in which taking specimen-driven margins is not feasible. In certain types of cases, specimen-driven margins are not feasible, and therefore, we considered these as “expected defect-driven margins.” Expected cases include endoscopic laser laryngeal, maxillectomy, or skull base resections. We performed an ad hoc analysis to assess the impact, if any, of non-feasible or expected defect-driven margins on the significance of the findings. For this analysis, we counted a positive ME only for cases considered unexpected and defined this as an “unexpected defect-driven margin” (uDDM).

Post-resection modeling

Post-resection 3D tumor models were constructed as part of the trial assessments. The construction of the models was used as part of the feasibility assessment, but we also conducted surgeon and pathologist markup of margins in an attempt to assess the feasibility of modeling utility. In future studies, we hope to utilize this part of the protocol to assess agreement between providers and effective communication between the services.

Statistical Analysis

Statistical analysis was conducted on SPSS Version 28.0.1.1. Descriptive statistics were calculated for patient demographics, cancer stage, and surgeon. Two-tailed t-tests were used for comparison of overall NASA-TLX scores and subcategory scores between the VRCEP and SOC cohorts and between cancer subsites. Fisher’s exact test was used to compare DDMs, positive frozen margins, positive final margins, and intra-operative change in plan between cohorts. Chi-square was used to compare MER between cohorts. Two-tailed t-tests were used to compare the average MES. Significance was defined as p-value <0.05.

RESULTS

Thirty-nine patients were enrolled between January 2022 and September 2022, with 19 patients assigned to the VRCEP and 20 patients to SOC. Three patients (one randomized to VRCEP and two randomized to SOC) did not undergo the intended intervention due to a change in treatment plan for nonsurgical management: one with chemoradiotherapy, one with radiation, and one opted for palliative care. One VRCEP patient did not undergo the allocated intervention and was therefore excluded from surgeon TLB and margin event analyses. One SOC patient was excluded from the analysis due to meeting the exclusion criteria (benign pathology).

Thirty-four participants with squamous cell carcinoma were included in the per-protocol analysis, with 17 VRCEP and 17 SOC. No differences in demographic, subsite, and T-stage characteristics between groups were identified (p > 0.05) except for a higher proportion of males in the SOC cohort (66.7% versus 33.3%). There were no intra-operative complications or VR-related adverse events. Three VRCEP patients and one SOC patient had reoperation due to post-operative complications: exploration due to thrombosis/hemorrhage (VRCEP), washout due to flap infection (VRCEP), antibiotic and free flap exploration due to delirium (VRCEP), and reoperation for margins due to specimen fragmentation (SOC).

Impact of VR Case Enhancement Protocol

Feasibility