Feasibility of 3D ultrasound for intraoperative tumor margin assessment in transoral robotic surgery for oropharyngeal squamous cell carcinoma: A pilot study

INTRODUCTION: Close margins after transoral robotic surgery (TORS) in oropharyngeal squamous cell carcinoma (OPSCC) are common due to narrow anatomical boundaries, requiring additional radiotherapy treatment (RT). Ultrasound (US) can be used intraoperatively to distinguish tumors from healthy tissue. Our objective was to explore ex vivo US of surgical specimens from OPSCCs using a novel 3D US method to correlate tumor and margin measurements with histopathology.

METHODS: Patients with OPSCC undergoing TORS either primarily or as salvage surgery were included. Ex vivo US was performed immediately after resection in the operation room and 3D US models were obtained. The US images were then analyzed by four surgeons blinded to histopathology for correlation analyses. The accuracy to classify close or free margins using a 2 mm threshold was computed.

RESULTS: Nine patients with OPSCC were included (median age 63 years, six males, five with previous RT, and five were Human Papillomavirus-positive). US and histopathology had a high correlation for tumor (r = 0.84-0.85) and margin measurements (r = 0.76-0.78). US measured deep margins with a mean difference of 0.5 mm (SD: 1.2 mm) compared to histopathology and had 80% sensitivity to detect areas of the surgical specimens with close margins (<2 mm). US correctly categorized the deep margin status in 89% of the surgical specimens, compared to 44% for the lateral margins.

CONCLUSIONS: This proof-of-concept study shows that ex vivo 3D US is feasible for intraoperative evaluation of deep surgical margins during TORS of OPSCCs.