Prospective Evaluation of Pre-Operative MRI on Margin Status for Transoral Robotic Surgery for HPV+ Tonsillar Squamous Cell Carcinoma

There has been a marked increase in the incidence on oropharyngeal SCC in recent decades because of the rise of HPV+ disease1-3. Stage I or II tonsillar SCC can be treated by either surgery or radiation with similar good outcomes. For tumors treated surgically, transoral robotic surgery has replaced open surgery due to decreased morbidity and improved local control. It has been shown that margin status of 1.1mm of healthy tissue around the tumor is sufficient for adequate local control. However, approximately 8.1% of the time there is a positive or insecure margin, resulting in added adjuvant radiation and possibly chemotherapy, with increasing morbidity for each added treatment modality.

Therefore, there is a need to determine pre-operatively the chance of positive or insecure margin at surgery to avoid increased morbidity with added adjuvant treatment. Currently, the most commonly used imaging modality is computed tomography (CT) or magnetic resonance imaging (MRI), but this is to rule out absolute contraindications such as internal carotid artery encasement, involvement of the mandibular periosteum, prevertebral fascia/musculature, or masticator space musculature. Recently, a retrospective study used a novel five-point grading scale (1, normal constrictor; 2, bulging constrictor; 3, thinning constrictor; 4, obscured constrictor; and 5, tumor protrusion into the parapharyngeal fat) to evaluate the pharyngeal constrictor muscle, showing that higher scores with obscured constrictor or tumor protrusion into the parapharyngeal fat resulted in increased risk of positive or insecure margin. Given this, there is need for a prospective study to estimate the accuracy of the five-point MRI score with respect to distinguishing patients who go onto have secure surgical margins versus patients who go on to have insecure/positive surgical margins including surgical report of violation of anatomic boundaries (pharyngeal constrictor muscle)