Understanding approaches to measurement and impact of depth of invasion of oral cavity cancers: A survey of American Head and Neck Society Membership.

OBJECTIVES:To investigate methods used by head and neck surgeons to pre-operatively measure depth of invasion (DOI) in light of the new staging for oral cavity squamous cell carcinoma (OCSCC). MATERIALS AND METHODS:A survey was designed and sent to all American Head and Neck Society (AHNS) members via an email link. The last response was recorded on January 16, 2019. RESULTS:We received 185 (13.3%) responses from 184 surgeons and 1 radiation oncologist. The majority of surgeons correctly identified DOI (78.9%) and indicated measuring DOI pre-operatively (86%). The most common methods for measuring DOI were manual palpation (32.5%) and full thickness biopsy (25.2%). In addition, most surgeons (84.7%) reported using a DOI threshold (in mm) as their primary criterion in their decision to pursue a neck dissection in the N0 neck. The most common reported threshold was 4 mm (37.4% of those that reported using DOI), however, the range varied from 2 to >10 mm. Two-thirds of surgeons considered DOI an important indicator for adjuvant therapy. CONCLUSION:DOI is believed to be an important prognostic indicator guiding neck dissection and the need for adjuvant therapy. While most surgeons currently measure DOI pre-operatively, most use subjective methods. Future studies are needed to establish objective pre-operative DOI measurement techniques and to better inform the decision to perform prophylactic neck dissection, given the current majority practice of prophylactic neck dissection for DOI of 4 mm or greater.