Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
BACKGROUND: Surgical margins play a crucial role in disease prognosis and guidance of adjuvant treatment for patients with head and neck cancer. The definition of clear and close margins in oropharyngeal cancer is debated but can range from 1-5 mm based on HPV status. Examination of gross margins, or the macroscopic distance between visible tumor and the specimen edge, guides sites of intraoperative margin sampling. Given the importance of the gross examination of the resected specimen, the purpose of this study is to examine discrepancies in macroscopic gross versus microscopic margin distances.
METHODS: A multi-institutional retrospective review of patients with p16-positive OPSCC who underwent primary surgical resection via transoral robotic surgery (TORS) between March 2010 to June 2024 was conducted. Gross and microscopic margin data was collected in addition to basic patient demographic and clinical information. Patients with history of radiation therapy and those who did not have both gross and microscopic margin distances available in the final pathology report were excluded. A Wilcoxon signed-rank test was used to assess differences between closest gross and microscopic margin in each specimen. Patients were divided into three cohorts: closest gross margin less than microscopic margin, closest gross margin equal to microscopic margin, and closest gross margin greater than microscopic margin. Impact of confounding variables was assessed in the closest gross margin greater than microscopic margin cohort using a multivariate linear regression model.
RESULTS: The patient cohort comprised 225 patients. Anatomic subsites included 139 patients with tonsil primary and 86 patients with base of tongue primary. The mean closest gross margin was 3.1 mm (range 0.0 – 40.0). The mean closest microscopic margin (among those reported in the final pathology report) was 2.5 mm (range 0.0 – 15.0). In 74 patients (32.8%), gross margins were less than microscopic margins; the mean difference between margins was 2.1 mm (range 0.1 – 13.1) (p < 0.001). In 78 patients (34.7%), gross margins and microscopic margins were equal. In 73 patients (32.4%), gross margins were greater than microscopic margins; the mean difference between margins was 3.7 mm (range 0.5 – 33.0) (p < 0.001). Smaller tumor size was associated with underestimation of microscopic margins (OR 0.37, 95% CI 0.17 – 0.80) controlling for age, smoking history, and tumor subsite. Twenty-one patients had positive microscopic margins (0.0 mm). In these patients, closest gross margins were 0.0 mm in 11 patients, 0.5 mm in 4 patients, 1.0 mm in 2 patients, 2.0 mm in 2 patients, 5.0 mm in one patient, and 8.0 mm in one patient.
RELEVANCE AND CONCLUSION: In patients who undergo TORS for p16-positive OPSCC, gross margins often do not accurately predict microscopic margins. The gross margin can either be an overestimate or underestimate of the actual microscopic margin though the final margin is unlikely to be positive for gross margins 3 mm or greater.