RESULTS Patient Eligibility: • Diagnosis was based on p16 positivity on immunohistochemistry and/or HPV positivity on in situ hybridization. • Patients were mostly treated with concurrent chemoradiation. • Those with PET/CT scans before and after treatment were investigated for RPLN positivity in the official radiology report of their imaging. PET/CT imaging: • RPLN positivity was defined as a lesion measuring 10 mm or larger in the shortest diameter on PET/CT and interpreted as a

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... l node by the radiologist on the imaging report. DISCUSSION This is a unique investigation utilizing PET/CT to classify RPLN status in HPV associated OPSCC. RPLN were a relatively uncommon finding in our HPV associated OPSCC cohort with pre-treatment nodal positivity of 3.4% compared to the quoted positivity of 10-27% for all OPSCC. A combination of PET/CT was found to be useful in identifying RPLN. Furthermore, the lack of an association between RPLN status and outcome was consistent with recent studies showing a diminished prognostic influence of lymph nodes in HPV associated OPSCC. Prospective investigation will be needed to determine the precise impact of RPLN on HPV associated OPSCC treatment and outcomes.