Retropharyngeal lymph node involvement in human papillomavirus-associated oropharyngeal squamous cell carcinoma.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to retrospectively review patients with human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) for the presence of retropharyngeal lymph nodes (RPLNs) prior to treatment using positron emission tomography/computed tomography (PET/CT), and to determine if the presence of RPLNs is of utility in predicting outcomes. STUDY DESIGN: Retrospective review of patient data from a single institution. METHODS: Two hundred thirty patients with a diagnosis of HPV-associated OPSCC were identified from 2002 to 2013. The presence of RPLNs was determined primarily from findings on PET/CT as reviewed in a standardized fashion by two neuroradiologists. RESULTS: Of the 230 patients, 165 had pretreatment PET/CT imaging available for review. There were a total of 16 patients (9.70%) with evidence of RPLNs. Among patients positive for RPLNs pretreatment, with an average follow-up of 2 years, there was a 5.2-times greater odds of having recurrence or death (31.3% vs. 8.1%, P=.004). When T and N stage were adjusted for with multiple regression, there was no significant association between RPLN status and recurrence free survival. CONCLUSIONS: This is a unique investigation utilizing PET/CT to classify RPLN status in HPV-associated OPSCC. RPLNs were relatively common in our HPV-associated OPSCC cohort at 9.70%, at the low end of the quoted positivity of 10% to 27% in all OPSCC. A combination of PET/CT is useful in identifying RPLNs. Prospective investigation will be needed to determine the sensitivity and specificity of PET/CT in identifying RPLNs, and the precise impact of RPLNs on HPV-associated OPSCC treatment and outcomes. LEVEL OF EVIDENCE: 4.