(1) To describe outcomes of retropharyngeal lymph nodes (RPLN) dissection in HPV+ oropharyngeal squamous cell carcinomas (OPSCCs), and 2) to compare the radiographic and pathological findings of RPLNs.
Study Design: Retrospective chart review.
Methods: Chart review was conducted on patients with HPV + OPSCC receiving TORS at an academic tertiary care center from March 2007 to March 2021. Data collected included patient demographics, treatment information, and imaging and pathology findings for RPLNs.
Results: From a total of 837 patients who underwent primary TORS for HPV-associated OPSCC, 53 patients (6.3%) had ipsilateral RPLNs resected as indicated by radiographic assessment [median age 58 (IQR = 51-64), males 44 (83%)]. Only 18/53 (34%) had prior imaging with positive or atypical RPLN. No contralateral dissection of RPLNs were performed. The vast majority (92%) of patients who received RPLN dissection were tonsillar primary tumors, with the following tumor staging: 38 (72%) early T-stage tumors (cT1/T2), 9 (17%) advanced T-stage tumors (cT3/T4), and 5 (9.4%) unable to be assessed. Metastases to RPLNs were found on surgical pathology in 15 (28%) patients, with 5 found to have extranodal extension. Pathologic 7th edition N-stage 2b or greater was associated with pathologic RPLN metastases (OR 12.63, p = 0.002), but was not associated with radiographic RPLN findings. In particular, all non-tonsillar primaries (3 base of tongue, 1 glossotonsillar sulcus) that received RPLN dissection were found to have pathologic RPLN and pN2b or greater. Recurrence in an RPLN occurred in 3 patients with prior RPLN dissection, none of which had positive RPLN at time of initial surgery. Positive or atypical radiographic RPLN during pre-treatment period was predictive of positive pathologic RPLN (sensitivity 0.73, specificity 0.99, LR+ 101, LR- 0.27).
Conclusion: High rates of metastatic disease are found on RPLN dissection for HPV+ OPSCC. The presence of non-tonsillar primaries with positive RPLN suggests that atypical lymphatic spread may be occurring from extensive cervical lymph nodes metastases. Positive or atypical RPLN on diagnostic imaging is a strong predictor of positive pathologic RPLN, but some metastases may be radiographically silent.