Retropharyngeal lymph node dissection in oropharyngeal cancer treated with transoral robotic surgery.

OBJECTIVES/HYPOTHESIS Assess the role of retropharyngeal lymph node dissection in oropharyngeal squamous cell carcinoma treated with transoral robotic surgery (TORS). STUDY DESIGN Prospective case series. METHODS Retrospective analysis of 72 patients with oropharyngeal squamous carcinoma treated with transoral oropharyngectomy, neck dissection, and retropharyngeal node dissection. RESULTS Eight of 55 (14.5%) patients with tonsil primaries had retropharyngeal metastases in contrast to none with tongue base primaries. The presence of pathologically positive retropharyngeal nodes was associated with clinical tumor (T) (P=.002) and node (N) stage (P=.007), preoperative computed tomography (CT) (P<.001), and positron emission tomography (PET)-CT scan (P<.001). The negative predictive value of early T (Tx,1-2) and N stage (N0-N2a) was 91.7% and 100%, respectively. Preoperative CT and PET-CT both yielded a positive predictive value of 100%, while the negative predictive value of imaging was optimized to 95.3% when these modalities were combined. CONCLUSIONS In patients with tonsil cancer the risk of retropharyngeal metastases is negligible in the presence of clinically T1-2, N0-N2a disease and negative CT and PET-CT. We estimate that 40% of patients meet these criteria and may safely forego treatment of the retropharyngeal nodes. Approximately 10% of patients will have positive imaging and we recommend retropharyngeal node dissection at the time of surgery to treat macroscopic disease. In the remaining patients at risk for retropharyngeal node involvement, adjuvant radiotherapy is generally indicated based on other adverse features, and these nodes may be incorporated into the treatment field.