The Number of Radiographically Positive Lymph Nodes Further Stratifies Patient Survival Among Clinical N1 Patients With Human Papillomavirus-Associated Oropharyngeal Cancer.

Purpose: Human papillomavirus-associated oropharyngeal squamous cell carcinoma (HPV[+]OPSCC) requires further study to optimize the existing clinical staging system and guide treatment selection. We hypothesize that incorporation of the number of radiographically positive lymph nodes will further stratify patients with clinical N1 (cN1) HPV(+)OPSCC. Methods and Materials: A post hoc analysis from 2 prospective clinical trials at a high-volume referral center was conducted. Patients underwent primary tumor resection and lymphadenectomy, followed by either standard-of-care radiation therapy (60 Gy in 30 fractions) with or without cisplatin (40 mg/m2 weekly) or de-escalated radiation therapy (30 Gy in 20 twice-daily fractions) with concomitant 15 mg/m2 docetaxel once weekly. Imaging studies were independently reviewed by a blinded neuroradiologist classifying radiographic extranodal extension (rENE) and the number and maximal size of involved lymph nodes. Patients without pathologic data available for assessment were excluded. Results: A total of 260 patients were included. Of these, 216 (83%) were cN1. Patients had a median of 2 radiographically positive lymph nodes (range, 0-12), and 107 (41%) had rENE. For cN1 patients, stratifying by radiographically positive lymph nodes (1-2 vs 3-4 vs >4) was predictive of progression-free survival (PFS) (P = .017), with 2-year PFS rates of 96%, 88%, and 81%, respectively. More than 2 radiographically positive lymph nodes was identified as a significant threshold for PFS (P = .0055) and overall survival (P = .029). Radiographic ENE and lymph node size were not predictive of PFS among cN1 patients. Conclusions: The number of radiographically positive lymph nodes is predictive of PFS and overall survival and could be used to meaningfully subcategorize cN1 patients with HPV(+)OPSCC. We recommend further validation of our proposal that cN1 patients with 1 to 2 radiologically positive lymph nodes be categorized as cN1a, patients with 3 to 4 radiologically positive lymph nodes categorized as cN1b, and patients with >4 radiographically positive lymph nodes categorized as cN1c.