Abstract 17: Patterns of neck nodal metastases and recurrence in human papilloma virus-associated oropharyngeal squamous cell carcinoma after neck dissection

Background: The aim of this study is to address the paucity of data on the potentially unique patterns of neck nodal metastases in HPV-positive oropharyngeal squamous cell carcinoma (HPV+OPSCC). Methods: The neck dissection (ND) specimens of varying levels of HPV+OPSCC patients at University of California-San Francisco from 2010-2016 were reviewed for the numbers and frequencies of clinically evident and occult nodes by neck level, and for those with extra-capsular spread (ECS). Smoking history (>10 pack-years), T status, and local, regional and distal recurrences were also assessed for possible associations with nodal metastatic behavior. Results: Sixty HPV+OPSCC patients underwent primary site trans-oral robotic surgery and 65 NDs, of which 21 (32%) were elective. Forty-three (65%) NDs were in non-smokers. Overall, the mean number of positive nodes per ND was 2.5 (range 1-9). The frequencies of at least one pathologically positive node for neck levels 1b, 2, 2a, 2b, 3, 4, and 5 were 0% (0/41), 67.7% (44/65), 43% (23/53), 13% (7/53), 27.7% (18/65), 7% (4/54), and 8% (2/23), respectively. All positive level 5 positive nodes were clinically evident preoperatively. Five of 21 (24%) elective NDs had occult disease only in levels 2A, 2B, and 3, with a mean number of positive nodes of 1.8 (range 1-3). Three of 21 (14%) elective NDs had nodes with ECS. Six of 44 (13%) therapeutic NDs had occult nodes outside the known preoperative distribution in levels 2b, 3 and 4. There were no occult 2a nodes. Smoking history, primary site, and T status were not statistically significantly associated with a differing metastatic nodal behavior. Twenty-three of 60 and 18 of 60 patients underwent adjuvant radiation and adjuvant chemoradiation, respectively. Thirteen of the 19 patients who only underwent surgery had positive lymph nodes, of which five had N1 disease and four had N2b disease. All four of N2b disease patients refused adjuvant therapy and none have had a recurrence as of follow-up (mean 28 months, range 3-51). The overall mean follow-up was 29.1 months (range 2-76 months), with 72% of patients having at least 12 months. One of 65 (1.5%) NDs developed a neck recurrence in the skin overlying level 2 in a patient in the therapeutic ND cohort who had undergone chemoradiation for ECS. No undissected neck levels developed metastatic nodal disease. Two of 60 (3%) patients developed local recurrence. No patients developed distant metastases. One patient in the cohort died of an unrelated cause. There have been no cancer-related deaths. Conclusions: For HPV+OPSCC, therapeutic NDs should encompass any levels bearing suspicious nodes and levels 2a, 2b, 3, and 4, while elective NDs should be performed and encompass at least levels 2a, 2b, and 3. ECS may be present in occult nodes. For HPV+OPSCC, these selective ND plans, followed by the indicated adjuvant treatment, is associated with a low neck recurrence rate. Citation Format: Madeleine P. Strohl, Steven J. Wang, Patrick K. Ha, Jonathan R. George, Chase M. Heaton, Ivan H. El-Sayed, Jon Mallen St Clair, William R. Ryan. Patterns of neck nodal metastases and recurrence in human papilloma virus-associated oropharyngeal squamous cell carcinoma after neck dissection [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr 17.