Oncologic outcomes of unknown primary squamous cell carcinoma of the head and neck following TORS-based management

Presentation: C057
Topic: Pharynx / Larynx Cancer
Type: Poster
Date: Thursday, April 19, 2018
Session: 9:00 AM - 7:00 PM
Authors: John R Sims, MD, Kathryn M Van Abel, MD, Katharine A Price, MD, Daniel J Ma, MD, Daniel L Price, MD, Eric J Moore, MD
Institution(s): Mayo Clinic

Objective: To determine the oncologic outcomes for patients who undergo primary TORS-based management for unknown primary squamous cell carcinoma (SCC) of the head and neck and no primary is found.

Design: Retrospective review.

Setting: Tertiary care referral center.

Participants: Patients with unknown primary SCC who underwent transoral robotic surgery (TORS)-based evaluation and treatment from 5/2007-5/2016 were reviewed.  All cases in which a primary tumor was ultimately found during initial evaluation were excluded. 

Main Outcome Measures: Locoregional recurrence rates and clinical outcome at last follow-up

Results: A total of 19 patients met criteria (89.5% male; median age 53 years, range: 46-77). Final nodal staging was 15.8% N1, 36.8% N2a, 36.8%  N2b, 5.3% N2c, and 5.3% N3.  Nodal metastases were HPV positive 66.6% (12/18) of tested specimens and HPV negative in 33.3% (6/18).  Early in our experience, some patients underwent exam under anesthesia with biopsies alone, as was the historical standard of care.  Due to the early adoption of transoral surgical investigation of oropharyngeal primary sites, surgical management in this series most commonly included a combination of ipsilateral palatine tonsillectomy (73.7%) and ipsilateral lingual tonsillectomy (68.4%) in addition to select neck dissection (100%).  Most patients received adjuvant radiation (47.4%) or chemoradiation (26.3%).  Radiation most commonly included 60 Gy to the ipsilateral neck, 54 Gy to the contralateral neck if cN0, and 54 Gy to high risk mucosal sites.  For HPV positive disease, this included the oropharynx only, while for HPV negative disease this included all mucosal surfaces from nasopharynx to hypopharynx.  The most common chemotherapy regimen was weekly cisplatin, though most patients did not complete all prescribed chemotherapy.

There were 2 (10.5%) local recurrences at 32 and 39 months, each in the ipsilateral base of tongue which had been only biopsied at the time of primary surgery. There was 1 (5.3%) regional recurrence at 15 months.  All 3 locoregional recurrences had HPV negative nodal metastases and 2 of them underwent surgery alone as primary treatment despite recommendations for additional therapy.  There were no local or regional recurrences in patients with HPV positive nodes.  Overall, 89.5% of patients had no evidence of disease at last follow up with a median follow up of 24 months (IQR 15.3-40.2).

Conclusions:  Overall, patients with primary tumors that remain unknown despite TORS-based management have a low local recurrence rate and oncologic outcomes comparable to patients with known primary tumors.  Risk factors for locoregional failure include HPV negative nodal disease and abstaining from adjuvant treatment.  In HPV positive patients, primary radiation fields can be focused on the oropharynx alone without negative oncologic consequences. This data may help in decision-making and counseling patients with unknown primary SCC at high risk for occult oropharyngeal primary disease.