Prognostic Factors for Adjuvant Therapy after Trans-Oral Robotic Surgery in Patients with Oropharyngeal Squamous Cell Carcinoma

Abstract

To identify predictors of adjuvant therapy after Trans-Oral Robotic Surgery (TORS) for Oropharyngeal Squamous Cell Carcinoma (OPSCC). We used the National Cancer Database (NCDB) registry to identify patients with newly diagnosed clinical (AJCC 7th edition) T1-T4 N0-N3 OPSCC treated with TORS between 2010 and 2016. Exclusion criteria were patients with metastatic disease (n = 1,997), biopsy only disease (n = 227), unknown stage (n = 771), and unknown surgical margin status (n = 78). A multivariable logistic regression was performed to determine predictors of adjuvant chemotherapy use after TORS. Variables included in the multivariable analysis include T stage, N stage, HPV status, margin status, performance status, age, case year surgery was performed (2010-2013 vs 2014-2016), and case volume. Case volume was divided into quintiles to assess the impact of case volume per institution with need for adjuvant therapy. Kaplan Meier Survival analysis was used to estimate overall survival (OS). We identified 3,337 patients who underwent TORS between 2010-2016. 3,232 patients (95.03%) underwent a lymph node dissection and the median number of lymph nodes removed was 31. 82.0% of patients were HPV positive and 18.0% were HPV negative. 2,940 patients (88%) were T1/T2 and 397 patients (12%) were T3/T4. Only 44 patients (1.3%) had N3 disease. The percentage of patients with positive and negative margins was 14.9% and 86.1% percent, respectively. The 5-year OS for the entire cohort was 80.8%. The 5-year OS for the HPV+ versus HPV- cohort was 85.2% and 63.5%, respectively (log-rank, p<0.001). Of all patients who received TORS, 1,166 (35.6%) received no further adjuvant therapy, 1,088 (33.2%) received adjuvant RT alone and 1,022 (31.2%) received adjuvant chemotherapy in addition to radiation. Among patients with only T1-T2 disease (n = 3050), 929 (29.6%) required adjuvant chemoradiation. For patients treated at institutions with the highest quintile for case volume, 27.2% required adjuvant radiotherapy and 35.0% required adjuvant chemotherapy. On multivariable logistic regression, patients with higher T stage (OR: 1.28, p<0.001), N stage (OR: 2.32, p<0.001), and positive margins (OR:1.64, p<0.001) were more likely to receive adjuvant chemotherapy. Patients who were treated between 2014-2016 were less likely to receive adjuvant chemotherapy compared to those treated between 2010-2013 (OR: 0.80, p = 0.029). The utilization of adjuvant therapy after TORS remains high, even in high volume centers, which suggests better patient selection is needed to identify a subset of patients that can be treated with TORS alone and undergo treatment de-escalation.