Prognostic Factors in Oropharyngeal Cancer Treated With Definitive Chemoradiotherapy

HPV-negative oropharyngeal squamous cell cancer (OPSCC) is associated with poor clinical outcomes. The main objective of this study was to evaluate prognostic factors of OPSCC treated with definitive chemoradiotherapy (CTRT).

Consecutive patients of OPSCC treated with definitive CTRT in a tertiary care center from January 2013 to December 2017 were analysed retrospectively. Kaplan-Meier method was used for survival analysis, Log-rank test was used for univariate analysis (UVA), and Cox regression method was used for multivariate analysis (MVA).

Out of 630 eligible patients, 543 (86.1%) had locally advanced stage according to AJCC 7^th edition. HPV status was known for 500 patients, of which 55 (11%) tested p16 positive, reflecting a predominantly HPV-negative cohort. Chemo-radiotherapy was offered to 447 (71%) patients. Intensity-modulated-radiotherapy (IMRT) technique was used for 163 (25.9%) patients. On UVA KPS ≤ 80 (p = 0.001), p16 negative tumours (p < 0.001), T3-T4 stage (p < 0.001), advanced group stage (AJCC 8^th ed.) (p < 0.001), conventional RT technique (p < 0.001), RT dose < 66 Gy EQD2 (p < 0.001) and residual disease after treatment (p < 0.001) were associated with poor Locoregional control (LRC) rates. On MVA p16 negative tumours (HR 3.1 [95% CI 1.8-5.3]), T3-T4 stage (HR 1.6 [95% CI 1.2-2.2]), conventional RT technique (HR 1.6 [95% CI 1.5-2.3]), RT dose < 66 Gy EQD2 (HR 2.2 [95% CI 1.5-3.4]) were independent prognostic factors for poor LRC. These variables were also significant for local control, disease-free free and overall survival.

In this predominantly HPV-negative OPSCC cohort, HPV status, T stage, RT technique, and RT doses > 66 Gy were independent prognostic factors for all outcomes.