The Prognostic Value of Baseline 18F-FDG PET/CT in Human Papillomavirus-Positive Versus Human Papillomavirus-Negative Patients with Oropharyngeal Cancer

Purpose:

Oropharynx cancer (OPC) is heterogeneous; human papillomavirus (HPV)-positive and HPV- tumors represent 2 disease entities with a different prognosis. Earlier studies investigating the prognostic value of pretreatment 18F-FDG PET in OPC are small or included patients with unknown HPV status. This study assessed the prognostic value of PET variables, in a large cohort with balanced HPV status. 

Methods: 

Retrospectively, primary tumor SUVmax, SUVpeak, metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were extracted from baseline FDG PET/CT of patients with OPC treated with (chemo)radiation. The Pearson correlation between the PET variables was calculated. With linear regression, the correlation between the PET variables and HPV status, age, smoking status, T stage, N stage, and American Joint Committee on Cancer stage was calculated. Univariable and multivariable Cox models analyzed local control, overall survival, and disease-free survival (DFS). 

Results:

Of 201 patients, 109 were HPV+. Metabolic tumor volume and TLG correlated (r = 0.96), as did SUVpeak and SUVmax (r = 0.97). The PET variables correlated strongest with HPV status and T stage. These two accounted for 40% of the variance of MTV and 33% of TLG. Human papillomavirus-negative tumors had a significantly higher SUVmax, SUVpeak, MTV, and TLG. In univariable analysis, all PET variables were significantly associated with local control, overall survival, and DFS. In multivariable analysis, TLG was significantly associated to DFS in patients with HPV- OPC (hazard ratio, 1.005; 95% confidence interval, 1.001-1.010; P = 0.03). However, we did not observe this in HPV+ patients. 

Conclusions: 

Increased baseline TLG is associated with worse DFS in HPV- OPC and might be used as biomarker for risk stratification in these patients. Interestingly, we could not identify this association in HPV+ patients.