BACKGROUND: The purpose of this study was to investigate if FDG uptake metrics in primary tumor and lymph node metastases in patients with oropharyngeal squamous cell carcinoma (OPSCC) has a prognostic value beyond UICC8 staging in a multiple endpoint model.

METHODS: Patients with OPSCC treated with primary radiotherapy at Rigshospitalet in the period 2010-2017 were included. All patients had a pretreatment FDG PET/CT scan performed. Four cause-specific Cox regression models were built for the hazard ratios (HR) of recurrence in T-, N-, M-site, and death with no evidence of disease (NED), respectively. The following variables were included: T-, N-stage, p16 status, metabolic tumor volume, and FDG uptake in both primary tumor and lymph nodes. A competing risk analysis was performed and absolute risk estimates were estimated using the Aalen-Johansen method.

RESULTS: Overall, 441 patients were included. Thirty-four patients had T-site recurrence, 31 N-site recurrence, 32 M-site recurrence, and 52 patients had death NED as event. Nodal FDG uptake had a significant impact on N- and M-site recurrence, with HRs of 2.13 (CI 1.20-3.77) and 2.18 (CI 1.16-4.10). The individual prognostication of absolute risk of the four events for any given patient can be assessed in the online tool (https://rasmussen.shinyapps.io/OPSCCmodelFDG_PET/).

CONCLUSION: High nodal FDG uptake increases the risk of N- and M-site recurrence in patients with OPSCC in a competing risk scenario. The reported results are available in an easy applicable online tool and can help identify relevant candidates for future trials testing treatment approaches.