Abstract
Background: With the growing interest in treatment de-intensification trials for human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPC), prognostic models have become essential for patient selection. The aim of this paper is to validate and compare the prognostic ability of the TNM 8th edition and previous published risk group classifications of Ang et al. and Rietbergen et al. and to derive a patient selection classification for de-intensification trials.Materials: Patients with HPV+ OPC treated with curative (chemo)radiotherapy between 2004 and 2017 were classified according to the TNM 8th edition, the model of Ang et al. and of Rietbergen et al. HPV status was determined by p16 immunohistochemistry staining. Overall survival was estimated using the Kaplan-Meier method and groups were compared using the log-rank test. Harrell's C-index was used as measure of discriminative performance.Results: A total of 333 OPC were identified of whom 100 were HPV+. The median follow-up was 63.7 months. The 5-year overall survival (5Y-OS) of stage I, II and III were 91.6, 55.2, and 38.0%. There was a significant difference between stage I vs. II and III. The Harrell's C-index for TNM 8th edition stage was 0.67. Including only HPV+ OPC, the Harrell's C-index for the model of Ang and Rietbergen were both 0.62. We combined the main prognostic factors defining the low risk groups in the three models, stage I, low comorbidity and ≤ 10 pack years, into one new low risk group to identify patients who may benefit from de-intensification trials. Intermediate risk was defined as stage I with high comorbidity or >10 pack years, high risk as stage II-III. The 5Y-OS were 100, 85.7, and 51.3%. The Harrell's C-index for the new classification model was 0.67.Conclusion: Although TNM 8th edition provides better OS stratification than the 7th edition, it is not performant enough for patient selection, neither are the models from Ang et al. and Rietbergen et al. Therefore, we propose a patient selection classification for de-intensification trials based on the new TNM classification 8th edition, comorbidity and smoking pack years. In addition, this study emphasizes the importance of patient selection and personalized treatment for HPV+OPC.
Highlights
Due to a change in etiology, oropharyngeal squamous cell carcinoma (OPC) is nowadays the shared name of two distinct clinical entities
We propose a new risk group classification system based on the prognostic factors for Human Papillomavirus (HPV)+ OPC in the three validated prognostic models: tumor stage 8th edition (8th Ed), comorbidity (ACE27 0–1 vs. 2–3) and smoking (≤ of > than 10 pack years) (Figure 10)
We report the validation of the cTNM 8th Ed for HPV+ OPC in our single center Belgian population treated with primaryradiotherapy
Summary
Due to a change in etiology, oropharyngeal squamous cell carcinoma (OPC) is nowadays the shared name of two distinct clinical entities. The incidence of HPV-driven OPC ( called HPV positive (HPV+) OPC) is on the rise, even to that extent that OPC is the only HNSCC subsite with a rising incidence and epidemiologic evidence has shown that it is getting epidemic proportions [2] The prognosis of these two types of OPC is completely different. HPV+ OPC were often diagnosed as a stage III or IV [TNM 7th edition (7th Ed)] since they frequently present as a small primary tumor with multiple cervical lymph nodes Such a stage IV (7th Ed) OPC had a 5-year overall survival (OS) around 70% in contrast to a 5-year OS of 30% for stage IV HPV− OPC [3]. With the growing interest in treatment de-intensification trials for human papillomavirus positive (HPV+) oropharyngeal squamous cell carcinoma (OPC), prognostic models have become essential for patient selection. Harrell’s C-index was used as measure of discriminative performance
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