Introduction: Human papillomavirus Virus (HPV)-associated oropharyngeal squamous cell carcinoma (OSCC) has increased in incidence in recent decades and represents a heterogeneous disease entity in the context of Head and Neck Squamous Cell Carcinoma (HNSCC), in terms of disease prognosis. Treatment of locoregionally advanced OSCC is mainly based on concurrent chemoradiotherapy. Given the younger age of patients, if compared with HPV-negative counterparts, and the high cure rates, the acute- and long-term toxicity in survivors represents a field of interest. However, patient selection for de-escalation trials remains a major challenge due to the lack of robust validated prognostic indicators within the HPV-associated OSCC.Discussion: The impact of smoking status on HPV-associated OSCC prognosis has been demonstrated in the majority of studies. However, the magnitude of the association is unclear due to variability in smoking metrics and study outcomes. Smoking status has been identified as a potential confounding factor in HPV-positive de-escalation trials. Smokers with HPV-positive OSCC have a worse prognosis in most studies than non-smokers and may require different and more aggressive therapeutic strategies.

Treatment of locally advanced head and neck carcinoma not amenable for surgical resection or resected with high-risk features is usually based on (chemo-)radiation treatment. Oral mucositis represents one of the main side effects of (chemo-)radiation, with an important impact on quality of life and causing approximately 20% of early interruption of treatment, leading to a suboptimal dose administered. Treatment and prevention of oral mucositis have a central role in the therapeutic pathways of head and neck cancer patients but remains quite challenging. Although extensive research is conducted to identify interventions for the management of mucositis, very few interventions had sufficient evidence to generate an international expert consensus. This may be partially explained by confounding factors that could influence the development and assessment of oral mucositis. Little is known about the confounding factors of oral mucositis, which, if not well balanced in an experimental study, could lead to non-solid results. The current paper aims to review the main oral mucositis confounding factors related to head and neck cancer patients.