Salivary proteome changes during radiation therapy in patients with head and neck cancer: an exploratory pilot study

Background Oral mucositis is a common complication in patients with head and neck cancer undergoing radiation therapy, often associated with pain, dysphagia, weight loss and hospitalization. Molecular and inflammatory activity underlying oral mucositis has been shown to peak at radiation therapy doses of 51–60 Gy. Saliva is a non-invasive biofluid that reflects local oral and systemic inflammatory processes; however, reliable salivary markers for monitoring radiation therapy-induced toxicity are still lacking. The aim of this exploratory study was to characterize salivary molecular responses to radiation therapy in patients with head and neck cancer and to investigate how these changes evolve during the radiation therapy trajectory in relation to oral mucositis, pain and quality of life. Methods Stimulated whole saliva was collected from nine patients with head and neck cancer at baseline, during radiation therapy, and 12 weeks post-radiation therapy, and from ten cancer-free controls. Salivary proteins were analysed using a combination of untargeted two-dimensional gel electrophoresis and targeted multiplex immunoassays. Multivariate data analysis was applied to identify treatment-related molecular changes. Results At baseline, patients differed significantly from controls at the proteome level without corresponding cytokine changes. During radiation therapy, pronounced changes in both the salivary proteome and cytokine/chemokine profile were observed, alongside increases in mucositis severity and pain intensity and a reduction in quality of life. Proteins involved in salivary gland function and mucosal immunity, including S100-A9, zinc-α2-glycoprotein and α-amylase contributed to the discrimination between baseline and during radiation therapy samples. The cytokine/chemokine profile showed increased levels of several inflammatory mediators, including IL-1β, TNF-α, IL-8 and IL-6. Despite improvement in mucositis severity, pain intensity, and quality of life at 12 weeks post-radiation therapy, both proteome and cytokine alterations remained evident. Conclusions Radiation therapy induces dynamic and sustained alterations in the salivary proteome and cytokine profile in patients with head and neck cancer. These findings suggest that saliva may serve as a non-invasive medium for monitoring treatment-related biological responses during and after RT and guiding supportive care. However, the findings should be considered exploratory due to the small sample size and require validation in larger cohorts.