# The Role of Salivary Interleukin-6, Interleukin-8, and Epidermal Growth Factor in Radiotherapy Outcomes in Patients With Head and Neck Cancer: A Review of the Literature

## TL;DR

This review explores how salivary cytokines like IL-6, IL-8, and EGF relate to radiotherapy outcomes in head and neck cancer patients.

## Contribution

The paper reviews the potential of salivary cytokines as non-invasive biomarkers for predicting radiotherapy outcomes in head and neck cancer.

## Key findings

- Salivary IL-6 and IL-8 increase post radiotherapy and correlate with worse oral mucositis and toxicity.
- Salivary EGF decreases after radiotherapy and is linked to worse oral mucositis.
- Salivary cytokines may serve as a baseline prognostic tool for treatment outcomes.

## Abstract

Head and neck cancer (HNC) comprises a heterogeneous group of tumors and is a significant malignancy worldwide. Radiotherapy is a treatment option for HNC patients and is known to elevate pre-inflammatory cytokines. However, cytokines in saliva are not widely studied in HNC patients after radiotherapy. The aim of this literature review is to examine the association of the most frequently analyzed salivary cytokines pre- and post radiotherapy in HNC patients, with the outcomes of the treatment. An analytic search was conducted for this literature review on PubMed and Embase databases. Specific combinations of keywords were used, including salivary cytokines, interleukin-6 (IL-6), interleukin-8 (IL-8), epidermal growth factor (EGF), head and neck cancer, and radiotherapy. Several studies showed an increase in salivary IL-6 and IL-8 post treatment. It was associated with worse oral mucositis, severe toxicity, and treatment outcome. Salivary EGF was decreased post radiotherapy in most cases, and was correlated with worse oral mucositis. A minimally invasive technique, such as salivary sampling, could serve as a baseline prognostic tool. Salivary cytokines may predict which patients will develop severe toxicity, severe oral mucositis, or allow earlier prognosis in the radiotherapy course and outcome.