The Utility of Biomarkers in Radiation-Induced Salivary Gland Damage

Abstract

Although radiation therapy aims to target cancer cells, it results in inevitable nearby normal tissue damage. Xerostomia (i.e., dry mouth) is a common complication for patients with head and neck cancer, often caused by salivary gland dysfunction after radiotherapy cessation. The resulting hyposalivation negatively impacts the patients’ quality of life by leading to oral pain, mastication and swallowing difficulties, dental decay, impaired speech, and interrupted sleep schedules. Despite the recent technological advancements in radiotherapy, radiation oncologists still face the challenge of delivering tumoricidal doses while sparing nearby healthy tissues. Future approaches that maximize the therapeutic outcome of radiotherapy rely on assessing the individual’s radiosensitivity before and during the treatment course. Extensive research on biomarkers of radiation injury is in progress to achieve personalized radiotherapy or predict the molecular response to ionizing radiation (IR). The field of biomarkers has shown an accuracy in distinguishing pre- and post- IR states of high dose impact on irradiated tissues. Several studies on body fluid biomarkers showed a promising contribution in predicting and monitoring the disease prognosis and collateral normal tissue injury. The importance of body fluid biomarkers lies in their non-invasiveness, convenience, reflectiveness of tissue biopsy, and ease of multiple collections. In this paper, we summarize current knowledge about radiation-induced toxicity of salivary glands with an overview of the significance of body fluid biomarkers in its detection. Moreover, we pay particular attention to saliva as a potential diagnostic tool for radiation injury of salivary glands.