Xerostomia — Chronic Dry Mouth Caused by Cancer Treatment

Xerostomia arises when cancer treatments directly damage or inflame salivary gland tissue—specifically the parotid, submandibular, and sublingual glands. Radiation beams passing through these structures can cause acute inflammation, acinar cell depletion, and progressive fibrosis, leading to a marked decrease in saliva volume and an increase in saliva viscosity.

Saliva is essential for maintaining oral homeostasis, lubricating food, initiating carbohydrate digestion, neutralising acidic substances, and controlling microbial proliferation. When saliva production drops substantially, patients face an elevated risk of rapid dental decay, oral candidiasis, mucosal ulceration, dysgeusia (taste disturbance), and dysphagia (difficulty swallowing).

Uncontrolled dry mouth can dramatically erode quality of life during and after cancer therapy. Difficulty chewing and swallowing often leads to reduced food intake, unintentional weight loss, and malnutrition. Furthermore, the absence of protective saliva exposes teeth to accelerated decay and gum infections, making proactive oral health management an essential priority for preserving function and wellbeing.

Xerostomia is primarily diagnosed through clinical evaluation, patient-reported symptom scales, and physical examination of the oral mucosa. Objective measurement can involve sialometry, which quantifies unstimulated and stimulated saliva flow rates. While not tied to tumour biomarkers, pre-treatment dental evaluations and panoramic radiographs are standard to identify vulnerable teeth before radiation begins.

Xerostomia is most common and severe in individuals receiving external beam radiotherapy for head and neck cancers, including tumours of the oropharynx, nasopharynx, oral cavity, larynx, and salivary glands. It can also occur in patients receiving radioactive iodine for thyroid cancer, those undergoing total body irradiation prior to stem cell transplantation, or those taking certain chemotherapy and supportive medications.

Managing xerostomia combines preventive planning and symptom relief. Modern radiation techniques, such as intensity-modulated radiotherapy (IMRT), are planned to spare salivary glands wherever possible. Active management includes frequent water sips, saliva substitutes, oral lubricating gels, prescription secretagogues (such as pilocarpine), and rigorous dental prophylaxis with high-concentration fluoride gels.