What causes dry mouth in cancer? How is it treated?

What is dry mouth, medically called xerostomia?

Xerostomia (dry mouth) is a sensation arising in conditions that impair saliva secretion. Caused by a substantial reduction in saliva, dry mouth not only causes discomfort but also adversely affects swallowing and oral and dental health.

Where, how and why is saliva secreted?

Salivary gland structures responsible for saliva production are located anatomically in the cheek, beneath the jaw and under the tongue. These glands produce approximately 1500 ml of saliva daily. Saliva contains amylase, an enzyme involved in food digestion; immunoglobulin molecules and lysozyme belonging to the defense system; and, as in all bodily secretions, appropriate proportions of electrolytes, organic compounds and, of course, water. Throughout the day, stimulation of nerves involved in salivation produces 1-1,5 liters of saliva, and the fluid made in the glands flows continuously into the mouth through ducts.

To summarize saliva’s functions:

• Its digestive role is to moisten and soften food, assist swallowing and, through its amylase content, begin breaking down carbohydrates in food.
• Its lysozyme and immunoglobulins help destroy harmful microorganisms entering through the mouth.
• It maintains the sense of taste by keeping taste buds on the tongue moist.
• Saliva secreted at 1-1,5 liters daily has a washing effect important for protecting teeth and gums.

When saliva secretion decreases, these benefits are reversed, causing problems such as difficulty swallowing, an oral environment vulnerable to microbial agents, taste disturbances and difficulty speaking. Dry mouth may also range in intensity from mild dryness to severe burning and discomfort. This discomfort can sometimes be the patient’s most important complaint.

What causes impaired saliva secretion in cancer patients?

Many diseases and conditions cause dry mouth. The most likely causes encountered in cancer patients include:

• Medicines (chemotherapy drugs, pain medicines, antidepressants and diuretics).
• Radiotherapy (radiation treatment) to the head and neck.
• Factors such as insufficient body fluids or an oral fungal infection during cancer treatment.

Radiotherapy aside, causes of dry mouth are usually easier to manage, and eliminating the cause may be possible. However, radiation treatment, particularly for head and neck cancers, may be the only treatment option for the cancer, making the resulting dry mouth harder to resolve. Dry mouth severity may vary with the radiation dose delivered. At high doses, the problem may become chronic. Chemotherapy added to radiotherapy may make dry mouth more severe.

Treatment options for dry mouth in cancer patients

• Medicines: Pilokarbin acts by affecting the nerves that stimulate salivary glands to secrete. A medicine containing amifostine may be used to reduce the severity and frequency of radiation-induced dry mouth. These should not be used without a prescription or physician’s recommendation.
• Use of artificial saliva preparations and gels: Various products are available for this purpose and are recommended by physicians and dentists.
• To increase saliva secretion, gum chewing may be effective.
• Acupuncture treatment: Studies have shown its effectiveness in treating dry mouth, and it is performed at experienced acupuncture centers.

Beyond these treatment options, various precautions and dietary recommendations apply to dry mouth:

• If possible, patients receiving radiation treatment should have dental examinations before treatment, and efforts should be made to resolve dental and gum problems that could threaten oral health.
• Brush teeth regularly 3 times daily and clean with dental floss. Prepare salt or baking-soda rinses and rinse the mouth 4-6 times daily. Fluoride should be applied to the teeth. 
• Cool-mist humidification may be beneficial, particularly at night.
• Frequent sips of water are a method patients inevitably resort to. 
• Avoid alcohol, caffeine, acidic fruit juices and foods that are very sugary, sticky or spicy enough to burn the mouth.
• Choose soft, moist foods, preferably at room temperature or cold. 
• Do not use tobacco products.