Managing dry mouth after radiotherapy for NPC.

Dry mouth is very common after radiotherapy to the head and neck area. This is due to radiation effect to the parotid, submandibular and sublingual salivary glands. These caused the reduction of saliva production resulting in dry mouth.

The first thing a patient will notice during the radiotherapy course is the thickening of saliva about 4-5 weeks after starting the radiotherapy. After completion of radiotherapy, the saliva production is reduced and becomes very thick. Due to the effect on the inner lining of the mouth and back of throat, this can further cause ulcers, inflammation and pain leading to painful swallowing.

It is common for a patient to carry small bottles of water to rinse and to drink during the process.

Patient always ask doctor 3 questions about the dry mouth:

1) Will it get better?
2) If it will get better, then when will it happen?
3) Is there any medication or food that will help the dry mouth beside drinking water?

In the older days, radiotherapy is given as a parallel opposed beams. This means the radiotherapy enters on the left side and exits on the right side and all the areas of the mouth, jaw and neck areas are treated. In modern days, there is now a better way to deliver the radiotherapy and this technique is called IMRT - Intensity Modulated Radiotherapy. What this means is really given the radiotherapy in multiple beams, like a circular beams that spread out the high doses so that to spare certain organ at risk and in this case the salivary glands. As a results of this, comparing the older radiotherapy that cause 100% salivary loss with 0% chance of recovery, it is now possible to say that with IMRT, salivary production recovery is possible to a certain degree and completely dry mouth with no salivary production at all is rare.

With IMRT, saliva recovery happens around 6 months on completion of radiotherapy and will continue to improve up to 2 years after the completion of radiotherapy. It is unusual for further recovery beyond 2 years.

To deal with the dry mouth, drinking sips of water is still the best way to wet the mouth and throat. However, water has no addictives in it. In saliva, there are multiple enzymes that protect the inner lining of the mouth and the teeth and if this is lost, there are higher chances of getting gum and teeth diseases.

There are now artificial saliva equivalent which contains salivary enzymes to help gum and teeth decay and at the same time provides relief from dry mouth. BIOTENE products from GSK are a range of products from mouthwash, gel and toothpaste that contain such enzymes and patient frequently reported good symptomatic relief and happy with these products. ORAL SEVEN are another similar range of products and both BRANDS are available for sale at pharmacists in Singapore without a doctor's prescription.

To stimulate saliva production, the act of chewing helps. Patient can chew sugar free gums or if no gums are available (since gums are prohibited from sale in Singapore), then the act of chewing, tongue and jaw exercises usually helps as well.

Lack of taste is a common complaint as well since the food cannot be mixed with saliva for the tongue to taste the food. The taste buds from the tongue are also partially destroyed by the radiotherapy. The tip of the tongue that taste sweetness usually recovers first compared with the rest.

The GC Tooth Mousse brand is a HIGH flouride mousse. It is better than normal toothpaste due to the stronger fluoride content and will fortify the teeth against tooth decay. This is available via selected dental practices throughout Singapore but not available in normal retail market.

In summary,

With IMRT (this is now the gold standard of radiotherapy in Singapore in NPC treatment), saliva production tends to recover although not completely. It takes 6 months to 2 years for the saliva production to recover slowly. In the meantime, try to chew sugar free gum, do chewing and tongue exercises to stimulate saliva production. There are multiple over the counter supportive care products that contains artificial saliva that helps and there is a need to see your dentist every 6 months for dental check. A high flouride compound is highly recommended to strengthen against tooth decay.