Definition
Salivary gland dysfunction includes either the presence of xerostomia (a subjective sensation of a dry mouth) or salivary gland hypofunction (hyposalivation or measurable reduction in production of saliva).r Xerostomia may be experienced without a decrease in saliva production and may result from a change in the composition of the saliva produced.r
Salivary gland dysfunction is associated with a range of oral problems including oral discomfort, altered taste and speech, difficulty chewing and swallowing, dental decay, oral candidiasis, mucositis and other oral infections.r It can result in significant impairment of a patient’s quality of life.r
Pathophysiology
The salivary glands include major glands (parotid, submandibular and sublingual glands) and minor glands (scattered throughout the oral mucosa including the lips, soft palate and the ventrum of the tongue). Salivary gland dysfunction can result from:
- radiation therapy where the minor and major salivary glands and associated nerves and endothelium can be damaged by radiation, e.g. treatment to the head and neck region or total body irradiationr
- medications that alter the flow and consistency of saliva
- salivary gland graft-versus-host disease (GvHD) in patients undergoing haematopoietic stem cell transplant. Xerostomia can result from the chronic fibrotic changes of the mucosa and adjacent salivary ducts.r
Incidence/prevalence
Xerostomia secondary to radiation therapy-induced salivary damage can affect a significant proportion of patients with head and neck malignancy treated with radiation therapy.r
Approximately 80% of patients with GvHD demonstrate oral involvement which can include xerostomia and salivary gland dysfunction.r Exact prevalence and incidence is difficult to determine as there is no universally accepted case definition of oral GvHD.
Onset/duration
During radiation treatment, salivary gland dysfunction commences within the first week of treatment, continues to decline for the remainder of treatment and for 6-8 months after treatment is complete.r Complete recovery can take 1-5 years, however, salivary gland dysfunction can be permanent.r In patients with GvHD, the onset of salivary dysfunction usually occurs rapidly following transplantation.r
Risk factors
There are multiple risk factors that predispose patients to the development of xerostomia, including:
- radiation therapy to the salivary glands
- concomitant chemotherapy
- allogeneic stem cell transplant
- medications (e.g. chemotherapy, antiemetics, antihistamines, antidiarrhoeals, antianxiety drugs and opioid analgesics).