Oral candidiasis, also known as thrush, is a common occurrence for people going through cancer therapy. It is an opportunistic infection, developing due to decline in systemic or local immunity, including healthy oral microbiota---essentially an imbalance as protective bacteria are reduced in number allowing various fungal forms to proliferate. This may be due to reduction in saliva flow, poor oral hygiene, or mucositis.
It can be identified either by patient complaint or by signs. Symptoms may range from no symptoms to a burning sensation or pain and taste alteration, often described as a metallic taste. Signs include a distinct milky odor, redness, or a curdling white appearance. Angular cheilitis is also seen as red, cracked areas at the corner of the mouth. Microbial diagnosis is challenging as non-invasive yeast may also be detected.
Strategies to prevent candidiasis include good oral hygiene and removal and cleaning of any dentures or oral appliances at night. Use of probiotics has been proposed for prophylaxis in a recent review and shows promise. The authors report that Lactobacillus has been shown to inhibit adherence of candida to tissue and reduce growth in both in vitro and animal models. Other authors describe further research needed to identify an approach for human use, including dose, timing, and populations. Prophylactic use of a miconazole oral patch has been found effective, and low-dose fluconazole has been found to be preventive of
oral candidiasis in those undergoing radiation therapy in one study.
From Sroussi HY, Epstein JB, Bensadoun RJ et al. Common oral complications of head and neck cancer radiation therapy: mucositis, infections, saliva change, fibrosis, sensory dysfunctions, dental caries, periodontal disease, and osteoradionecrosis. Cancer Med. 2017 Dec;6(12):2918-2931. https://pubmed.ncbi.nlm.nih.gov/29071801/
Topical antifungal may be effective but, in some cases, systemic is required when it is more spread out. Systemic fluconazole is typically a drug of choice in these situations. However, the widespread use of fluconazole has been associated with the emergence of fluconazole resistant fungae.
Topical, localized therapy of clotrimazole troches are recommended as first-line therapies for milder oral fungal infections. If candidiasis develops during radiation therapy (RT), antifungal therapy should continue until completion of planned RT and patients should also be followed after completion of RT to determine if candidiasis recurs in order resume therapy or institute preventive protocols.
A Cochrane review of management of candidiasis in cancer patients receiving radiation and/or chemotherapy did not identify sufficient evidence to support the use of current interventions in treating oral candidiasis recommending that additional studies be conducted to address this gap of knowledge.
Topical azole or polyene antibiotics in the form of a lozenge, suspension or cream may be applied intra-orally. Instructions include applying nystatin four to six times daily, maintaining contact time on the mucosa as long as possible.
Some products, including oral rinse forms of nystatin that contain sugar, leads to increased caries risk particularly in dentate patients with hyposalivation. Topical fluconazole rinses can be compounded and have been examined and shown effective in cancer patients with candidiasis. Topical clotrimazole is available in a lozenge and cream but the assumption that its use as a topical agent completely avoids concerns of systemic
exposure and drug-drug interactions is not supported by reports of such complications. Topical miconazole is available in cream form, and in a muco-adhesive tablet (Loramyc® EU; Oravig® USA) that does not have sugar sweetening used once daily and has a broad spectrum of activity against Candida species.
Clinical presentation of the primary forms of oral candidosis. (a) acute pseudomembranous candidosis; (b) chronic erythematous candidosis; (c) acute erythematous candidosis; and (d) chronic hyperplastic candidosis. David Williams & Michael Lewis (2011) Pathogenesis and treatment of oral candidosis, Journal of Oral Microbiology, 3:1, DOI: 10.3402/jom.v3i0.5771.
As stated above, sucrose content of Nystatin suspension content can be high and would contribute to increased tooth decay in individuals at high risk, including those with dry mouth. If a topical lozenge or rinse is used, one should be selected without sugar in cases of individuals with natural teeth.
Labeling from Nystatin Oral Suspension. Note that second ingredient is sugar. From https://fda.report/DailyMed/b95ce95e-ea57-99d5-e053-2a95a90ab217
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