Chemotherapy is a cancer treatment designed to eliminate rapidly dividing cancer cells throughout the body. A common side effect is the increased risk of developing oral candidiasis, or thrush, a fungal infection caused by an overgrowth of Candida yeast. This fungus is naturally present in the mouth but is usually kept under control by the body’s immune defenses. Chemotherapy significantly raises the likelihood of this infection by disrupting the oral environment and weakening the immune system’s ability to manage the fungus.
Understanding the Link Between Chemotherapy and Immune Suppression
Chemotherapy drugs target rapidly dividing cells, including healthy cells found in the bone marrow and the lining of the mouth. Damage to the bone marrow leads to myelosuppression, which reduces the production of blood cells, including white blood cells.
A reduction in neutrophils, a specific type of white blood cell, causes neutropenia, severely compromising the body’s defense mechanisms. Since neutrophils fight off fungi like Candida, their low count leaves the body vulnerable to opportunistic infections like thrush. This immune suppression typically occurs days or weeks after a chemotherapy session, coinciding with the peak risk for infections.
Simultaneously, chemotherapy agents directly damage the mucosal lining of the mouth, throat, and gastrointestinal tract, leading to inflammation and ulceration known as mucositis or stomatitis. This damage breaks down the protective physical barrier that normally prevents microorganisms from penetrating the tissue. The damaged tissue allows Candida to multiply and establish an infection.
The combination of a compromised physical barrier and depleted immune defense creates a high-risk scenario for thrush. Furthermore, broad-spectrum antibiotics, often required during periods of neutropenia to combat bacterial infections, can further disrupt the normal microbial flora in the mouth. This imbalance allows the Candida fungus to proliferate without competition, contributing to the development of candidiasis.
Recognizing the Signs of Oral and Esophageal Thrush
The most identifiable sign of oral thrush is the appearance of creamy white patches or lesions inside the mouth. These patches often resemble cottage cheese and may be found on the tongue, cheeks, gums, or the roof of the mouth. Unlike milk residue, these patches cannot be easily wiped away; scraping them off typically reveals a painful, red, and sometimes bleeding area underneath.
Other common symptoms include a burning or sore sensation in the mouth, which makes eating and swallowing difficult. Individuals may also report a cottony or dry feeling, or a noticeable change in taste. Redness and painful cracking at the corners of the mouth, known as angular cheilitis, may also develop.
If the fungal infection progresses, it can spread downward into the esophagus, leading to a more serious condition called esophageal candidiasis. Symptoms of esophageal involvement include pain when swallowing (odynophagia) or difficulty swallowing (dysphagia), often described as feeling like food is stuck in the throat or chest. The presence of oral thrush is a strong indicator that esophageal thrush may also be present.
Effective Strategies for Management and Prevention
The management of thrush revolves around the use of antifungal medications, which must be prescribed and closely monitored by the oncology care team. For localized infections, topical treatments such as antifungal lozenges or liquid suspensions that are swished and then swallowed may be used. However, clinical evidence suggests that systemic antifungal drugs are often more effective at preventing candidiasis than purely topical agents for those undergoing cancer treatment.
For more severe or persistent cases, or when the infection has spread to the esophagus, systemic antifungal medications taken orally or administered intravenously become necessary. It is important to complete the entire course of medication as prescribed, even if the symptoms begin to improve quickly, to ensure the full elimination of the fungal overgrowth.
Preventive home care is essential for minimizing the risk of thrush during chemotherapy. Maintaining rigorous oral hygiene is paramount, which includes using a soft-bristled toothbrush to gently clean the teeth and gums. Patients should avoid commercial mouthwashes that contain alcohol, as these can irritate the already sensitive oral mucosa and contribute to dryness.
Instead, rinsing the mouth several times a day with a mild saline solution or a prescribed mixture can help keep the mouth clean and moist. Dry mouth, or xerostomia, is a common side effect that increases the risk of infection, so managing it with saliva substitutes or by frequently sipping water is helpful. Dietary adjustments can also support prevention, such as limiting the intake of foods and drinks high in sugar and yeast, which can fuel the growth of Candida.