The likelihood is high that aggressive cancer treatment will have toxic effects on normal cells as well as cancer cells. The gastrointestinal tract, including the mouth, is particularly prone to damage. This is true whether the treatment is radiation or chemotherapy. Most patients being treated for head and neck cancer will experience some oral complications, and while most of these are manageable, complications can sometimes become severe enough that treatment must be completely stopped. In addition, surgical solutions to tumor removal may lead to oral and nutritional problems as well.
The most common oral problems occurring after radiation and chemotherapy are mucositis (an inflammation of the mucous membranes in the mouth), infection, pain, and bleeding. Other possible complications might include dehydration and malnutrition, commonly brought on by difficulties in swallowing (dysphagia). Radiation therapy to the head and neck may injure the glands that produce saliva (xerostomia), or damage the muscles and joints of the jaw and neck (trismus). These treatments may also cause hypovascularization (reduction in blood vessels and blood supply) of the bones of the maxilla or mandible (the bones of the mouth). In addition, treatments may affect other forms of dental disease (caries, or soft tissue complications), or even cause bone death (osteonecrosis).
By identifying patients at risk for oral complications, health care providers are able to start preventive measures before cancer therapy begins, reducing the occurrence of problems brought about by different treatment modalities. The most important risk factors leading to problems are oral or dental disease that already exists, and poor oral care during cancer therapy. Other risk factors include the type of cancer, the chemotherapy type and schedule used, the area irradiated and how much radiation is given, how low blood counts are decreased and for how long, the patient's age, and the general condition of the patient's health pre-treatment.
Pre-existing oral conditions may increase the risk of infection or other problems. Problems such as calculus and tartar on the teeth, broken teeth, the condition and quality of existing dental repairs such as crowns or fillings, periodontal disease, and appliances such as bridges, partial dentures, or other removable fixtures can make therapy more difficult later on. Bacteria and fungi can live in the mouth, and may develop into an infection when the immune system is not working well, or when white blood cell counts are low. Both of these factors can be caused by the treatment methods used. Where the gums (gingiva) or other soft tissues are irritated, tissues can thin and waste away, causing sores in the mouth. These complications can result in a significant reduction in the quality of life for the patient.