What causes Oral Mucositis?

Oral mucositis is commonly found in cancer patients receiving chemotherapy and/or radiation for head and neck cancers

Chemotherapy and radiation work by killing rapidly dividing cancer cells that are already there. Unfortunately, these treatments can't tell the difference between dividing healthy cells and dividing cancer cells. The side effects of therapy, including oral mucositis (OM), happen when healthy dividing cells are also killed. The combination of chemotherapy and radiation increases the risk of developing severe oral mucositis. The symptoms of oral mucositis also tend to get worse the longer the radiation treatment lasts.

During radiation for head and neck cancer or Hematopoietic Stem Cell Transplant (HSCT) (sometimes called a Bone Marrow Transplant [BMT]), the beam of radiation passes near and through the mouth. Normally healthy cells in the mouth quickly divide and replace surface cells with new cells. However, radiation kills these dividing cells meaning the surface cells cannot be replaced, causing ulcers to form.

Chemotherapy and radiation to the head and neck damage the glands through the mouth that produce saliva (spit), causing the mouth to be drier than normal. A dry mouth means the natural lubrication saliva provides for eating is much less. This makes it difficult to swallow and the mouth is more likely to be damaged by hard food that is normally washed away by saliva.

The type, dosing and duration of chemotherapy used to treat the cancer will affect the likelihood of developing oral mucositis. There are many types of chemotherapy that are known to cause oral mucositis. Some of these therapies are listed below:¹⁷

• 5-fluorouracil
• methotrexate
• doxorubicin
• etoposide
• melphalan
• cytosine arabinoside
• cyclophosphamide

All radiation that passes in and near the mouth is very likely to cause oral mucositis.

The estimated frequency of oral mucositis with varying treatments is shown here:^2,3

Mucositis generally lasts for 16 days after the start of cancer treatment, with healing starting on about the 12^th day after the cancer treatment has stopped.¹¹

It varies depending on the type of cancer treatment:

Chemotherapy

• In patients treated with chemotherapy, oral mucositis can develop from the first day of treatment. Initially, only the deep-lying tissue is affected and there are no visible signs inside the mouth.¹¹
• Generally, the symptoms only appear 5 to 8 days after starting treatment. Oral mucositis can persist for 7 to 14 days before healing of the ulcers  starts.¹¹
• In some patients, oral mucositis can last longer.¹¹

Radiation

• The symptoms of oral mucositis appear later (generally after 2 weeks). Healing cannot start until after the treatment has ended. The symptoms of oral mucositis can then persist for up to 8 weeks.¹¹

Numerous factors contribute to the risk of oral mucositis including:

• The type of anticancer treatment received⁶
• Having received anticancer treatment previously²⁵
• Having radiation therapy for head and neck cancer²⁵
• Age (children and the elderly develop oral mucositis more often)²⁵
• Ethnicity (Caucasians are at a higher risk than African-Americans)²⁵
• Receiving a higher intensity anticancer treatment²⁵
• Having previously suffered with a history of oral mucositis⁶
• Poor oral health and oral hygiene¹⁴
• Smoking¹⁴
• Drinking alcohol¹⁴

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