Radiation therapy for oral cancer

Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is sometimes used to treat oral cancer. Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You may also receive other treatments.

Advantages of radiation therapy for oral cancer are that the normal look and functions of the mouth are maintained and general anesthesia is not needed. If radiation therapy is not successful in treating the oral cancer, salvage surgery (surgery to remove any cancer that remains after treatment) is still possible.

Disadvantages of radiation therapy for oral cancer are the side effects. Radiation therapy is not as effective as surgery for large tumours and surgery after radiation therapy is often more difficult and more dangerous.

Radiation therapy is often used after surgery for oral cancer. It may be used as the main treatment for oral cancer in certain situations where surgery is not an option.

Radiation therapy is used after surgery for oral cancers with a high risk of coming back (recurring). These include cancers with any of the following features:

  • larger tumours
  • close or positive surgical margins
  • tumours that have grown along or into nerves (called perineural invasion)
  • spread to the blood vessels and lymph nodes (lymphovascular invasion)
  • two or more positive lymph nodes
  • cancer in lymph nodes that has spread outside the capsule (extracapsular extension)
  • cancer in a lymph node that is greater than 3 cm

Radiation therapy is sometimes combined with chemotherapy to treat oral cancer. This is called chemoradiation. The 2 treatments are given during the same time period.

Radiation therapy is given for different reasons. You may have radiation therapy or chemoradiation to:

  • destroy the cancer cells in the body
  • shrink a tumour before other treatments such as surgery or chemotherapy (called neoadjuvant therapy)
  • destroy cancer cells that may be left behind after surgery or chemotherapy to reduce the risk that the cancer will come back (called adjuvant therapy)
  • relieve pain or control the symptoms of advanced oral cancer (called palliative therapy)

Before radiation therapy, it is important for you to have a dental exam and have any needed dental work done. It is also important to stop smoking as smoking can make radiation therapy less effective and make side effects worse.

The following types of radiation therapy are most commonly used to treat oral cancer.

External beam radiation therapy

During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. The size of the area treated and the dose of radiation depend on the size of the tumour, if the tumour has grown into surrounding tissue and if the cancer has spread.

Doctors may use the following types of external beam radiation therapy to target the area to be treated and save as much surrounding normal tissue as possible.

3D conformal radiation therapy (3D-CRT) delivers radiation to the tumour from different directions. The radiation oncologist uses MRI images to map the exact location and shape of the tumour. Several radiation beams are then shaped and aimed at the tumour to treat it from all angles. Each beam alone is fairly weak and not likely to damage normal tissues, but a higher dose of radiation is delivered to the tumour at once.

Intensity-modulated radiation therapy (IMRT) delivers radiation from many different angles to treat the entire tumour, but IMRT also allows the radiation oncologist to adjust the strength of the individual beams. This allows a higher dose to be delivered to the tumour and reduces the dose of radiation reaching nearby normal tissues.


Brachytherapy is internal radiation therapy. It uses a radioactive material called a radioactive isotope. It is placed right into the tumour or very close to it. Radioactive materials can also be placed in the area where the tumour was removed. The radiation kills the cancer cells over time. Brachytherapy may sometimes be used for small tumours in the mouth, including those on the tongue, lip, floor of the mouth and inner lining of the cheek (buccal mucosa).

There are 2 different ways that brachytherapy can be given.

Interstitial brachytherapy for oral cancer uses hollow, thin needles. A radioactive substance is placed into the needles and delivered directly to the tumour.

Intraoral cone for oral cancer uses a cone placed inside the mouth to deliver the radiation.

Brachytherapy may be used in combination with external beam radiation therapy.

Side effects

Side effects can happen with any type of treatment for oral cancer, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.

Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation and the treatment schedule. Some common side effects of radiation therapy used for oral cancer are:

Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

Questions to ask about radiation therapy

Find out more about radiation therapy and side effects of radiation to the head and neck. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.

Expert review and references

  • American Cancer Society. Oral Cavity and Oropharyngeal Cancer. 2016.
  • American Society of Clinical Oncology. Oral and Oropharyngeal cancer. 2016: http://www.cancer.net/.
  • Cancer Care Ontario. Evidence-Based Series 5-3: The Management of Head and Neck Cancer in Ontario. 2009.
  • Cancer Research UK. The Mouth and Oropharynx. Cancer Research UK; 2016.
  • Koch WM, Stafford E, Chung C, Quon H . Cancer of the oral cavity. Harrison LB, Sessions RB, Kies MS. Head and Neck Cancer: A Multidisciplinary Approach. 4th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2014: 16A:335-356.
  • Mendenhall WM, Werning JW and Pfister DG . Treatment of head and neck cancer. DeVita VT Jr, Lawrence TS, & Rosenberg SA. Cancer: Principles & Practice of Oncology. 9th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011: 72:729-80.
  • National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Head and Neck Cancers (Version 1.2015). 2015.
  • Scully C. Medscape Reference: Cancers of the Oral Mucosa. 2016.