External Radiation

External radiation is the most common type of radiation therapy used for head and neck cancer. It is used to aim high-energy rays or particles from outside the body into the tumor, thus passing through healthy tissue to varying degrees.

Types of External Radiation

There are multiple types of External Radiation, each is described below. More information about radiation can be found at www.radiologyinfo.org

Intensity Modulated Radiation Therapy (IMRT)

Intensity Modulated Radiation Therapy (IMRT) is commonly used for cancers of the head and neck. IMRT allows for the very careful delivery of external beam radiation therapy. This technology uses computer-controlled radiation beams in conjunction with three-dimensional computed tomography images of the tumor site and surrounding areas. It then moves around the patient as it delivers radiation. The tumor site receives the highest dose needed to destroy cancer cells while minimizing the dose and side-effects to surrounding healthy cells.

Image-guided radiotherapy (IGRT)

Image-guided radiotherapy (IGRT) – is particularly helpful for cancer sites in parts of the body that move (such as the lungs) or sites near major organs and tissues that should not receive radiation (such as the heart). Frequent imaging of the cancer site allows experts to provide a highly precise and accurate delivery of radiation. This allows the radiation oncologist to adjust the position of the patient or re-focus the radiation as needed.

Stereotactic body radiation therapy (SBRT)

Stereotactic body radiation therapy (SBRT) is used to precisely focus radiation beams toward tumors inside the body such as in the lung, spine and liver tumors. Patients may receive one to five treatments based on the tumor location. Since many physicians call this type of radiation therapy by the manufacture name, it can become confusing for a patient. Some machines or manufacture names are called CyberKnife, X-Knife, Novalis, Syngery -S or TrueBeam.

Stereotactic Radiosurgery (SRS)

Stereotactic Radiosurgery (SRS) is used most often for brain tumors by giving a large dose of radiation to a small tumor area. Once the exact location of the tumor is known, radiation is sent to the area from many different angles. The radiation is very precisely aimed to affect nearby tissues as little as possible. A form of photon beam, Gamma Knife is also widely used in or close to the brain using SRS. It’s called “radiosurgery” because it is so exact in where it delivers the radiation beams but there is no cutting or incision involved.

Three-dimensional conformal radiation therapy (3D-CRT)

Three-dimensional conformal radiation therapy (3D-CRT) uses imaging scans to create a three-dimensional model of the exact shape and size of the tumor. Then radiation beams are delivered from different directions designed to match the shape of the tumor. This helps to reduce radiation damage to normal tissues by focusing the radiation dose on the tumor’s exact shape and size.

How long does external radiation treatment take?

For patients with adenoid cystic carcinoma, a primary diagnosis in the head or neck area normally involves daily radiation treatments, 5 days a week (Monday through Friday) for 6 to 7 weeks. Weekend rest breaks allow time for normal cells to recover. 

The total dose of external radiation therapy is usually divided into smaller doses called fractions. This is because a large dose given one time can cause more damage to nearby normal tissues.  Furthermore, ACC cells normally divide slowly.  By spreading out the treatment plan, these cells are exposed to radiation as they divide overtime.   

Other radiation schedules are used for other areas of the body such as metastasis the lungs, liver, bones, brain.  For instance, radiation therapy might last only a few days (or less) when it’s used in these areas.  Factors such as the stage, grade, tumor location, side-effects and general health of the patient are taken into consideration when developing your treatment plan.