Radiation Therapy

What Is Radiation Therapy?

Radiation therapy uses high-energy X-rays, electron beams, or radiaoactive isotopes to attack cancer. Radiation therapy causes cancer cell death by damaging the chromosomes in the cell so that the cells cannot multiply.

Radiation therapy is a local treatment -- aimed directly at the cancer. Aside from its use as a single treatment, radiation therapy has been shown to enhance the effects of chemotherapy. It can be used in combination with chemotherapy to shrink a tumor before it's removed. For tumors that can't be removed, radiation can reduce or alleviate the pain, bleeding, or blockages caused by these tumors.

Radiation and Colorectal Cancer: Who's a Candidate?

The role of radiation in colon cancer isn't well defined. There are a few in whom the addition of local or regional radiation may improve control of the disease and lengthen survival.

Radiation therapy plays a much more important role in treating rectal cancer where it can be used to reduce the size of a tumor before local excision of the cancer.

Radiation therapy is also used as adjuvant therapy (additional therapy) with chemotherapy for rectal cancer to improve survival rates.

In some cases, such as if the tumor is small or you are very old or sick, radion alone can be used to treat the tumor.

When rectal cancer reoccurs, it is very debilitating and often associated with chronic pelvic pain. Therefore, pelvic radiation can be administered before rectal cancer surgery, after surgery or both before and after surgery to help relieve the pain and other symptoms associated with the disease.

What Types of Radiation Therapy are Available?

Successful radiation therapy depends on delivering the proper amount of radiation to the cancer in the best, and most effective way. There are several types of radiation therapy.

External Beam Radiation Therapy

External beam radiation therapy is the most common form of radiation therapy. Before treatment begins, detailed planning or simulation is performed. During simulation, a team of specialists, including a radiation oncologist, will use measurements from scans and calculations to determine the precise location to aim the radiation. They will tattoo small dots on your body to indicate where to target the beam to ensure they radiate the same location at every treatment. This process may take several hours.

During the treatment, you will be positioned on a table so that a beam from a machine outside the body may be aimed at the tumor. The radiation treatment itself lasts only a few minutes, but it may be given 5 times a week for several weeks, and sometimes a couple of times per day for several weeks.

Internal Radiation Therapy

Internal systemic radiation therapy involves injecting radioactive isotopes either into a vein or into an organ. One of the most common types of systemic radiation therapy is radioactive iodine (I-131), which is given for some types of thyroid cancer. Another type of systemic radiation therapy is the use of Strontium-89 (Metastron). This isotope is used to treat cancer that has spread to the bone.