WHAT IS RADIATION THERAPY?
Radiation therapy (also called radiotherapy) uses high-energy x-rays to kill cancer cells. The treatment works by damaging the genetic material, or DNA, within the cells, making it more difficult for them to divide.
During radiation therapy both normal and cancer cells are affected, but normal cells can recover quickly, while the abnormal, rapidly dividing cancer cells, are permanently damaged. The goal is to kill any cancer cells that might remain in the local area after surgery, and to prevent cancer from coming back, or recurring.
Radiation is directed from several angles to minimize tissue damage
For cancer located in the colon, the most effective treatment is surgery. Radiation therapy is used primarily for rectal cancer, where it is usually given before surgery, to shrink the tumor and improve the results of the resection. Radiation therapy given before surgery is a neoadjuvant therapy.
Unlike chemotherapy—which is a systemic treatment that treats the entire body—radiation therapy is considered a local treatment, because it treats only the cancer area.
Your health care team may recommend radiation therapy if you have stage III cancer.
If you have stage IV cancer, or recurrent colon cancer and you are too ill to have surgery, you may receive radiation
therapy alone or in combination with chemotherapy. These treatments will not cure advanced-stage colon cancer, but they can relieve some cancer symptoms and temporarily shrink tumors that are blocking the colon.
Radiation Therapy Treatment
Radiation therapy is administered at medical centers staffed by teams of professionals specializing in radiation oncology.
There are several ways to administer radiation therapy. The oldest and most common, external beam radiation therapy, or EBRT, uses a complex device that aims a beam of radiation at the cancer area.
Another method, brachytherapy, uses tiny amounts of radioactive material temporarily placed into or near the tumor.
A type of external beam radiation therapy is called endocavitary therapy. Instead of the beam passing through the body, a radiation-emitting device is inserted into the anus, and the rectal tumor is treated directly.
A newer radiation technique for treating colorectal cancer is called intraoperative radiation therapy, or IORT. This form of therapy is used for patients with extensive local spread of rectal cancer. IORT is administered after the surgeon has removed the tumor, but while the patient is still in the operating room. Since radiation is delivered directly to a specific area in the pelvis, higher-than-normal doses can be given.