Radiation Therapy for Colorectal Cancer
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 five times a week for several weeks, and sometimes a couple of times per day for several weeks.
There are many types of external beam radiation. These include, 2D, 3D conformal, IMRT, IGRT, and proton beam therapy.
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. This type of radiation is taken orally. Another type of systemic radiation therapy is the use of certain radioactive isotopes that have a special affinity for bone. These isotopes are used to treat breast and prostate cancers that have spread to the bone, and cause severe pain.
Interstitial radiation therapy (also known as brachytherapy) is the process of placing radioactive sources directly into the tumor. These radioactive sources can be temporary (removed after the proper dose is reached) or permanent. The major use of this type of radiation is for prostate cancer.
Intracavitary radiation therapy is used most commonly in gynecological cancers, such as cancer of the uterus. In this procedure, radioactive sources are placed into applicators that are positioned into the area affected. They are left in place for several hours and then removed. The patient must stay in bed in the hospital while the radiation is in place. In selected patients with early rectal cancer, intracavitary radiation is a successful treatment.
What Are the Side Effects of Radiation Therapy?
The side effects of radiation therapy are, for the most part, specific to the area of the body being radiated. Some general side effects may include skin irritation and fatigue. Other side effects might include nausea and vomiting (for radiation given in the area of the stomach), hair loss (for radiation given to the head), sore throat, and difficulty swallowing (for radiation given to the neck or chest), and diarrhea (for radiation given to the lower back or abdomen). There are medications and techniques that can help control side effects. Be sure to discuss any side effects with your doctor so that they can be managed properly.