External Radiation Therapy

External beam radiation therapy involves a series of daily outpatient treatments to accurately deliver radiation to the cancer. Treatments are painless. They are usually given in a series of daily sessions, Monday through Friday, for up to five to six weeks.

Before beginning treatment, you will be scheduled for a planning session to map out the treatment area. This procedure is called a simulation. Simulation involves having a CT scan and possibly an MRI, which can help visualize soft tissues near the cancer. You may also receive small pen marks or tattoos on your skin at the simulation that will help the radiation therapists precisely position you each time for daily treatment. Typically, radiation therapy is done with high energy X-rays, also called photons. Another form of external radiation is proton beam therapy (PBT), which, in certain rare circumstances, may reduce radiation dose to normal parts of the body not involved by the cancer.

Different techniques can be used for treatment. Three-dimensional conformal radiotherapy (3-D CRT) combines multiple radiation treatment fields to deliver precise doses of radiation to the affected area. Tailoring each of the radiation beams to focus on the tumor delivers a high dose of radiation to the tumor and lowers the dose to nearby healthy tissue. Intensity modulated radiation therapy (IMRT) is another advance in the delivery of radiation therapy.

Modifying the intensity of the radiation within each of the beams allows more precise adjustment of doses delivered to the tissues within the target area. Your radiation oncologist will evaluate you for the best form of treatment.