External Radiation Therapy

External (or external beam) radiation therapy is the most widely used method of delivering radiation. The radiation is focused from a source outside the body onto the area affected by the cancer. It’s a lot like getting an x-ray, but for a longer time. Radiation passes through but is not stored in the body. Patients do not become radioactive.

External radiation is given by variety of machines, most commonly a linear accelerator (or linac). Careful treatment planning allows the x-rays to destroy cancer cells while limiting any effect on surrounding normal tissue. The process of external beam therapy can be divided into four parts: Simulation, Treatment Planning, Plan Verification, and Treatment Delivery.

What's involved in planning my treatment?

After a physical exam and a review of your medical history and test results, you will be scheduled for a Simulation session. The radiation therapist will ask you to lie still on a CT scan table while cross-sectional images of your anatomy are obtained. These are used to define the exact place in your body where the radiation will be aimed. The doctor checks the size of the tumor, identifies the normal tissues in the area and also the areas where the tumor is more likely to spread.

“Immobilization devices” may be custom-made for you during Simulation to help you remain still during treatment and to insure that the radiation beam is aimed correctly. The therapist also marks the field with freckle-sized dots of semi-permanent ink or with tiny permanent dots like a tattoo.

The dosimetrist, radiation physicist and radiation oncologist then use a Treatment Planning computer system to calculate the radiation dose, delivery time and treatment technique. Your doctor analyzes all the relevant information and decides how much radiation is needed, how it will be given, and how many treatments you need.

The Plan Verification part of the process is really a second “mini-simulation” that may happen on or before your first Treatment Delivery day. It’s like a dress rehearsal for a play where the therapy team finalizes all of the preparations for treatment.

How long does the treatment take and what happens during each visit?

External radiation therapy usually is given once a day, 4-5 days a week for 3 to 8 weeks. The total dose of radiation and the number of treatments you need will depend on the size, type and location of your cancer, your general health, and any other treatments you are receiving.

Radiation therapy treatments are totally painless and take only a few minutes. However each session can last 15 to 30 minutes because of the time it takes to set up the equipment and place you in the correct position. You will lie on a treatment table positioned under the radiation machine. You should remain still but do not have to hold your breath - just relax and breathe normally.

Once you are in position, the radiation therapist will leave the room to turn on the machine. Visual and voice contact is always maintained by closed circuit television and by intercom. The therapist controls the machine as it moves around you to aim at the treatment area from different angles. You will hear the machine making humming noises, but will feel nothing unusual. If you are concerned about anything that happens in the treatment room, alert your therapist. The machine can be stopped at any time.

What are: 3D Conformal Radiation Therapy? IMRT? TomoTherapy?

All of these terms refer to specific advanced treatment planning and delivery technologies that enable Advanced ROS doctors to protect normal tissues so that the highest possible dose of radiation can be safely delivered to the tumor. These tools give us the most accurate and specific information to plan your treatment and precise control over the radiation delivered.

A 3D Conformal treatment planning computer uses CT images to map the 3-dimensional location of the cancer in the body. The physician can then visualize the tumor, bony anatomy and organs from the radiation “beam’s eye view” and try different arrangements on the patient, a process known as virtual simulation. Radiation beams can then be directed to conform to the exact shape of the cancer.

Intensity Modulated Radiation Therapy (IMRT) is a 3D CRT-based delivery technique which allows doctors to further lessen injury to normal body tissues by varying the shape and intensity of the radiation beam.

TomoTherapy® is the newest concept in radiation therapy that combines the capabilities of a CT scanner and a linear accelerator into a single unit. It delivers a very sophisticated form of IMRT and integrates treatment planning, delivery and verification into one system. Advanced ROS is the first facility in the Northeastern U.S. and one of only thirty locations worldwide to offer TomoTherapy.