Radiation Therapy
PROCESS
Radiation therapy is a highly developed system of treatment using a stream of particles to treat cancer. The staff at 21st Century Oncology uses a precise series of steps to treat patients using radiation therapy.
Steps of radiation therapy:
Consultation
The first step is a visit to the radiation oncologist. During this visit, the radiation oncologist reviews all of the patient’s records, pathology reports and x-ray films and performs a physical examination. At the end of the exam, he or she discusses the recommendations for radiation treatment with the patient and family. Several appointments are made for the patient so that a plan for the radiation treatment can be developed. These appointments include one or two planning sessions (called simulations) and a date to start treatment.
Simulation
The second step is an appointment for simulation. During this appointment, the patient is placed in position on a flat x-ray table that gives the best access to the area needing treatment. This is called the treatment position. To make sure that the radiation treats exactly the same place in the body each time, an immobilization device such as a mold or mask may be designed to help the patient assume in the same position each day. For example, a mask may be required for treatment of the head and neck region. A mold may be used to treat an area of the leg or arm. However, immobilization devices are not necessary for all patients. While the patient lies in the treatment position, x-rays or a CT scan is performed of the area to be treated. The radiation oncologist uses these x-rays to design the exact size and area to be treated by the radiation. In some cases it may be necessary to use contrast material. For example, if a patient’s pelvis is to be treated, contrast material is inserted into the rectum and bladder so that these organs are visible on the x-ray film. In other cases, small pieces of wire are placed on the skin to enable the radiation oncologist to find certain landmarks that would not otherwise show up on the x-rays. Once all the x-rays are obtained, any contrast material and/or pieces of wire are removed. Several small marks are left on the skin to help identify the area to be treated. These marks are used to confirm the treatment plan during the next visit and on each treatment day.
Treatment planning
The next step involves only the radiation oncologist, physics staff, and dosimetrists. The radiation oncologist, using the x-rays obtained during the simulation, designs the treatment field. The physics staff designs special shielding blocks or plans that shape the radiation beam to the treatment field and help shield normal tissue from the radiation beam. In addition, special computer plans are developed by the dosimetrist that help the radiation oncologist develop a treatment plan that gives the best radiation dose distribution to the treatment field selected. Depending on the treatment plan, some patients return for a second simulation appointment. During this appointment the shielding blocks are placed at the top of the machine, and an x-ray is taken. The radiation oncologist compares this x-ray with the simulation film (or planning films) to ensure accuracy. During this visit, additional lines are drawn on the skin to outline the exact treatment field for the radiation therapists use. The lines remain on the skin throughout the course of treatment.
Start of treatment
Treatment can now start. The radiation therapists are responsible for positioning the patient and delivering the radiation dose. On the first day of treatment, the patient is placed in the treatment position. The therapists use several techniques to accurately reproduce the treatment, including laser lights, field lights, and SSD measurements. The laser lights are used to make sure the patient is level and straight on the table. The field light corresponds to the skin marks, and the SSD is the number that represents the distance from the source of radiation to the skin. Once everything is in place, the therapists leave the room. No one is allowed to stay in the room with the patient during the actual irradiation. The patient is observed on TV monitors outside the room and also can speak to the therapists if necessary. The treatment itself is very short. The patient is usually in the room less than 30 minutes per treatment, and most of this time is spent getting the treatment fields accurately positioned.
Several x-ray films are taken on the first day of treatment and weekly thereafter, or if changes of the treatment field are necessary. These films are not used to determine if the cancer has decreased in size, but rather are compared with the initial planning films to make sure that the fields have not shifted. On approval of the treatment x-rays, and with the patient’s permission, permanent small tattoos (approximately the size of a pinhead) are placed on the skin in 5 or 6 spots to mark the corners and center of the treatment field. These tattoos are necessary for two reasons: (1) if the skin markings come off during the course of treatment, the field can be reproduced by locating the tattoos; and (2) if in the future further treatments are required, the previous fields can be located and over-treatment can be avoided. Radiation treatments do not hurt, but do require cooperation of the patient in remaining completely still. When the patient is a child, safety straps must be used. They are not tight; they are just a preventive measure. Parents must remain outside the room but can talk to their child on the intercom. It is recommended that the child bring a favorite tape to listen to while undergoing treatment.