Treatment Goal
Radiotherapy is sometimes useful to treat localized lymphomas, especially Hodgkin’s lymphoma, and central nervous system lymphoblastic leukemia. In these situations radiation may serve as primary therapy in a treatment program to cure the disease. Radiation therapy may also be useful to control symptoms when local cancer growths cause pain as a result of pressure on bone or nerve, or when the function of vital organs such as the bowel, or respiratory system are involved.
The goal of radiation therapy in the case of blood-related cancers is to destroy the cancer tissue under treatment. In order to do this a specific dose is given to the target tissue while a small dose is given to normal tissue. Radiotherapy is used less frequently than chemotherapy for blood-related cancers because these diseases are usually widespread at the time of diagnosis. Total body irradiation is a treatment in which the radiation dose is the same over the total body surface. It may be used to eliminate or reduce the number of cancer cells (as in leukemia or lymphoma) prior to a stem cell transplant. The total body radiation suppresses the patient’s immune system to prevent rejection of a donor’s stem cells. Radiation of the entire body has been used to treat some lymphocytic tumors but the results have not been conclusive.
Administration of the Treatment
The radiation therapy is given to the patient in the form of gamma rays or x-rays. The radiation oncologist establishes the treatment dose. Equipment used to generate this form of therapy falls under two main types. The most common is a linear accelerator, a machine that delivers high volt x-rays, the other is a Cobalt 60 machine. Linear accelerators make it possible to decrease or avoid skin reactions from radiotherapy. They also make the treatments more focused so that there is less “scatter” of radiation to nearby normal tissues. Electron beam therapy can also be used. This radiation penetrates only into the skin and is very useful in the treatment of cutaneous (skin) lymphomas.
The dose used depends on the disease and the reason for the treatment. The total dose is delivered to the patient during a series of visits, usually spread over several weeks. This approach is called “fractionation of the dose” and is used because it minimizes side effects. The planned fractional dose is delivered each day to the area specified by the radiation oncologist.
A radiation oncologist is a physician who is trained to administer radiation treatments and evaluate patients who may need radiation treatment. The radiation oncologist also determines if a specific tumor will respond to radiation treatments and the number of treatments that will be required.
Preparation for Treatment
Prior to the start of treatment, patients are prepared for the treatment by “simulation”. The purpose of the simulation procedure is to set up the best location for the treatment and establish a position that will be used in each treatment. The simulation takes place in equipment that is very similar to the actual treatment equipment. The patient is positioned in a manner that will be repeated during each treatment session. In this way the time consuming process of positioning the patient is done once and only needs to be repeated for each treatment. The position used is important since the patient must be comfortable and feel supported during treatment. Sometimes, a device may be used to make it possible to repeat the position.
During simulation the radiation oncologist and the radiation treatment staff measure the body parts and may mark the skin with indelible marks so that the treatment is aimed at the same body part each day. These marks are referred to as a tattoo and do not wash off in the shower for the treatment period, but can be removed later.
Radiation Treatment Sessions
Radiation has the ability to effect tissues and cells by injuring the DNA in the cell nucleus. The effect of radiation, which does not make the body radioactive, is to either destroy the cell or alter its metabolism and hinder its ability to function normally. The cancer cells, which usually copy themselves in rapid succession, either stop growing or die more rapidly, after exposure to radiation. This process results in a decrease in the size of the tumor or elimination of the cancer cells. The treatment is not painful and most patients feel nothing, although they may hear sounds of the equipment turning on and off. The portions of the equipment that are visible to the patient are usually not the parts that generate the x-rays. The radiation oncologist determines the position for the treatment. Patients who receive whole body exposure may expect either to stand in a special apparatus or to be positioned lying down (either on the back or the abdomen). Protective shields are often used to cover the parts of the body that may not need treatment.
Patients may be in the treatment area for 20 to 30 minutes although the actual treatment may only take a minute or two. Sometimes the treatments are done on an outpatient basis and sometimes as an inpatient. During the treatment, the staff leaves the room and stands behind a shield so that they are not repeatedly exposed to radiation. They are within hearing distance and can maintain visual contact through a window or by using a closed-circuit television camera. Patients can talk to the staff during the treatment and report any discomfort or special needs.
Treatment Schedules
Treatments are usually scheduled Monday through Friday with a two day break on the weekend. This schedule continues for the entire treatment period and could last from two to six weeks. Schedules for treatment are based on prior clinical trials that tested dosage and treatment intervals. Patients are usually asked to remain on schedule and report any discomfort to the radiation oncologist so that decisions about schedule or treatment change are planned rather than spontaneous.
Immediate or Very Early Side Effects
Many patients anticipate side effects during the treatments and are surprised when there are very few. For others there can be side effects, but this depends on the dose, location, and duration of the radiation. Most of the side effects experienced by patients gradually go away after treatments are finished. Side effects that may be noted are increased fatigue, hair loss on the body part being treated, diarrhea if the abdomen is treated. Nausea, loss of appetite, skin irritation, and a sore mouth (mucositis) are also sometimes experienced. These side effects are usually a result of the radiation on tissue that contains rapidly dividing cells. This would include the hair follicles and the gastrointestinal tract lining. The cells also recover and so, some of the effects go away. If the radiation treatments are used prior to stem cell transplant (total body radiation) then more profound side effects may be expected. The therapist should inform patients about the course and effects of their particular treatments.
Long-Term Effects of Radiation Therapy
Some effects of radiation may not occur for months or years after treatment. These effects depend on the age of the patient and the dose and location of treatment. One long-term effect is the possible development of a secondary malignancy following the use of radiation. The physician usually addresses the chances of such a long-term effect during discussions before treatment.
Radiation in Combination
Some diseases, such as Hodgkin’s lymphoma, may be treated with combination therapy. This means a combination of chemotherapy and radiation therapy is used. For patients who receive this approach to treatment, chemotherapy may be administered in a cycle before the radiation therapy starts. The treatment approach is discussed with the patient prior to the start of treatment.
