Radiotherapy or radiation therapy is the general term for the use of radiation in the treatment of disease. Radiotherapy uses ionizing radiation to kill harmful cells in the body. Ionizing radiation can come from many sources, such as x-rays, gamma rays, or proton beams.
When used for cancer treatments, radiation kills cancerous cells and shrinks tumors. Radiation therapy can be used in combination with other treatments, such as chemotherapy, hormone therapy, or surgery, or it can be used alone in the treatment of the disease. The treatment approach relies on the type of cancer and the stage of the disease.
Radiation therapy has been used successfully in the treatment of lymphomas for many years. Lymph cells are incredibly sensitive to radiation, which is why this treatment is so effective. To treat lymphomas, doctors will expose a patient to radiation from an outside source, usually a machine. This external-beam radiation therapy will target cancerous cells wherever it is applied.
Radioimmunotherapy combines radiotherapy with monoclonal antibody therapy. Though it was developed in the 1980's, radioimmunotherapy is just now beginning to gain widespread acceptance. In the United States, it has been approved by the FDA for treatment of certain refractory and relapse NHL's. Zevalin® has been approved by the FDA as a first-line radioummunotherapy treatment for certain types of follicular lymphomas.
When a patient undergoes radiation therapy, s/he has a team of knowledgeable and experienced doctors. This group consists of a radiation oncologist, a radiation physicist, a dosimetrist, and a radiation therapy nurse.
The radiation oncologist reviews a patient's medical records, scans, blood tests, and any other pertinent information. They conduct a physical exam on the patient as well. Based on their examinations, the radiation oncologist will estimate what areas of the body need radiotherapy. These areas are called the treatment fields or ports. In lymphomas, the treatment fields are usually in the neck, torso, and groin, where the highest concentrations of lymph nodes are.
To accurately determine treatment fields, the radiation oncologist may have a lymphoma patient perform a simulation. During a radiotherapy simulation, the oncologist uses low-dose x-rays to examine the patient's internal organs and narrow their estimated treatment fields. These simulations can take an hour or two, so the patient may need to be sedated to prevent unwanted movement.
Once the radiation oncologist has determined the patient's treatment fields, they will consult with the radiation physicist and dosimetrist to determine the dose of radiation. Together, these three professionals pick a dose appropriate for the type of lymphoma and the stage of the disease. This dose is then divided up over the treatment period, which can last for several weeks.
As with chemotherapy, radiation therapy can cause significant side effects.
Photo from NCI