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Radiation Oncology - A Patient's Guide

What is Cancer?

"Cancer" is a general term used to describe more than 200 diseases characterized by abnormal uncontrolled growth of cells that invade and destroy healthy tissue. Cancer can begin in any part of the body and may remain localized to one organ in the body or spread to other parts of the body.

The term "tumor" is used to describe a localized mass of cancer cells and is usually used to refer to a lump or mass seen or felt by physicians or visualized on x-ray studies. 

Each type of cancer is different. Some types of cancer tend to remain localized in one spot, while other cancers have the ability to spread quickly to other parts of the body. Not all patients with cancer are treated in the same way. 

It is important for doctors to determine the type and extent of the cancer. The term "stage" is used to describe the size of the cancer tumor mass and/or the extent to which the cancer cells have spread. Prior to determining a patient's treatment, physicians will usually recommend a series of medical tests (x-rays, blood tests, PET scan, biopsies, etc.) to determine the type and extent of cancer.

How is Cancer Treated?

The treatment of cancer is constantly undergoing change as we learn more about the disease and its treatment. Today, many patients with cancer can be cured of their disease.

There are three main types of cancer treatment which include surgery, radiation therapy, and chemotherapy. These treatments can be used alone or in any combination, depending on the type of cancer and its stage.

  1. Surgery

    Surgery is used to remove tumors from the body. When cancer cells are localized to one small area of the body and there is little risk that cancer cells will spread to other parts of the body, surgery may be used as the only form of treatment. In other situations, surgery may be used as a means to obtain tissue to diagnose the cancer or used in combination with one of the other forms of treatment.
  2. Radiation

    Therapy Radiation therapy is also an effective way of treating cancer. It may be used by itself or in conjunction with surgery or chemotherapy. Radiation therapy is often used in situations where complete surgical removal of the tumor is not possible or would cause serious deformity. Radiation therapy is often used in addition to surgery when there is evidence of localized spread of cancer cells beyond the area of the surgical resection. Radiation can be used to try to reduce the tumor size prior to surgery.
  3. Chemotherapy

    Chemotherapy is medication given to kill cancer cells and is administered under the direction of a medical oncologist. There are many different chemotherapy medications which can be used to treat cancer. Chemotherapy is usually used in situations where there is a significant risk of cancer cells spreading from the primary site to other locations in the body or when cancer cells have already spread. Chemotherapy is sometimes used simultaneously with radiation in order to enhance the effectiveness of both therapies.

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What is Radiation Therapy?

Radiation therapy is the use of high energy forms of radiation (such as x-rays, gamma rays, and electrons) in the treatment of diseases, especially cancer. Radiation has the ability to damage and kill cancer cells. Normal cells can also be affected by radiation. Most normal cells, however, have the ability to repair the damage done to them by radiation and are thus able to recover. 

The damage to cancer cells happens when they are exposed to the radiation. The death of cancer cells, however, may not occur immediately. The radiation damage to cancer cells often causes their death at the time when they attempt to grow and divide. This could be days or weeks after the radiation therapy has actually been administered.

Usually radiation treatments are given once daily over several weeks. This increases the likelihood of killing cancer cells and allows for the normal cells receiving radiation to repair themselves between treatments. 

There are several different types of machines that can be used to give radiation treatments. The most popular machine today is called a linear accelerator, which electrically manufactures high energy x-rays. These x-rays are similar to types of x-rays used to take an x-ray picture; however, the x-rays produced by a linear accelerator are much higher in energy. An older form of radiation therapy machine is a cobalt machine. Cobalt is a naturally occurring radioactive material that emits gamma rays which can be utilized in radiation therapy. Linear accelerators and cobalt machines are means of providing external radiation. That is, the radiation is produced in the machine and travels through air, entering the patient and absorbing the tumor cells and body tissues of the patient. 

In some situations, radioactive materials are implanted directly into the tumor. This is a specialized form of radiation therapy and will be discussed more completely in a separate handout.

What is a Radiation Oncologist?

Radiation oncology is the medical specialty that deals with the treatment of cancer with radiation. A radiation oncologist is a medical doctor who has received many years of special training in the study of cancer and in the use of radiation to treat cancer. Upon successful completion of an approved training program and successful completion of special examinations, a radiation oncologist can become board certified by the American Board of Radiology in the specialty of radiation oncology.

What Other Personnel Comprise the Radiation Oncology Team?

A radiation oncology center such as Greater Regional Cancer Center has highly trained personnel that work as a team to administer the radiation treatment. In addition to the medical doctors who direct and supervise the therapy, other members of the team include nurses, physicists, dosimetrists, and technologists. 

The radiation oncology nurse is an R.N. with special training in caring for cancer patients. The radiation physicist is a scientist with extensive training in monitoring the operation of the complex treatment machines and in overseeing the computerized planning of radiation dose distribution. A dosimetrist works with the radiation oncologist and physicist in designing specialized treatments for patients. A radiation therapist administers the daily treatments to the patients under the supervision of the doctors and operates the machines that deliver radiation therapy.

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What is Involved in Receiving Radiation Therapy?

  1. Consultation

    When a patient is referred to a radiation oncologist, the first meeting between the patient and the radiation oncologist is usually a consultation. This provides the radiation oncologist an opportunity to meet the patient, review the medical history and pertinent medical records, x-rays and laboratory tests. During the initial consultation, the radiation oncologist will also examine the patient. Before recommending any specific treatments, the physician needs to determine the type and extent of the cancer. The radiation oncologist will then discuss the case with the other physicians involved in the patient's care and treatment recommendations will be made.
  2. Treatment

    Planning Once the decision is made to use radiation therapy in the treatment of a patient's disease, then the treatment planning stage begins. The radiation oncologist will determine what area of the body needs to be treated - a decision often made based on various x-ray studies. A treatment planning simulation session will be scheduled. At the time of simulation, the radiation oncologist determines the size of the area to be treated and what energy of radiation will be used. The patient is measured and x-rays are taken on a machine called a simulator. The treatment planning simulation session takes approximately 40 minutes. During this time, the patient lies on a table. The skin overlying the area to be treated is marked with an ink-like fluid that will allow the patient to be positioned in the same exact way for each of the subsequent treatments. Usually, very small pinpoint tattoos are used so that the ink marks do not have to be kept on the skin for the entire course of the radiation treatments.

    Prior to beginning treatment, information obtained at the treatment planning simulation session is used to determine the dose of radiation to be administered. This often entails extensive computer planning and manufacturing custom made lead blocks to shield portions of the patient's body that do not need to be treated.
  3. Treatment

    Once radiation therapy treatment begins, it is typically administered once a day, five days a week. The radiation treatments last only about 15 - 20 minutes. One of the most important aspects of the treatment is for the patient to be positioned in exactly the same way each day. The treatments are completely painless; in fact, most patients experience no sensation at all while the treatment is being received.

What are the Side Effects of Radiation Therapy?

When radiation is administered to a patient, it is not possible to treat only the cancer cells. The surrounding normal tissues also receive some radiation exposure. The effect that the radiation has on these normal tissues accounts for the side effects of radiation therapy. The side effects of the therapy are very much dependent on what part of the body is being treated. For the most part, radiation therapy affects only parts of the body that are actually receiving the treatment. The radiation oncologist will carefully review the expected side effects with each patient prior to treatment.


Radiation therapy is an important component in the overall management of a patient with cancer. The radiation oncology team works closely with patients and their physicians to provide individualized care.

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Side Effects

  1. Every person is an individual. Radiation therapy side effects vary greatly from patient to patient. Some people have no side effects; others may develop mild to severe side effects.
  2. Side effects of radiation therapy are dependent on what part of the body is being treated and what dose of radiation is being given. For example, a patient receiving radiation treatments for a brain tumor would have very different side effects than a patient receiving radiation treatments for a tumor in the pelvis.
  3. Side effects represent the normal body tissue's response to radiation. Hence, the side effects depend on what normal tissues are in the vicinity of the tumor and are also receiving some of the radiation.
  4. No two patients are exactly alike. Not every one will experience all the same side effects to the same degree. Many patients will complete their course of radiation therapy with little or no significant side effects.
  5. Your doctor will review with you in detail the side effects that you may experience during your radiation therapy. These handouts will serve as a general guide to describe certain side effects and provide you with general instruction on how to handle them.
  6. It is important that you tell your doctor about any side effects that you experience during the course of your radiation therapy. Most side effects are normal body reaction to radiation and will require no specific medical treatments. In some circumstances, your doctor may prescribe medication to treat certain side effects depending on the symptoms.
  7. If you have any questions about the information provided in this handout, ask your doctor or nurse. We will be happy to answer your questions at any time.

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Glossary of Frequently Used Terms

Adjuvant therapy:

A treatment method used in addition to the primary therapy. Radiation therapy is often used as an adjuvant to surgery.


(al-oh-PEE-she-ah) Hair loss.


Loss of feeling or sensation resulting from the use of certain drugs or gases.


A medicine to prevent or relieve nausea or vomiting.

Benign tumor:

A growth that is not a cancer and does not spread to other parts of the body. 

Biological therapy:

Treatment by stimulation of the body's immune defense system.


The removal of a sample of tissue to see whether cancer cells are present. 


(brak-ee-THER-ah-pee) Treatment with radioactive sources placed into or very near the tumor or affected area; includes surface application, body cavity application (intracavitary), and placement into the tissue (interstitial). Sometimes this term is used interchangeable with "internal radiation therapy". 


A general term for more than 100 diseases characterized by uncontrolled growth of abnormal cells that can invade and destroy healthy tissues. 


Treatment with anticancer drugs.


(do-SIM-uh-trist) A person who plans and calculates the proper radiation dose for treatment. 

External radiation:

Radiation therapy that uses a machine located outside of the body to aim high-energy rays at cancer cells. 

Gamma rays:

Same as x-rays but from a different radioactive source.


A measurements of absorbed radiation dose; 1 gray=100 rad. 

Hyperfractionated radiation:

Division of the total dose of radiation into smaller doses that are given more than once a day.


A small container of radioactive material placed in or near a cancer.

Internal radiation:

A type of therapy in which a radioactive substance is implanted into or close to the area needing treatment. (See also interstitial implant and intracavitary implant.)

Interstitial implant:

A radioactive source placed directly into the tissue (not in a body cavity). 

Intracavitary implant:

A radioactive source placed in a body cavity such as the chest cavity or the vagina.

Intraoperative radiation:

A type of external radiation used to deliver a large dose of radiation therapy to the tumor bed and surrounding tissue at the time of surgery.

Linear accelerator:

A machine that creates high-energy radiation to treat cancers using electricity to form a stream of fast-moving subatomic particles. Also called megavoltage (MeV) linear accelerator or linac.


Cancerous (see cancer).


The spread of a cancer from one part of the body to another. Cells in the second tumor are like those in the original tumor. 


A doctor who is a specialist in the treatment of cancer.

Palliative therapy:

A treatment that may relieve symptoms without curing the disease.


An artificial replacement for a missing body part such as an artificial limb or breast form.


Short form for "radiation absorbed dose", a measurement of the amount of radiation absorbed by tissues (100 rad=1 gray).


Energy carried by waves or a stream of particles. Radiation oncologist: A doctor who specializes in using radiation to treat disease.

Radiation physicist:

A person trained to ensure that the radiation machine delivers the right amount of radiation to the treatment site.

Radiation therapist:

A person with special training who runs the equipment that delivers the radiation. Sometimes called a "radiation technologist."

Radiation therapy:

The use of high-energy penetrating rays or subatomic particles to treat disease. Types of radiation include x-ray, electron beam, alpha and beta particles, and gamma rays. Radioactive substances include cobalt, radium, iridium, and cesium. (See also gamma rays, brachytherapy, teletherapy, and x-ray.)


A physician with special training in reading diagnostic x-rays and performing specialized x-ray procedures.


See radiation therapy.


A process involving special x-ray pictures that are used to plan radiation treatment so that the area to be treated is precisely located and marked for treatment.


Treatment in which the radiation source is at a distance from the body. Linear accelerators and cobalt machines are used in teletherapy.

Treatment port:

The place on the body at which the radiation beam is aimed.


An abnormal mass of tissue. Tumors are either benign or malignant.


High-energy radiation that can be used at low levels to diagnose disease or at high levels to treat cancer.

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