Munson Health
 
Radiation Therapy for Cancer Treatment

Back to Document

by Calvagna M
 
Radiation therapy is the use of penetrating beams of high-energy waves or streams of particles called radiation to treat disease. Radiation has been used to treat cancer since the late 19th century. In fact, the first successful radiation treatment for cancer was reported in 1898.
In its earliest state, radiation was given in single, large doses, which caused many complications. By 1940, doctors had begun dividing the total dose of radiation into several smaller doses. This process is known as fractionation of the dose. Fractionation is very important because it allows the oncologist to destroy tumor cells, while allowing normal tissues to repair the radiation damage.
In the last 50 years, technology has allowed for great advances in radiation therapy, including deeper penetration of the radiation and less scatter to healthy tissues. Currently, there exists a delicate balance between using radiation to treat cancer cells and minimizing its adverse side effects on the body's normal cells.

What Is Radiation Therapy Used For?

Some factors affecting how well radiation therapy will work include the following:

What Are the Types of Radiation Therapy?

External Radiation Therapy
A CT scan is a type of x-ray that uses a computer to produce cross-sectional images of the inside of the body. An MRI scan uses magnetic waves to produce images of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces 2D and 3D pictures. A barium enema is a rectal injection of barium, a substance that coats the lining of the colon and rectum. It is done before x-rays are taken in order to create better x-ray images.
If you receive external radiation therapy, you will go to the hospital or clinic each day for treatment. Usually, treatments are given 5 days a week for 2 to 8 weeks. The total dose of radiation and the number of treatments necessary will depend on the size, location, and type of cancer you have, as well as your general health and other medical treatments you may be having. This procedure is like having an x-ray. Actual treatment time (the time you are receiving radiation) ranges from 2 to 5 minutes.
Hyperfractionated External Radiation Therapy
Radiation is usually given once a day with a dose based on the type and location of the tumor. In hyperfractionated radiation therapy, the daily dose is divided into smaller doses and given several times a day (usually twice a day). Treatments are separated by 4 to 6 hours.
Hyperfractionation is used in the treatment of head and neck cancers, some lung cancers , and in a situation where a patient has already had radiation therapy and needs more to that same area. Other cancer sites have not been conclusively shown to respond to radiation given more often than once daily.
Delivery of External Radiation Therapy
Different types of machines are used to deliver the radiation. The higher the energy produced by the machine, the greater the depth of penetration. In addition, there is less radiation scatter with higher energies.
This table explains the two main types of treatment machines.
MachineTreatment BeamCharacteristicsUse
OrthovoltageX-rays with 150-500 kilovolts (kV) of energy Low-level energy
Superficial treatment scatter of radiation beam
Superficial skin cancer
MegavoltageX-rays and electrons with 1-18 million volts of energy Deeper penetration below skin level
Less scatter
All tumors other than skin cancer
At the end of the treatment regimen, the tumor site often gets an extra dose of radiation, called a boost.
Internal Radiation Therapy
Internal radiation therapy, also called brachytherapy, places the radiation source as close as possible to the cancer cells. Radioactive material, sealed in a thin wire, catheter, or tube, is placed directly into the affected tissue. This method concentrates the radiation on the cancer cells and minimizes the radiation damage to the normal tissue nearby.
The radioactive substances used for internal radiation therapy include the following:
  • Cesium
  • Iridium
  • Iodine
  • Phosphorus
  • Palladium
The type of implant and how it is placed depends on the size and location of the tumor. Methods include the following:
  • Interstitial radiation—The implant is placed directly into the tumor via catheters, seeds, or capsules. This is commonly used for prostate cancer.
  • Intracavitary radiation—Commonly used for cervical cancer, the implant is placed in special applicators inside a body cavity.
  • Intraluminal radiation—Commonly used for lung or esophageal cancer , the implant is placed in special applicators inside a body passage or lumen.
  • Surface brachytherapy—The implant is placed in or against the tumor. This is commonly used for skin cancer or melanoma of the eye.
Implants may be removed after a short time or left in place permanently. When left in place, the implants become non-radioactive in a short time. For the placement of most types of implants, you will need to be in the hospital.
Indications for internal radiation therapy include cancers of the head and neck, lung, breast, uterus, thyroid, cervix, rectum, bladder, and prostate. It is sometimes given in combination with external radiation therapy.
Intraoperative Radiation
Intraoperative radiation combines surgery and radiation therapy. During surgery, after as much of the tumor as possible is removed, a large dose of radiation is given directly to the tumor bed and nearby areas. This therapy is sometimes given in combination with external radiation therapy.
Intraoperative radiation is used to treat locally advanced abdominal cancers such as stomach, pancreatic, colorectal, and retroperitoneal sarcomas.
Photodynamic Therapy
In photodynamic therapy (PDT), photosensitizers, or light-sensitive molecules, are injected into the bloodstream and absorbed by cells throughout the body. These agents remain in cancer cells longer than in normal cells. When the cancer cells are exposed to laser light, the photosensitizers are activated and form oxygen radicals that affect cell membranes, the cytoplasm, and the DNA. This results in cell damage and death. PDT causes minimal damage to healthy tissue, but the laser light used in PDT cannot pass through more than 3 centimeters of tissue.
PDT is mainly used to treat tumors on or just under the skin or on the lining of internal organs. Currently, PDT is used in the treatment of skin, lung, and esophageal cancers as well as superficial cancers of the bladder, head, and neck.
In addition, PDT is used for bone marrow purging . Bone marrow used for autologous transplantation must be relatively free of cancer cells. Before transplantation, the harvested marrow is often treated with PDT in a process known as "purging" to get rid of cancer cells.
Hyperthermia With Radiation Therapy
In hyperthermia, body tissues are exposed to high temperatures (up to 106°F) to damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation. Methods include the following:
Local hyperthermia —Heat is applied to a small area, usually the tumor itself, either externally or internally. If heated externally, high-frequency sound waves are aimed at the tumor using a device (like an ultrasound machine) outside the body. Internal heating can be done by inserting sterile probes that are either heated or filled with warm water, implanted microwave antennae, or radiofrequency electrodes.
Regional hyperthermia —Heat is applied to an organ or a limb. This can be done with magnets or other devices that produce high energy. Or, blood can be removed, heated, and returned to the affected region.
Whole-body hyperthermia —Heat is applied to the entire body. This is used for metastatic cancer that has spread throughout the body. Warm-water blankets, hot wax, inductive coils, or thermal chambers are used to raise body temperature.

What Adverse Effects Can Occur With Radiation Therapy?

Blood Abnormalities
During radiation therapy, blood levels may be monitored, particularly if chemotherapy is also being delivered, or if a large part of the body is being irradiated. For many sites treated with radiation, there is no reason to get blood samples, unless you begin to feel poorly and the doctor wants to determine if low blood counts are to blame. If a blood test shows significant bone marrow effects, your doctor may wait until your blood counts increase before continuing treatment. Blood transfusions are sometimes necessary.
Hair Loss
Radiation therapy can cause hair loss, also known as alopecia . Hair loss occurs only in the area being treated with radiation. If you receive radiation to your head, you may lose some or all of the hair on your scalp. The amount of hair that grows back depends on how much and what kind of radiation you received. Some people find that when their hair grows back, the color or texture may be slightly different.
Although not life-threatening, hair loss can be upsetting. Many people buy a wig or hairpiece, or use hats or scarves, to cover their heads. If you buy a wig because of cancer treatment, it is a tax-deductible expense and may be covered in part by health insurance.
Loss of Appetite
Loss of appetite can be a symptom of the cancer itself, as well as a side effect of cancer treatment. It is not unusual to lose one or two pounds a week during radiation treatment. You will be weighed weekly to monitor your weight.
Many small meals, rather than three large ones, can help make eating seem less overwhelming. Ask your doctor for a referral to a registered dietitian (RD) to assist you in setting up a diet plan that helps you maintain weight. In addition, medications to increase your appetite are available. If it is painful to chew and swallow, you may want to try a powdered or liquid diet supplement. It is crucial that you get enough calories and protein so that your body has enough energy to fight the cancer. Studies have found that people who eat well cope better with their cancer and its treatment.
 

References


Hyperthermia in cancer treatment. National Cancer Institute website. Available at: http://cis.nci.nih.gov/fact/7%5F3.htm . Accessed December 1, 2002.


Otto SE. Oncology Nursing. 4th ed. St. Louis, MO: Mosby, Inc; 2001: 606-637.


Photodynamic therapy. National Cancer Institute website. Available at: http://cis.nci.nih.gov/fact/7%5F7.htm . Accessed December 1, 2002.


Radiation therapy and you: a guide to self-help during cancer treatment. National Cancer Institute website. Available at: http://www.cancer.gov/ . Accessed November 25, 2002.

 

Revision Information