What is radiation therapy?

Radiation therapy is the use of high-energy x-rays to damage cancer cells and stop them from growing. Radiation done after surgery can kill cancer cells that may not be seen during surgery. Radiation may also be done:

• prior to surgery to shrink the tumor.
• in combination with chemotherapy.
• as a palliative treatment (therapy that relieves symptoms, such as pain, but does not alter the course of the disease).

There are several ways to deliver radiation therapy. For more detailed information about the radiation treatment recommended for a specific type of cancer, please refer to another section of this website- cancer information, by type.

External Radiation (external beam therapy)
The goal of radiation therapy is to get a high enough dose of radiation into the body to kill the cancer cells while sparing the surrounding healthy tissue from damage. Several different radiation therapy techniques have been developed to accomplish this. Depending on the location, size and type of your tumor or tumors, you may receive one or a combination of these techniques. Your cancer treatment team will work with you to determine which treatment and how much radiation is best for you.

During external beam radiation therapy, a beam of radiation is directed through the skin to a tumor and the immediate surrounding area in order to destroy the main tumor and any nearby cancer cells. To minimize side effects, the treatments are typically given every day for a number of weeks.

The radiation beam comes from a machine located outside of your body that does not touch your skin or the tumor. Receiving external beam radiation is similar to having an X-ray taken. It is a painless, non-invasive procedure. The machine used to deliver external beam radiation therapy is called a linear accelerator. It produces a beam of high-energy X-rays or electrons. Using sophisticated treatment planning software, your radiation oncology treatment team plans the size and shape of the beam, as well as how it is directed at your body, to effectively treat your tumor while sparing the normal tissue surrounding the cancer cells. Several different types of external beam therapy are discussed below. Each is used for particular types of cancer.

• Three-Dimensional Conformal Radiation Therapy (3D-CRT)

Tumors usually have an irregular shape. Three-dimensional conformal radiation therapy (3D-CRT) uses sophisticated computers and computer assisted tomography scans (CT or CAT scans) and/or magnetic resonance imaging scans (MR or MRI scans) to create detailed, three-dimensional representations of the tumor and surrounding organs. Your radiation oncologist can then shape the radiation beams exactly to the size and shape of your tumor. The tools used to shape the radiation beams are multi-leaf collimators or custom designed shielding blocks. Because the radiation beams are very precisely directed, nearby normal tissue receives less radiation exposure.

• Intensity Modulated Radiation Therapy (IMRT)

Intensity modulated radiation therapy (IMRT) is a specialized form of 3D-CRT that allows radiation to be more exactly shaped to fit your tumor. With IMRT, the radiation beam can be broken up into many “beamlets,” and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the exact amount of radiation that is received by normal tissues that are near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, increasing the chance of a cure.

• Image-Guided Radiation Therapy (IGRT)

For some patients, radiation oncologists use image-guided radiation therapy (IGRT) to help them better deliver the radiation dose to the cancer. Normal structures and tumors can move between treatments due to differences in organ filling or movements while breathing. IGRT is conformal radiation treatment guided by imaging equipment, such as CT, ultrasound or stereoscopic X-rays, taken in the treatment room just before the patient is given the radiation. All patients first undergo a CT scan as part of the planning process. The digital information from the CT scan is then transmitted to a console in the treatment room to allow doctors to compare the earlier image with the images taken just before treatment. During IGRT, doctors “fuse” these images to see if the treatment needs to be changed. This allows doctors to better target the cancer while avoiding nearby healthy tissue. In some cases, doctors will implant a tiny piece of material called a fiducial marker near or in the tumor to help them localize the tumor during IGRT.

Internal Radiation (brachytherapy, implant radiation)
Radiation is given inside the body as close to the cancer as possible. Substances that produce radiation, called radioisotopes, may be implanted directly into the tumor. Depending upon the type of cancer, internal radiation treatment may involve either Low Dose Radiation (LDR) or High Dose Radiation (HDR).

• An example of LDR would be the treatment recommended for prostate cancer. Radioactive seeds, each about the size of a grain of rice, are placed into the prostate. These emit low energy x-rays which destroy the cancer cells. Since the radiation emitted from each seed does not normally reach nearby organs, it is generally a safe form of radiation therapy. Radiation oncologists at Huntington Hospital are among the most experienced in the country using Cesium-131 for prostate cancer. Additional information on this isotope can be found at www.isoray.com.

HDR treatment is recommeded for some types of  breast, skin, rectal, and certain gynecologic cancers.

• HDR treatment for skin cancer patients is available at Huntington Hospital. Developed by Huntington radiation oncologist Maged Ghaly, MD, this revolutionary technique uses a small radioactive source in a special applicator which is applied directly to the skin lesion. The outcome is equivalent to surgery, but unlike surgery it is achieved non-invasively and without side effects or scarrring. Any lesion smaller than three centimeters (about one inch) can be treated. Most patients require eight to ten treatments which are spaced out over a few weeks.
• Endorectal brachytherapy, a new HDR treatment for rectal cancer patients, is available at Huntington Hospital. Usually an outpatient procedure, the treatment radiation is delivered via a plastic applicator which is placed in the rectum. The applicator is scored with channels. Only those channels that will be in direct contact with the tumor are loaded with radiation to deliver the maximum dose to the cancer while sparing the rectum walls and other internal organs. Studies have shown that this treatment doubles the patient’s chance of undergoing anal preservation surgery and reduces the odds of the patient requiring a permanent colostomy. The treatment also minimizes the side effects of traditional external beam radiation.

• Radiation oncologists at Huntington Hospital also offer radioactive seed implantation in the treatment of breast cancer. Mammosite®, a form of HDR, cuts radiation treatment time from six weeks to one week while minimizing treatment side effects. Studies suggest that it is as effective as traditional radiation of the breast at preventing a recurrence of cancer.
  
  (Click here for more information about Mammosite radiation therapy.)
  

A radiation oncologist will plan your radiation treatment based on your medical history, a physical examination, pathology and laboratory reports, and any surgeries you may have had. Your skin will be marked with ink that must stay on for the course of your treatments. These markings assure that the radiation will be given to the exact area requiring treatment.

Side effects of radiation therapy:

Today, the side effects of radiation therapy are better controlled due to the advancement of technology. Huntington Hospital’s linear accelerator delivers radiation to cancer cells with the highest level of precision.

As each person's individual medical profile and diagnosis is different, so is his/her reaction to treatment. Side effects may be severe, mild, or absent, and are usually specific to the area treated. Be sure to discuss with your cancer care team any/all possible side effects of treatment before the treatment begins. Possible side effects that may occur during or following radiation therapy include:

• fatigue (especially during the later weeks of treatment)
• skin problems in the treated area, including soreness, itching, peeling, and/or redness. Toward the end of treatment, the skin may become moist and weepy.
• decreased sensation in the treatment area

In most cases, the effects of radiation on the skin are temporary and the skin involved in the treated area will heal upon completion of treatment.

A radiation oncologist carefully monitors the intensity and length of each treatment, and the area being treated. In addition, you will have regular physical examinations during the course of your treatments.

© Copyright 2008 by Huntington Hospital