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Types of Cancer > Prostate Cancer > Prostate Cancer Basics
Radiation Therapy
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Copyright 1994-2004 © Trustees of the University of Pennsylvania
Last Modified: November 1, 2001
Radiation therapy uses high-energy rays to kill prostate cancer cells, shrink tumors, or prevent cancer cells from dividing and spreading. It is nearly impossible to direct these rays only at the cancer cells. As a result, they may damage both cancer cells and healthy cells nearby. Radiation doses are usually small and spread out over time. This allows the healthy cells to recover and survive, while the cancer cells eventually die. Radiation therapy is usually used when prostate cancer has not spread beyond the prostate (Stages T1-T2). It can help prevent the cancer from spreading further. Like surgery, radiation therapy works best when the cancer is located in a small area. In early stages of prostate cancer, radiation therapy may cure the disease. Radiation therapy also may be used alone or in combination with hormone therapy when cancer cells have spread beyond the prostate to the pelvic area (Stages T3-T4) and for pain relief in prostate cancer that is no longer responding to hormone therapy and has spread to the bones (Stage M+).
There are two ways in which the high-energy rays can be delivered. Radiation therapy involves either external beam radiation therapy (EBRT) or a type of internal radiation called brachytherapy. These types of radiation therapy are discussed below.
External beam radiation therapy
In external beam radiation therapy, the rays are delivered by a machine, and the radiation is given in brief sessions, usually one session each weekday for several weeks. Many patients compare the treatments to having an x-ray. The procedure is painless and lasts for just a few minutes. External beam radiation therapy may be given alone or in combination with hormone therapy.
Recent advances in radiation therapy include two new methods of treatment. These developments may help reduce side effects and increase treatment success. It is important to remember, however, that newer treatments are often considered experimental until they can be shown to have the same success rate as more standard forms of therapy. In addition, these newer types of therapy may not be available at all radiation centers. Your physician can advise you on the right treatment for you.
3-dimensional conformal radiation therapy (3D-CRT)
In 3-dimensional conformal radiation therapy (3D-CRT), high-tech computers are used to identify the location of the cancer inside the prostate gland. The next step involves the creation of a special protection device that the patient wears during the treatments. This device is similar to a body cast, but it is molded out of styrofoam and helps to keep the body still during treatment and to aim the radiation beams more accurately to target the entire prostate gland. The idea is to be able to direct a high dose of radiation toward only the cancer cells, while reducing the amount of radiation that the surrounding noncancerous areas receive. If the healthy tissue can be spared from the effects of radiation, side effects should be lower and therapy success higher.
Conformal proton beam radiation therapy
Conformal proton beam radiation therapy is another new type of radiation therapy. This technique is similar to 3D-CRT, except that it uses protons to produce the radiation beam. Protons are microscopic particles that produce energy in the form of a radiation beam. The proton beams can pass through healthy tissue without damaging it, while still aimed at cancerous tissue.
| Advantages:
Major surgery can usually be avoided by using radiation therapy.
Radiation therapy may cure prostate cancer in its early stages
and may help extend life in later stages. It rarely causes
loss of urinary control, and other side effects like impotence
occur less often than with surgery. The newer techniques mentioned
above look promising in terms of less chance for adverse effects
and greater chance for success. |
|
| Disadvantages:
Radiation therapy can cause a variety of side effects. Most
of these are minor and disappear after therapy stops. These
side effects include tiredness, skin reactions in the treated
areas, frequent and painful urination, upset stomach, diarrhea,
and rectal irritation or bleeding. There is a chance of some
permanent side effects. Bowel function may not return to normal
even after treatment is complete. When an external machine
provides radiation therapy, impotence may develop up to 2
years later in some patients and can be a permanent side effect.
It is especially important for the younger patient to consider
this when thinking about different treatment options. Finally,
the newer types of radiation therapy, such as 3D-CRT and EBRT,
may not be available at all radiation therapy centers. Your
physician and local radiation center will be able to tell
you the specific types of treatment offered at your center.
|
Brachytherapy or "seeds" (interstitial radiation therapy)
In brachytherapy
(also called seeds or interstitial radiation therapy), the rays
come from tiny radioactive seeds inserted directly into the prostate.
Brachytherapy may be used by itself or can be combined with EBRT.
The seeds are too small to be felt by the patient and do not cause
any discomfort. They are inserted into the cancer during a surgical
procedure after the patient has been put to sleep using a local
or general anesthetic.
Specialized equipment like CT scans, ultrasound, and MRI help the
surgeon to place the seeds correctly. The seeds give off rays continuously
for weeks, months, or up to a year, and can remain safely in place
for the rest of a person's life. The amount of time that the seeds
remain radioactive depends on the dose and what type of radioactive
material is used.
In brachytherapy, radiation is placed as close as possible to the
cancerous cells so that less of the normal tissue is exposed to
the radiation. Interstitial radiation therapy often allows the physician
to use a higher dose of radiation but for a shorter length of time
than is possible with external radiation. The seeds used during
brachytherapy contain different radioactive substances that may
include radium, iridium, cesium, phosphorus, iodine, and palladium.1
Brachytherapy, however, does not make the patient radioactive.
Interstitial radiation therapy is usually performed within a hospital, and you may need to stay there for a few days or longer. Below is a picture of one type of seed used during brachytherapy. You will notice that the seeds are very small. Because it is designed to target the cancerous cells and not harm the surrounding area, brachytherapy is rarely recommended when the cancer has spread beyond the prostate gland.
High-dose rate brachytherapy
High-dose rate brachytherapy is a newer form of interstitial radiation treatment involving seeds that are placed only temporarily. These seeds stay in place for less than a day and contain more radioactive material than the seeds that stay in place longer. This type of brachytherapy may even be performed in a clinic as an outpatient visit and may not require hospitalization.
 |
The seeds used in brachytherapy can be very small. A type of palladium seed is shown on top of the penny. |
Strontium 89
Strontium 89, also called Metastron,®* is another form of radiation therapy. It is delivered by injection and is used to control bone pain in patients with metastasized (Stage M+) prostate cancer that no longer responds to hormone therapy. Strontium 89 radiation goes directly to the bone to kill cancer cells and may give dramatic pain relief to many patients with discomfort. Since this type of radiation will "seek out" bones affected with cancer, it can be quite effective. Strontium 89 can also be combined with EBRT if necessary.
| Advantages:
Brachytherapy has shown some promising early results.2
In general, there are often fewer complications with brachytherapy
than are seen with the more extensive surgeries.3
The procedure itself is generally painless and, in many cases,
the patient feels less pain after the treatment than with
other surgery. Brachytherapy requires fewer visits to the
hospital or physician's office than other treatments. In fact,
the newer types of brachytherapy, like high-dose rate brachytherapy,
usually involve very little discomfort. New injectable radioactive
compounds, such as those containing radioactive strontium,
can provide pain relief from cancer that has spread to the
bone. These new compounds have fewer side effects than the
radioactive phosphorous compounds that have been available
for many years. |
|
| Disadvantages: Clinical trials are still under way to determine the effectiveness of radiation therapy.4 Brachytherapy has been associated with impotence, urinary incontinence, and bowel problems. Diarrhea and rectal pain and burning can be experienced in some patients. In addition, these side effects may not be easy to treat. In general, internal radiation therapy has side effects that are similar to EBRT in general but with a few important differences. Brachytherapy causes impotence less often than surgery or EBRT; however, it may be associated with decreased white blood cell and platelet counts. As mentioned earlier, seed insertion is usually not an option for treatment of prostate cancer that has spread beyond the prostate gland. |
References
1. National Institutes of Health. Cancer Facts:Radiotherapy.
Available at http://cis.nci.nih.gov/fact/7_1.htm.
Accessed April 23, 2001.
2. Frydenberg M, Stricker PD, Kaye KW. Prostate cancer diagnosis
and management. The Lancet. 1997;349:1681-1687.
3. Columbia/HCA Healthcare Corporation. Prostate Brachytherapy:
A "New" Treatment Option for Prostate Cancer Patients.
Available at: http://www.medtropolis.com/healthcontent.asp?page=/hic/prostate/crs/index.
4. Coley CM, Barry MJ, Fleming CM, et al. Early detection of prostate
cancer. Part II: estimating the risks, benefits, and costs. Annals
of Internal Medicine. 1997;126:468-479.
| Copyright 1994-2004 © Trustees of the University of Pennsylvania |