Radiation Therapy
Radiation therapy uses high-energy rays to kill prostate cancer cells, shrink tumors, and prevent cancer cells from dividing and spreading. It is difficult to direct these rays only at the cancer cells. As a result, both cancer cells and healthy cells nearby may be damaged. Radiation therapy is not given all at once; it is usually given in small doses spread out over time. This potentially allows the healthy cells to recover and survive, while the cancer cells eventually die.
Radiation therapy may also be used for pain relief in prostate cancer that has spread to the bones (Stage M+) or that is no longer responding to hormonal therapy.
There are two ways in which the high-energy rays can be delivered. Radiation therapy involves either external beam radiation or a type of internal radiation called brachytherapy. These types of radiation therapy are discussed next.
External Beam Radiation Therapy
In external beam radiation therapy, a machine delivers the radiation in brief sessions, usually one session each weekday for several weeks. Many patients compare the treatments to having an X ray. The procedure itself is painless and lasts for just a few minutes.
Advancements in external beam radiation therapy have led to three methods of treatment that are described below. These developments may help reduce side effects and increase treatment success. Your physician can advise you on the right treatment for you.
3-Dimensional Conformal Radiation Therapy (3D-CRT)
One type of external beam radiation therapy is 3-dimensional conformal radiation therapy, in which computers are used to identify the location of the prostate and 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 while the radiation is aimed at the cancer.
When the patient wears the body mold during the treatments, the radiation beams can be aimed more accurately to target the entire prostate gland. The idea is to be able to direct a high dose of radiation only toward the prostate, while reducing the amount of radiation that the surrounding healthy 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 type of radiation therapy. This technique is similar to 3-dimensional conformal radiation therapy, except that it uses protons to produce the radiation beam. Protons are microscopic particles that produce energy in the form of a radiation beam. Using proton beams can help spare healthy tissue.
Intensity Modulated Radiation Therapy (IMRT)
Intensity Modulated Radiation Therapy (IMRT) is another form of external beam radiation therapy. Computed tomography (CT) is used to create a 3-D picture of the prostate and surrounding organs so the radiation can be delivered only to the prostate gland.
IMRT is more precisely targeted than 3-dimensional conformal radiation therapy (3D-CRT). IMRT uses many thinner beams to precisely target the prostate gland and spare other nearby organs from radiation. Therefore, IMRT allows for an increased radiation dose to be delivered to the prostate gland, potentially resulting in better elimination of cancer cells. IMRT is administered in short sessions five times a week for approximately seven weeks.
Advantages of External Beam Radiation Therapy: Prostatectomy is usually avoided by using external beam radiation therapy. External beam radiation therapy may optimally treat prostate cancer in its early stages and may help reduce the severity of cancer in later stages. It rarely causes loss of urinary control.
IMRT is a technological advancement in the use of external beam radiotherapy. It allows doctors to treat tumors with a higher dose of radiation, retreat cancers that have previously been treated with radiotherapy, and more safely treat tumors that are located close to other organs. IMRT also reduces the amount of radiation administered to nearby organs compared to other forms of external beam radiotherapy, thereby decreasing side effects.
The techniques mentioned above are promising in terms of less chance for adverse effects and greater chance for success than older methods of external beam radiation therapy.
Disadvantages of External Beam Radiation Therapy: External beam radiation therapy can cause a variety of side effects. Many of these 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.
Development of impotence generally does not occur immediately after radiation treatment, but instead may occur over a period of one or more years1. It can be a permanent side effect. This is especially important for the younger patient to consider when thinking about different treatment options.
Radiation therapy may be inconvenient because patients need to make frequent visits to the hospital or clinic for treatment (usually 5 times per week for about 2 months).1
If the prostate cancer doesn't respond to or progresses with radiation therapy, the cancer cannot be retreated with radiation. Surgical removal of the prostate is complicated after radiation, but may sometimes be performed if radiation therapy fails.
Finally, some types of radiation therapy mentioned above may not be available at all radiation therapy centers.
Your doctor and local radiation center will be able to tell you the specific types of treatment offered at your center.
Brachytherapy
In brachytherapy (sometimes called interstitial radiation therapy or "radioactive seeds"), the radiation comes from tiny, radioactive seeds inserted directly into the prostate. Specialized equipment is used to view the tumor so the surgeon can place the seeds correctly. The seeds are inserted into the tumor during a minor surgical procedure under some form of anesthesia, so brachytherapy is usually performed as an outpatient procedure. The seeds are too small to be felt by the patient and do not cause any discomfort. The picture shown here depicts one type of seed used during brachytherapy. You will notice that the seeds are very small.
The seeds used in brachytherapy can be very small. A type of palladium seed is shown on top of the penny.
Brachytherapy often allows the doctor to use a higher dose of radiation than is possible with external beam radiation. The seeds give off rays continually for hours, weeks, months, or up to a year, and some 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. The seeds used during brachytherapy contain different radioactive substances that may include radium, iridium, cesium, phosphorus, iodine, and palladium. Brachytherapy, however, does not make the patient radioactive.
By using brachytherapy, radiation is placed as close as possible to the cancerous cells so that less of the normal tissue is exposed to the radiation.
Because it is designed to target the cancerous cells and not harm the surrounding area, brachytherapy is usually not recommended when the cancer has spread beyond the prostate gland. Brachytherapy may be used alone or can be combined with external beam radiation therapy. Thus far, some studies show that brachytherapy for the treatment of prostate cancer that has not spread beyond the prostate gland has similar effectiveness when compared to radical prostatectomy and advanced EBRT methods.
High-dose Rate Brachytherapy
High-dose rate brachytherapy is a form of brachytherapy 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.
Advantages of Brachytherapy: Brachytherapy has shown some promising results. In general, there are often fewer complications with brachytherapy than with extensive surgeries like prostatectomy.
The brachytherapy procedure itself is well tolerated in most cases. This type of therapy typically requires fewer visits to the hospital or doctor's office than other treatments for prostate cancer.
Disadvantages of Brachytherapy: Temporary side effects may include diarrhea, rectal pain, and burning in some patients.
Brachytherapy has been associated with impotence, urinary incontinence, and bowel problems.
As mentioned earlier, seed insertion usually is not an option for treatment of prostate cancer that has spread beyond the prostate gland.
Injectable Radioactive Compounds
Prostate cancer that has spread to the bones often causes pain. There are various options available to treat this pain. As mentioned previously, external beam radiation therapy can be given to treat certain localized spots of bone pain. An alternative form of radiation therapy is an injectable radioactive compound. There are several types of these radioactive compounds that are given intravenously. They work more generally throughout the entire body, but not on every type of tumor.
References
- American Cancer Society. Prostate Cancer Detailed Guide. Available at: http://www.cancer.org/docroot/CRI/content/
CRI_2_4_7x_CRC_Prostate_Cancer_PDF.asp. Accessed April 14, 2008.
Styrofoam is a registered trademark of The Dow Chemical Company.
This information is intended for US consumers only.