Radiation therapy for prostate cancer
Radiation therapy uses high-energy rays or particles to destroy cancer cells. It is usually used to treat prostate cancer. Your healthcare team will consider your personal needs to plan the type and amount of radiation, and when and how it is given. You may also be given hormonal therapy together with radiation therapy.
Radiation therapy is given for different reasons. You may have radiation therapy to:
- destroy cancer cells in the body
- destroy cancer cells left behind after surgery to reduce the risk that cancer will come back (recur) (called adjuvant therapy)
- relieve pain or control the symptoms of advanced prostate cancer (called palliative therapy)
- treat cancer that comes back after surgery (called salvage radiation therapy)
The following types of radiation therapy are most commonly used to treat prostate cancer.
External beam radiation therapy
During external beam radiation therapy, a machine directs radiation through the skin to the tumour and some of the tissue around it. Lymph nodes in the pelvis may also be treated with external beam radiation therapy.
External beam radiation therapy may be used as the main treatment for prostate cancer. It may also be given after surgery if the tumour has grown close to or through the capsule of the prostate.
Sometimes external beam radiation therapy is given to shrink a prostate tumour to relieve urinary problems. It can also help relieve pain caused by cancer that has spread to bones (called bone metastases).
Conformal radiation therapy
Conformal radiation therapy uses a special device that can change the shape of a radiation beam so it better fits (conforms to) the shape and size of the tumour. This means that more radiation is directed at the tumour and there is less radiation damage to normal tissues around the tumour.
The following types of conformal radiation therapy may be used to treat prostate cancer.
3-dimensional conformal radiation therapy (3-D CRT) delivers radiation to the tumour from different directions. CT images of the prostate and surrounding area are used to help target the radiation beam to the tumour. The radiation beams are all the same strength.
Intensity-modulated radiation therapy (IMRT) is a newer form of 3-D CRT. It uses CT images and many radiation beams of different strengths to deliver higher doses of radiation directly to a tumour. IMRT uses specialized equipment so it might not be available at all cancer treatment centres in Canada.
Stereotactic radiation therapy
Stereotactic radiation therapy is a type of external beam radiation therapy. Stereo means 3-D and tactic means to probe. Stereotactic radiation therapy allows radiation beams to be given to a very specific area. It delivers large doses of radiation in each dose and the treatment is usually given over a few days.
Gamma Knife, CyberKnife and Tomotherapy are brands of machines that may be used in stereotactic radiation therapy to treat prostate cancer.
Proton beam radiation therapy
Proton beam radiation therapy is also called charged particle radiation therapy. It uses high-energy (charged) proton particles instead of x-ray beams. Protons deliver a higher dose of radiation but cause less damage to nearby tissues than conventional external beam radiation therapy because they can be aimed more precisely at the tumour. Proton beam radiation therapy is not widely available in Canada.
Brachytherapy is internal radiation therapy. It uses an implant that contains a radioactive material called a radioactive isotope. The implant is placed right into the tumour or very close to it. The radiation kills the cancer cells over time.
If you had transurethral resection of the prostate (TURP) and the surgeon had to remove a large amount of prostate tissue, you may not be able to have brachytherapy. This is because men who have had this procedure have a higher risk of developing urinary incontinence and erectile dysfunction.
External beam radiation therapy and brachytherapy may both be used to treat prostate cancer that has a high risk of coming back after treatment.
Low-dose-rate (LDR) brachytherapy
LDR brachytherapy for prostate cancer uses a permanent implant to deliver continuous low doses of radiation over several weeks or months. Doctors often use a transrectal ultrasound (TRUS) to guide them when they place the implant. Iodine-125 or palladium-103 are the radioactive substances most commonly used for LDR brachytherapy to treat prostate cancer. Special safety precautions are taken to make sure other people aren’t exposed to radiation.
LDR brachytherapy is mainly used to treat early stage prostate cancer that is growing slowly and has a low risk of coming back after treatment.
High-dose-rate (HDR) brachytherapy
HDR brachytherapy for prostate cancer uses a temporary implant to deliver a high dose of radiation in about 3 treatments over 2 days. A single treatment usually takes a few minutes, but men usually have to stay in the hospital until all of the treatments are finished. Iridium-192 and cesium-137 are the radioactive substances most commonly used for HDR brachytherapy for prostate cancer.
HDR brachytherapy is mainly used to treat early stage prostate cancer that is growing quickly and is more likely to spread.
Find out more about brachytherapy.
Systemic radiation therapy
In systemic radiation therapy, a radioactive material (called a radioactive isotope) travels through the body. Cancer cells take up the radioactive material, which kills them.
For prostate cancer, radiation therapy may be given by attaching a radioactive material to a substance that targets specific molecules (such as proteins) on the surface of cancer cells. This allows the radiation to be delivered directly to the cancer cells, which may cause fewer or less severe side effects.
Radium-223 (Xofigo) is the type of systemic radiation therapy used most often for castrate-resistant prostate cancer that has spread to bones and is causing pain. Castrate-resistant prostate cancer means that the cancer came back or didn’t go away after treatment with hormonal therapy.
Side effects can happen with any type of treatment for prostate cancer, but everyone’s experience is different. Some men have many side effects. Other men have few or none at all.
During radiation therapy, the healthcare team protects healthy cells in the treatment area as much as possible. But damage to healthy cells can happen and may cause side effects. If you develop side effects, they can happen any time during, immediately after or a few days or weeks after radiation therapy. Sometimes late side effects develop months or years after radiation therapy. Most side effects go away on their own or can be treated, but some side effects may last a long time or become permanent.
Side effects of radiation therapy will depend mainly on the size of the area being treated, the specific area or organs being treated, the total dose of radiation, the type of radiation therapy and the treatment schedule. Some common side effects of radiation therapy used for prostate cancer are:
- bowel problems, including diarrhea, blood in the stool, rectal pain, rectal burning or rectal leakage
- bladder problems, including more frequent urination, burning with urination or urinary incontinence
- sexual problems, including erectile dysfunction
- pain and swelling between the scrotum and rectum
- blood in the urine, which makes it reddish-brown
Tell your healthcare team if you have these side effects or others you think might be from radiation therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.
Sometimes a man’s PSA level will rise in the first year or 2 after treatment with radiation therapy. This is called a PSA bounce. In most cases, the PSA level will drop again the next time the doctor checks it. Treatment isn’t needed unless the PSA level continues to rise.
Questions to ask about radiation therapy
I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.
Great progress has been made
Some cancers, such as thyroid and testicular, have survival rates of over 90%. Other cancers, such as pancreatic, brain and esophageal, continue to have very low survival rates.