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 hormone therapy together with radiation therapy.

Radiation therapy is given for different reasons. You may have radiation therapy to:

• destroy cancer cells in the body
• treat cancer that is not removed completely with surgery or that comes back after surgery (called salvage radiation therapy)
• relieve pain or control the symptoms of advanced prostate cancer (called palliative therapy)

The following types of radiation therapy are most commonly used to treat prostate cancer.

During external radiation therapy (also called external beam radiation therapy), a machine directs radiation through the skin to the tumour and some of the tissue around it. Doctors give radiation to the smallest area possible to help reduce the risk of side effects. Lymph nodes in the pelvis may also be treated with external radiation therapy.

Doctors may use the following external radiation techniques to accurately target the area to be treated and spare as much surrounding normal tissue as possible.

3D conformal radiation therapy (3D-CRT) has many beams of radiation directed at the tumour. The radiation oncologist uses a CT scan or an MRI to map the exact location and shape of the tumour. The radiation beams are then shaped and aimed at the tumour from different directions to treat the tumour from all angles. Each individual beam is fairly weak and less likely to damage normal tissue. A higher dose of radiation is delivered where the beams meet at the tumour.

Intensity-modulated radiation therapy (IMRT) is similar to 3D-CRT in that it delivers radiation from many different angles to treat the entire tumour. In addition to shaping and aiming the radiation beams, IMRT allows the radiation oncologist to adjust the strength (intensity) of the individual beams. This reduces the dose of radiation reaching nearby normal tissue while allowing a higher dose to be delivered to the tumour. It is useful for treating tumours in hard-to-reach areas.

Volumetric-modulated arc therapy (VMAT) is an advanced form of IMRT that delivers a dose to the entire tumour in a 360-degree rotation. Most modern linear accelerators can deliver this type of treatment. This may shorten the daily treatment time.

Image-guided radiation therapy (IGRT) uses imaging mounted on the linear accelerator to improve the accuracy of radiation therapy. Repeated CT, MRI or PET scans are performed before and during treatment and processed by computers to show changes in tumour size and location compared to the last treatment. This allows the radiation treatment team to adjust your position on the table or the radiation dose to increase accuracy of the treatment. IGRT can lessen the amount of tissue treated and the total dose of radiation received by normal tissue. IGRT may be used to treat tumours in parts of the body that are likely to move, such as the lungs, liver and prostate, or tumours that are very close to vital structures or tissues.

Stereotactic body radiation therapy (SBRT) delivers precisely targeted high doses of radiation to tumours in difficult or hard-to-reach areas in fewer sessions. It is also called stereotactic ablative radiation therapy (SABR). The majority of SBRT is delivered by modern linear accelerators but can also be delivered with a CyberKnife unit. It creates many beams of radiation from different angles that meet at the tumour. The tumour itself receives a high dose of radiation, while the individual beams that travel through surrounding tissue are a low dose. This lowers the effects of radiation on healthy tissue surrounding the tumour. SBRT is given in fewer treatments than standard external radiation therapy.

Proton therapy uses protons (positively charged particles) to treat cancer. It may also be called proton beam therapy. Proton therapy uses proton beams instead of x-ray beams. Protons release more energy after reaching a certain distance and then stop, while x-ray beams release energy before and after they hit their target. So protons cause less damage to tissues they pass through before reaching their target. Proton therapy causes the least amount of damage to nearby normal tissues. A machine called a synchrotron or cyclotron produces the protons. These machines are not available in Canada, and you may have to go to certain centres in the US to receive this treatment.

Brachytherapy is internal radiation therapy. Internal radiation therapy places radioactive materials in the body. Larger doses of radiation can be given with internal radiation therapy than with external radiation therapy. Brachytherapy 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. This type of brachytherapy is called interstitial brachytherapy. 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.

External 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 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 for prostate cancer uses a temporary implant to deliver a high dose of radiation in about 1 to 4 treatments over 2 days. A single treatment usually takes 5 to 15 minutes to deliver the radiation dose, but you may have to stay in the hospital until all of the treatments are finished if multiple treatments are used. 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.

Radioisotope therapy is another type of internal radiation therapy. It may also be called systemic radiation therapy, radiopharmaceutical therapy, radionuclide therapy, or radioligand therapy (RLT). In radioisotope 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 dichloride (Xofigo) is the type of radioisotope therapy used most often for castration-resistant prostate cancer that has spread to bones and is causing pain. Castration-resistant prostate cancer is cancer that has come back or that didn't go away after treatment with hormone therapy.

Lutetium (177Lu) vipivotide tetraxetan (Pluvicto) may be used to treat metastatic castration-resistant prostate cancer that has both of the following qualities:

• It is positive for the prostate-specific membrane antigen (PSMA).
• It has been previously treated with at least one androgen pathway inhibitor and taxane-based chemotherapy.

Lutetium (177Lu) vipivotide tetraxetan may not be available in all parts of Canada or covered by all provincial and territorial health plans.

Side effects can happen with any type of treatment for prostate cancer, but everyone's experience is different. Some people have many side effects. Other people 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:

• fatigue
• 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 the prostate-specific antigen (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.

Find out more about radiation therapy and side effects of radiation therapy. To make the decisions that are right for you, ask your healthcare team questions about radiation therapy.