Radiation Therapy for Prostate Cancer

External Beam (EBRT)

Beams of radiation are focused on the prostate gland. It is delivered from a machine outside the body. This type can be used to try to cure early stage cancer. It may also help to ease problems such as bone pain if the cancer has spread. Measurements will be taken before treatment. This is done in an appointment called simulation. It may include CT or MRI scans. They will help to find the best angle and dose of radiation. A plastic mold of your body may also be made. It will help to keep you in the same position for each treatment. This will make the radiation aim more accurate. EBRT is often given 5 days a week for several weeks. Each treatment is like getting an x-ray with stronger radiation. The procedure is painless. Each treatment lasts only a few minutes. Setup time before treatment takes longer.

Types of EBRT include:

• 3D conformal radiation therapy (3D-CRT)—uses special computers to map the prostate. Radiation beams are then shaped and aimed at the prostate from several directions. This makes it less likely to damage normal tissue.
• Intensity modulated radiation therapy (IMRT)—an advanced form of 3D therapy. This is the most common type of EBRT for prostate cancer. The machine moves around the patient as it delivers radiation. The beam is shaped, aimed as above. The strength of beam can also be changed. It will limit radiation of healthy tissue and increase radiation to cancer. IMRT is able to give large doses of radiation in each session. The treatment is given over just a few days.
• Stereotactic body radiation therapy (SBRT)—is often known by the names of the machines that deliver the radiation, such as Gamma Knife®, X-Knife®, CyberKnife®, and Clinac®. The main advantage of SBRT over IMRT is that the treatment takes less time (days instead of weeks). The side effects, though, are not better. In fact, some research has shown that some side effects might actually be worse with SBRT than with IMRT.
• Proton beam radiation therapy—focuses beams of protons instead of x-rays on the cancer. Protons cause little damage to tissues they pass through. They also release their energy after traveling a certain distance. This means that proton beam radiation can deliver more radiation to the prostate. It will also cause less damage to nearby normal tissue. Proton beam radiation can be aimed with techniques similar to 3D-CRT and IMRT. **Proton beam therapy might be more effective than using x-rays. So far studies have not shown if this is true. Right now, proton beam therapy is not widely available. The machines needed to make protons are very expensive. They aren’t available in many centers in the United States. Proton beam radiation might not be covered by all insurance companies at this time.

Brachytherapy

Seeds, the size of a grain of rice, are implanted inside the body. They're placed in the prostate between the scrotum and anus. Higher doses of radiation can be used with this method. The seeds can be:

• Permanent—Low-dose seeds are placed. They emit radiation. They can be used for a longer time. In some, it may be months.
• Temporary—A high-dose seed is sent into the body via tubes. Radiation is given for up to 15 minutes, then it's taken out. This may be given up to 3 times over the course of 2 days. The tubes stay in place until you no longer need to be treated.

In some cases, you may need more than one type of brachytherapy.

Radiopharmaceutical Therapy

Alpha emitter radiation therapy is delivered to the cancer through an IV. It’s used to kill cancer that’s spread to the bones.

Side Effects and Management

Radiation aimed at the pelvis causes irritation. You may have:

• Erectile dysfunction
• Blood in the stool
• Pain during bowel movements
• Diarrhea
• A harder time holding urine
• To pass urine more often
• Narrowing of the tube that carries urine out of the body from the bladder—rare

There are many ways to treat these problems. Other common issues are dry, sore skin, nausea, vomiting, and feeling tired because of anemia. Talk to your healthcare team as soon as these symptoms appear so they can be better controlled. In some cases, the dose of radiation may be changed.