Radiation Therapy for Prostate Cancer
Radiation therapy is an effective treatment that kills prostate cancer cells by using high energy rays or particles. The radiation can be delivered in several ways, including brachytherapy (using seeds that are implanted in the patient’s body) and external beam radiation that projects the energy through the skin. Radiation therapy for prostate cancer is best delivered by experienced radiation oncologists who work in high volume centers of excellence.
Radiation therapy can:
- Treat both early stage cancers of the prostate gland and more advanced cancers that may have spread beyond the prostate
- Be used alone or with other treatments such as hormone deprivation
- Treat recurrent prostate cancer following surgery
- Treat men with limited spreading (oligometastatic) prostate cancer to reduce the tumor’s size and improve survival and quality of life
- Slow cancer growth, reduce fracture risk
- Be used as a palliative treatment to address pain from advanced cancer
Types of Radiation Therapy to Treat Prostate Cancer
External Beam Radiation Therapy (EBRT)
This is the most common type of radiation therapy, and it is painless. Before treatment, your radiation team will use computerized tomography (CT) scans and magnetic resonance imaging (MRI) scans to map out the location of the prostate and tumor cells.
During each treatment session, X-ray beams are focused on the targeted cancer areas. Oncologists can change the intensity of doses and radiation beams to better deliver high doses of radiation to tumor cells while delivering lower doses to surrounding healthy tissues.
Intensity-Modulated Radiation Therapy (IMRT)
This is a sophisticated form of external beam radiation, which is delivered by linear accelerators (LINACS). Oncologists can change the intensity and shape of the radiation beams to better target radiation delivered to the prostate while limiting radiation to nearby bladder and rectal tissue. Because of the treatment planning involved with this type of radiation therapy, the doctor can deliver far more precise, intense and effective doses of radiation with less risk of damaging surrounding tissue.
Proton Beam Therapy
Proton therapy is an alternative form of EBRT that is being used more frequently now that there are more specially equipped centers that can offer it. The process has evolved from a passive scattering approach to scanning proton beam therapy.
The main benefit of proton therapy is that, because of the beam’s physical properties, the beam stops at the borders of the tumor, preventing an “exit dose” that could affect nearby, healthy tissues in areas outside of the prostate target, such as the bladder and rectum. Current evidence suggests that it is equally effective as other radiation techniques in eliminating prostate cancer.
Stereotactic Body Radiation Therapy (SBRT) or Stereotactic Ablative Radiation Therapy (SABR)
Guided by advanced imaging techniques, SBRT (or SABR) delivers large doses of radiation over a short period of time to a precise area. SBRT is commonly referred to by the names of the machines used to deliver the radiation. SBRT can offer some patients with localized prostate cancer the convenience of fewer treatments while maintaining treatment effectiveness and safety. SBRT may also be used to treat metastases for some patients to reduce tumor mass and potentially enhance survival.
Image-guided Radiation Therapy (IGRT)
IGRT refers to the use of daily imaging to check the tumor target’s position. Most often, this may include a low dose X-ray (kV) or CT scan (cone beam CT). For some patients, gold or platinum fiducial markers may be placed in the prostate before treatment. These markers show up on imaging scans and help the radiation oncologist see the tumor’s position, which helps prepare the patient for treatment each day.
Brachytherapy is also called seed implantation, interstitial radiation therapy or internal radiation therapy. For permanent (low dose rate) brachytherapy, tiny radioactive seeds (about 0.8 millimeters thick and 4.5 millimeters long) are inserted into the prostate using needles that enter the skin just behind the scrotum.
The seeds give off radiation to destroy the cancer cells immediately around them for several months, until the radioactivity has disappeared. The seed enclosure is made of titanium, which is safe to remain in the body. Ultrasound, CT scans and MRI scans can be used to ensure that the seeds are placed in the proper locations.
For some patients, temporary (high dose rate) brachytherapy is used to administer higher doses of radiation through catheters placed in the prostate for a short time. The term “high dose rate” refers to the time over which the radiation is delivered, not the amount of radiation given.
Radium-223, a radioactive substance, is used to treat men with metastatic prostate cancer that no longer responds to hormone therapy. Because it mimics calcium, the radium is selectively absorbed into areas where prostate cancer is invading bone. This revolutionary treatment has been shown to improve the survival of men with metastatic prostate cancer that has spread to the bones, and to delay problems in the bone such as pain or fracture.
Side Effects of Radiation Therapy
Compared to earlier radiation methods, these modern techniques reduce the chance of urinary and bowel problems.
With several treatment options available, your doctor will work with you to develop and oversee a treatment plan that precisely addresses your prostate cancer while minimizing the risk to surrounding tissues.
This is why it is important to choose an experienced radiation oncologist who specializes in the management of prostate cancer. High volume centers where practitioners have significant experience and treat large numbers of patients with prostate cancer may be associated with good outcomes and fewer lasting problems related to treatment. The majority of patients who undergo radiation do not have permanent effects on bowel or urinary function, and patients who develop erectile difficulty after these therapies can often be treated successfully with medications such as sildenafil or tadalafil.