What is Radiation Therapy?
Radiation therapy uses high-energy rays to kill or slow the growth of cancer cells. Radiation can be used as the primary treatment for prostate cancer (in place of surgery). It can also be used after surgery if the cancer is not fully removed or if it returns.
Radiation therapy mostly involves photon beams or proton beams. Photon beams make up traditional x-rays. They carry a very low radiation charge and mass, and can scatter to nearby health tissue. On the other hand, proton beams have more charge and heavy mass and can target deep tissue. A physician can direct proton radiation treatment to the specific site of cancer, minimizing damage to nearby healthy tissue.
Before you begin, it helps to ask your doctor(s) why they recommend one type of radiation therapy over another.
There are two primary kinds of radiation therapy used for prostate cancer:
• External beam radiation therapy
• Brachytherapy (internal radiation)
External Beam Radiotherapy
Traditionally, External beam radiation therapy (EBRT) has used the photon (x-ray). Photon-based external-beam x-rays may damage nearby healthy tissue. That damage can cause side effects. Your healthcare provider may be able to offer three-dimensional conformal radiotherapy (3DCRT) or intensity-modulated radiotherapy (IMRT) instead. Some newer 3DCTR machines have imaging scanners built into them. 3DCRT creates 3D digital data to map the shape, size and location of tumors. It allows higher doses of radiation to be delivered to cancer cells while protecting surrounding healthy tissue.
Proton Beam Therapy (PBT) is another type of EBRT, but it uses the proton. It uses a machine called a synchrotron or cyclotron to speed up and control the protons. High-energy protons can travel deeper into body tissue than low-energy photons. With proton therapy, radiation does not go beyond the tumor, so nearby tissue is not affected. There are fewer side effects. Intensity-modulated proton beam therapy (IMPT) is a new way to deliver targeted PBT, but these machines are expensive and are not offered everywhere.
Stereotactic Body Radiation Therapy (SBRT) delivers large doses of radiation to exact areas, such as the prostate, with advanced imaging. The entire course of treatment is given over a shorter period, for just a few days. SBRT is often known by the names of machines that deliver the radiation, such as Gamma Knife®, X-Knife®, CyberKnife® and Clinac®.
With any radiation treatment, the side effects should be discussed with you before you begin.
Prostate Brachytherapy (Internal Radiation Therapy)
With brachytherapy, radioactive material is placed directly into the prostate using a hollow needle. There are two types of brachytherapy: low dose rate (LDR) brachytherapy and high dose rate (HDR) brachytherapy.
LDR brachytherapy - is when your doctor uses a thin needle to insert radioactive "seeds" (the size of a rice grain) into the prostate. These seeds send out radiation, killing the prostate cancer cells nearby. In LDR, the seeds are left in the prostate even after treatment is finished.
HDR brachytherapy - is when your doctor puts radiation into your prostate using a slightly larger hollow needle to insert a thin catheter. This catheter stays in your body until treatment is done. The radiation source stays in your prostate for a short period of time. Once your treatment is done, all radioactive material is removed.
Anesthesia is needed to insert the needles for both LDR and HDR brachytherapy. You may need to stay in the hospital overnight.
Sometimes radiation therapy is combined with hormone therapy to shrink the prostate before starting. Or, hormone therapy may be combined with external beam therapy to treat high-risk cancers.
What are the Benefits, Risks and Side Effects of Radiation Therapy?
The benefit of radiation therapy is that it is less invasive than surgery. Whether the radiation is given externally or internally, this treatment is effective for early stage prostate cancer. Some need both types of radiation combined to treat their cancer.
The main side effects of radiotherapy are incontinence and bowel problems. Urinary problems usually improve over time, but in some men they never go away. Erectile dysfunction, including impotence, is also possible. Many men feel tired for a few weeks to months after treatment.
If hormone therapy is used with radiation, sexual side effects are common. These can include loss of sex drive, hot flashes, weight gain, fatigue, decreased bone density and depression. Fortunately, these side effects can be managed and usually go away when hormone therapy is stopped.
It helps to work with your radiologist before you begin treatment to prepare for any known side effects in advance. Follow-up visits with your healthcare team will help you address any new problems.
Updated August 2018