Radiation Therapy for Prostate Cancer

Radiation Therapy for Prostate Cancer

Memorial Sloan Kettering radiation oncologist Christopher Crane with a patient

Radiation oncologist Christopher Crane, pictured in Memorial Sloan Kettering's Linear Accelerator Treatment Suite.

Radiation therapy uses high-energy beams or radioactive seeds to kill tumors. The most common types we use for prostate cancer are:

Everyone’s prostate cancer is different. The radiation therapy that’s best for you depends on the type of cancer you have. We use radiation therapy alone, or with hormone therapy. In some cases, radiation therapy is the primary treatment and is a better option than surgery. In other cases, we use radiation therapy after surgery.

Our radiation oncologists (cancer doctors) are always working to improve outcomes after treatment. MSK patients may be able to join our research studies, known as clinical trials, that test new radiation therapy treatments. When you join a clinical trial, you may have access to new methods not yet widely available.

Why Choose MSK
  • We are ranked #1 in the nation for Urology Cancer Care by U.S. News & World Report.
  • We have a large team of medical physicists developing, refining, and fine-tuning your personalized treatment plan to ensure it is as precise as possible.
  • The doctors, nurses, and therapists caring for you all specialize in prostate cancer.
  • Our imaging techniques ensure we deliver the safest, most targeted treatment possible.
  • We have the most experience in all forms of radiation therapy for prostate cancer. In fact, we pioneered the field of brachytherapy.
  • We offer a faster and more-effective alternative to CyberKnife called MSK PreciseTM

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Types of Radiation Therapy to Treat Prostate Cancer

Our doctors will work with the rest of your care team to help you choose treatments best for you. Radiation therapy is used for most cancer stages, from early-stage tumors to more advanced prostate cancer. There are 2 kinds of radiation therapy, internal and external:

  • Internal radiation therapy is when we implant something inside your body, such as radioactive seeds.
  • External radiation therapy takes place outside your body. This kind of therapy uses high-energy rays to damage cancer cells so it’s hard for them to grow.

An example of internal radiation therapy is brachytherapy (BRAY-kee-THAYR-uh-pee). These procedures are outpatient treatments done under anesthesia, so you’ll be asleep. You can go home the same day. MSK doctors were among the first to offer this form of treatment.

External beam radiation therapy (EBRT) uses a treatment machine called a linear accelerator. It aims a beam of radiation directly to the prostate. The beam passes through your body and destroys cancer cells in its path. You won’t see or feel the radiation. MSK uses EBRT to treat localized tumors. These are tumors that are only inside the prostate. If the prostate cancer has spread, we combine EBRT with brachytherapy or other therapies.

MSK uses 3 kinds of EBRT to treat prostate cancer:

Image-Guided, Intensity-Modulated Radiation Therapy (IG-IMRT)

Image-guided, intensity-modulated radiation therapy (IG-IMRT) uses images that are taken in real time to mold radiation beams to your tumor. The normal movements of your body can cause the prostate to move slightly during or between treatments. We put several small gold markers (fiducials) in the prostate before we start the radiation session. They give the tumor’s exact location and let your doctors track your prostate before and during your treatments. The procedure to place these markers is very similar to having a prostate biopsy.

If you have your whole prostate, you will have IG-IMRT in about 26 treatment sessions over 5 weeks. If you also have brachytherapy, you will have IG-IMRT in 25 sessions over 5 weeks. We usually offer IG-IMRT to people who had significant urinary problems before their treatment started.

MSK Precise™

MSK PreciseTM is a type of radiation therapy. It’s also known as hypofractionated radiation therapy or stereotactic radiotherapy. Since 2009, MSK Precise has been the most common external radiation treatment MSK uses for prostate cancer.

You may have heard about CyberKnife treatments for prostate cancer. CyberKnife is just a brand name for a stereotactic body radiation therapy device. MSK Precise uses similar technology.

MSK Precise destroys tumors with very intense doses of radiation in fewer sessions than standard radiation therapy. Treatment doses are stronger compared with other radiation therapies, such as IG-IMRT or proton therapy. There are only 5 treatment sessions, each lasting only about 3 to 4 minutes. You can complete the entire course in a little over a week.

MSK Precise uses an advanced computer system to deliver high doses of radiation to prostate tumors. It also uses magnetic resonance imaging (MRI) to help map out treatments. These pictures help doctors see the tumor and normal tissues more clearly. They can precisely target the therapy and keep the radiation to within 1 millimeter of the tumor.

This precise, high-dose radiation is what makes MSK Precise different from traditional radiation therapy. The accuracy means the radiation is less harmful to nearby healthy tissue. It offers the potential that you will have fewer side effects. This therapy has very low rates of incontinence (urinary leakage) and problems with the rectum (the bottom section of your colon). As is the case with other external radiation therapies, it has few sexual health side effects.

We often use a rectal spacer, a special type of protection for your rectum. MSK has more experience with using this special protection than any hospital in the world. We place the SpaceOAR® hydrogel rectal spacer between your prostate and rectum to move them apart. This protects you from radiation and reduces some side effects of radiation therapy. The rectal spacer will stay in place for about 3 to 6 months. Then it will be absorbed by your body and come out in your urine.

MSK Precise usually is best for people who have fairly good urinary function. If you have more aggressive prostate cancer, we may recommend internal radiation therapy such as high dose rate (HDR) brachytherapy. With HDR brachytherapy, we temporarily place radioactive source in the prostate. You then will have an MSK Precise treatment 1 to several weeks later.

Proton Therapy

Proton therapy is a type of external beam radiation therapy. It is a way to deliver a high radiation dose to the prostate and lower radiation to healthy nearby tissue. It is unclear if there is any advantage to proton therapy compared with IG-IMRT. MSK is studying how side effects and outcomes for these 2 treatments compare.


How Do I Choose Which Radiation Therapy Is Right for Me?

Deciding which radiation treatment is best for you can be confusing. We’re here to help. Before we make a recommendation, our team of radiation oncologists will evaluate your situation. They will look at how aggressive and advanced the prostate cancer is. They will ask you about your quality-of-life choices. Here is information about the treatments we usually recommend for 3 common prostate cancer conditions.

Radiation Therapy for Localized Prostate Cancer

Localized prostate cancer means it has not spread outside the prostate. Radiation therapy for early-stage, localized prostate cancer includes:

Your radiation treatments will depend on the type of prostate cancer you have. Your radiation oncologist can help you decide which radiation treatments are best for you.

When the disease has spread outside the prostate gland, there are 2 common treatment options.:

  • IG-IMRT combined with hormone therapy. Treatments last about 5 weeks.
  • High-dose-rate (HDR) brachytherapy combined with a short course of daily IG-IMRT with or without hormone therapy. Treatments may be as few as 5 or as many as 25.

With advanced or aggressive cancer, there’s risk of the tumor spreading into areas outside the prostate. In such cases, we may combine radiation therapy with hormone therapy.

Hormone therapy slows or blocks the growth of prostate cancer cells. Testosterone is a male sex hormone that can cause prostate cancer cells to grow. Hormone therapy lowers the amount of testosterone your testicles make.

We start your hormone therapy before you have radiation therapy. This is because radiation therapy works better when hormone therapy continues throughout treatment. Sometimes hormone therapy also is given after radiation therapy treatment is over. Our doctors will talk with you about whether hormone therapy is right for you.

Radiation Therapy after Prostatectomy

A radical prostatectomy is surgery to remove the prostate gland. It’s a primary treatment for prostate cancer. After surgery, there sometimes are signs the cancer has returned. These signs can include a rising level of prostate-specific antigen (PSA) or an abnormal scan. If you’ve already had a radical prostatectomy, we may recommend radiation therapy. Very precise doses of radiation may be able to kill or control the cancer.

We sometimes recommend radiation therapy after surgery when the cancer is gone, but there is a high risk it will return. Your doctors will talk with you about whether this treatment is right for you.

After surgery, we often use IG-IMRT treatments over a period of about 7 weeks. IG-IMRT can be combined with hormone therapy if it looks like cancer has come back in the prostate area. A rising PSA level or a scan will help diagnose if the cancer has returned.

Radiation Therapy for Metastatic Prostate Cancer

Metastatic prostate cancer is cancer that has spread to other parts of the body. We have treatments for prostate cancer that already metastasized (spread) at the time you are diagnosed. If it spread to a few spots in your bones, we recommend 26 treatments of IG-IMRT to the prostate. We also may add a short course of 1 to 5 treatments of radiation to the tumors in the bone. Research studies, known as clinical trials, show this treatment may help you live longer.

After your surgery, imaging may show the prostate cancer has spread to a few areas in the bone. We may recommend a short course of 1 to 5 treatments of radiation therapy to those spots, along with hormone therapy.

Managing Side Effects of Radiation Therapy

Radiation therapy at MSK is very precise, so there is less risk of complications. MSK doctors are working on new ways to accurately target a tumor so there are even fewer side effects. MSK was one of the first cancer centers to use an MR linear accelerator to treat people with prostate cancer. This machine lets doctors use magnetic resonance imaging to deliver radiation therapy.

However, radiation can cause short-term side effects and long-term side effects. Side effects depend on the area that was treated and whether organs were in the path of the radiation’s beam.

Bowel and Bladder Problems

Radiation causes inflammation (swelling) in tissue that was touched by the radiation beam. This swelling can affect activity in your bowel and your bladder. Your bowel is your small and large intestines. Your bladder stores urine until you need to urinate.

You may:

  • Need to urinate more often than usual.
  • Need to urinate at night more often than usual.
  • Have sudden urges to urinate.
  • Have loose stool (poop).
  • Have mucous discharge from your anus (the opening of your rectum where stool leaves your body).
  • Have diarrhea (loose or watery stool) more often.

During your treatment, your care team will monitor you closely to help with any side effects. We may recommend you change your diet or offer you medication that can help. Please tell your care team if you have any side effects, so they can help you. Severe long-term bladder and bowel problems are very rare.

Erectile Dysfunction

Like other treatments for prostate cancer, radiation therapy sometimes causes erectile dysfunction (ED). This is when it is not easy or not possible to get or keep an erection (getting hard). MSK has a team of doctors, nurse practitioners, and psychologists who are experts in sexual medicine. They can help you manage these side effects. We are studying ways to help with the sexual side effects of prostate cancer treatment. MSK’s sexual medicine experts will work with your care team to limit any sexual health side effects.


Some people get fatigue during treatment. Fatigue is a feeling of being very tired or weak. Healthy eating, light exercise, and getting enough rest are important. They help you feel less fatigue before, during, and after treatment. Most people recover fully after treatment. You can continue the activities you enjoyed.

Selected Publications

Zelefsky MJ, Poon BY, Eastham J, et al. Longitudinal assessment of quality of life after surgery, conformal brachytherapy, and intensity-modulated radiation therapy for prostate cancer. Radiother Oncol. 2016 Jan 9. pii: S0167-8140(15)00668-4.

Kohutek ZA, Weg ES, Pei X, et al. Long-term Impact of Androgen-deprivation Therapy on Cardiovascular Morbidity After Radiotherapy for Clinically Localized Prostate Cancer. Urology. 2016 Jan;87:146-52.

Hathout L, Folkert MR, Kollmeier MA, et al. Dose to the bladder neck is the most important predictor for acute and late toxicity after low-dose-rate prostate brachytherapy: implications for establishing new dose constraints for treatment planning. Int J Radiat Oncol Biol Phys. 2014 Oct 1;90(2):312-9.

Zelefsky MJ, Shasha D, Branco RD, et al. Prophylactic sildenafil citrate improves select aspects of sexual function in men treated with radiotherapy for prostate cancer. J Urol. 2014 Sep;192(3):868-74.

Spratt DE, Zumsteg ZS, Ghadjar P, et al. Comparison of high-dose (86.4 Gy) IMRT vs combined brachytherapy plus IMRT for intermediate-risk prostate cancer. BJU Int. 2014 Sep;114(3):360-7.

Polkinghorn WR, Zelefsky MJ. Improving outcomes in high-risk prostate cancer with radiotherapy. Rep Pract Oncol Radiother. 2013 Nov 11;18(6):333-7.

Kollmeier MA, Fidaleo A, Pei X, et al. Favourable long-term outcomes with brachytherapy-based regimens in men ≤60 years with clinically localized prostate cancer. BJU Int. 2013 Jun;111(8):1231-6.

Zumsteg ZS, Spratt DE, Pei I, et al. A new risk classification system for therapeutic decision making with intermediate-risk prostate cancer patients undergoing dose-escalated external-beam radiation therapy. Eur Urol. 2013 Dec;64(6):895-902.