Radiation Therapy for Prostate Cancer

Radiation therapy for prostate cancer involves the use of high-energy beams or radioactive seeds to eliminate tumors. The most common types we recommend for prostate cancer include brachytherapy, image-guided radiation therapy (IMRT), stereotactic radiosurgery, and proton therapy. 

Which radiation therapy approach we recommend depends on the unique characteristics of your disease. We offer radiation therapy, either alone or in combination with hormone therapy, to combat all stages of prostate cancer. In some cases, we use it as a primary treatment approach; in others, we use it after surgery if there are signs that your cancer has come back.

Our radiation oncologists are continually working to advance the field. As part of this effort, we offer some patients access to clinical trials of new approaches to radiation therapy. By participating in a clinical trial, you may have access to techniques or combinations of therapies that are not yet widely available.

Why Choose MSK

  • 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 stereotactic radiosurgery.

Types of Radiation Therapy Used to Treat Prostate Cancer

Our doctors will work with you and the other members of your treatment team to help you decide which approach, or combination of approaches, is best for you.

Whether you have an early-stage tumor or more advanced prostate cancer, the options we typically recommend include:

  • internal forms of radiation therapy (called brachytherapy), such as radioactive seed implantation. These procedures are performed as outpatient treatments under anesthesia. Most patients go home the same day as the procedure without a catheter in the bladder. MSK doctors pioneered this form of treatment.
  • external approaches, including image-guided radiation therapy and stereotactic radiosurgery

External approaches, called external-beam radiation therapy (EBRT), involve aiming radiation directly at your prostate from outside your body using a device called a linear accelerator. We use this approach by itself to treat localized tumors, or we combine it with brachytherapy or other therapies to treat more aggressive disease.

At Memorial Sloan Kettering, we use three primary types of EBRT to treat prostate cancer: image-guided, intensity-modulated radiation therapystereotactic radiosurgery; and proton therapy.

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

With image-guided, intensity-modulated radiation therapy (IG-IMRT), we use real-time imaging to mold radiation beams to the contours of your tumor. Because the normal movements of your body can cause the prostate to move slightly during or between treatments, we place several small markers in the prostate before beginning the radiation session. Having these markers placed is very similar to having a prostate biopsy. Called fiducial markers, they’re made of gold and allow a CT scanner that is part of the linear accelerator to locate the current location of the tumor and the prostate gland with sub-millimeter accuracy.

We also use a type of marker called a beacon transponder (the Calypso® system) to send signals to a specially designed tracking system. Similar to a GPS, the beacon transponder allows your radiation therapists to precisely check the position of your tumor during each treatment. This helps us to make any necessary adjustments and ensures that the radiation poses the least risk to healthy tissues while maximizing the dose to the tumor.

When used alone, IG-IMRT is given over a period of nine weeks (approximately 48 treatment sessions). When combined with radioactive seed implantation, we may give IG-IMRT over a period of five weeks (25 sessions). IG-IMRT is offered more commonly in men who have significant urinary problems before treatment begins.

Stereotactic Radiosurgery

MSK’s radiation oncology team is also advancing the use of an extremely precise, ultra-high-dose form of radiation therapy known as stereotactic radiosurgery (also called stereotactic body radiation therapy, or SBRT). It uses innovative imaging technologies combined with a sophisticated computer system (similar to the CyberKnife® system) to deliver very high doses of radiation to tumors with an accuracy of under a millimeter. While the CyberKnife system requires a long period of time on the treatment table (close to one hour), our stereotactic approaches can effectively deliver the treatment in 3 to 4 minutes.

Treatment using stereotactic radiosurgery can be completed in five sessions. It has been effective for many of our patients and has similar or fewer side effects than more conventional external radiation techniques. We have already treated hundreds of patients with this approach, and we have found that these treatments have been well tolerated, and many have had excellent results several years later. These treatments are convenient for patients because the entire course is completed in a little over a week.

For men with more aggressive disease, we may combine stereotactic radiosurgery with brachytherapy seed implants. We tend to use stereotactic radiosurgery in men with relatively good urinary function.

Proton Therapy

Some men with prostate cancer may elect to receive proton therapy. Proton therapy is a form of external-beam radiation therapy. Proton therapy may be another way to deliver a high radiation dose to the prostate while lowering the radiation dose to normal surrounding tissue. It is unclear if there is any advantage to proton therapy compared with IG-IMRT. We are now studying how these approaches compare in terms of side effects and outcomes.

Which Type of Radiation Therapy Is Right for You?

It can be confusing to know which radiation treatment approach is your best choice. We’re here to help. When recommending one approach or another, our team of radiation oncologists will consider a number of factors, including the aggressiveness of your tumor, how advanced your disease is, and your own preferences.

It can be helpful to know about different radiation treatment scenarios that occur based on the types of conditions we commonly see. Here are a few.

Radiation Therapy for Localized Prostate Cancer

Localized prostate cancer refers to a tumor that is clearly confined within the prostate. Radiation therapy options for men with early-stage, localized prostate cancer include:

  • low-dose-rate (LDR) brachytherapy
  • stereotactic radiosurgery

For men with locally advanced prostate cancer — which means the cancer has spread outside the prostate to nearby tissues — options may include:

  • LDR brachytherapy combined with a short course of daily IG-IMRT
  • IG-IMRT combined with hormone therapy
  • High-dose-rate (HDR) brachytherapy combined with a short course of daily IG-IMRT

Together with your radiation oncologist, we can help you figure out which of these approaches is best for you.

Often, when a tumor is more advanced or aggressive, men receive hormone therapy before radiation therapy begins and continue it throughout the course of their treatment. Some receive hormone therapy after radiation therapy finishes as well. Hormone therapy reduces the level of testosterone throughout the body (testosterone stimulates the growth of prostate cancer cells).

Radiation Therapy after Prostatectomy

Many men undergo radical prostatectomy (surgery to remove the prostate gland) as a primary treatment for prostate cancer. However, sometimes there will be indications several years after surgery that the cancer has returned. If you experience one or more of these signs that the cancer is back, such as a rising level of prostate-specific antigen (PSA) or evidence on a scan, radiation therapy can eliminate or control it.

We may also recommend radiation therapy if the tumor has not been completely removed by surgery, or if at the time of surgery the tumor was found to extend outside the prostate gland. Even if your PSA level is zero, radiation therapy can be important to eliminate cancer cells that may have escaped the prostate.

We commonly use IG-IMRT following surgery. If a rising PSA level or a scan indicates that prostate cancer has recurred locally and has spread to nearby tissues, IG-IMRT can be combined with hormone therapy, which reduces the level of testosterone throughout the body (testosterone stimulates the growth of prostate cancer cells).

Radiation Therapy for Bone Metastases

Because radiation therapy is so focused, it’s not often used to treat cancer that has spread from the prostate to other parts of the body. However, we’ve developed and have extensive experience using stereotactic radiosurgery as a treatment for certain prostate cancers that have spread to the bones, where they can cause considerable pain. It can eliminate bone metastases with great precision and may dramatically improve your quality of life if you have advanced prostate cancer.

Managing Side Effects of Radiation Therapy

Advances in the precision of radiation therapy have lessened the risk of complications. And our doctors are constantly developing new ways to minimize side effects. For example, we are one of the few hospitals in the United States using an FDA-approved biodegradable gel inserted before treatment to protect the rectum. 

Still, radiation can cause short- and long-term side effects, including incontinence (the loss of bladder control), erectile dysfunction, bowel problems, fatigue, and symptoms in other parts of the body (if you receive radiation therapy for disease that has spread outside the prostate).

Any side effects you experience depend on which part of the body receives radiation. In the case of such techniques as image-guided radiation therapy and stereotactic radiosurgery, it also depends on which normal structures are in the path of the radiation’s beam. In addition, radiation therapy is sometimes delivered in combination with hormonal therapy, which can cause impotence. Our experts will work closely with you and your medical team to manage any treatment-related difficulties you may experience, such as bladder, bowel, or erectile dysfunction. However, because of the sophisticated targeting systems we use, severe long-term bladder and bowel problems are now rare.

Bowel and Bladder Problems

During the course of radiation treatments, some men experience diarrhea or frequent and uncomfortable urination. Please tell your treatment team if you have any of these problems. We can recommend medications and other methods that can help alleviate these uncomfortable side effects.

Erectile Dysfunction

Radiation therapy, whether external or internal, can cause erectile dysfunction in some men. Our team of doctors, nurse practitioners, and psychologists who specialize in sexual medicine can help you manage these side effects. We are studying treatments for men who experience the sexual side effects of prostate cancer treatment and will collaborate with your care team to minimize the impact of radiation therapy on your sexual health.


Everyone responds differently to radiation treatment. Some patients feel little effect; others may become fatigued as treatment progresses. Getting enough rest is important. After treatment ends, almost all patients return to their previous energy levels. However, you should certainly report any unusual fatigue to your treatment team.

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.