Treating Prostate Cancer with a Missile-Like Delivery of High-Dose Radiation

Pictured: Michael Zelefsky

Radiation oncologist Michael Zelefsky delivers brachytherapy — the placement of radioactive seeds into the prostate gland — with the assistance of an intraoperative CT unit called the O-Arm, which gives real-time snapshots of the prostate.

Memorial Sloan Kettering has long been recognized as a pioneer in the treatment of cancer with radiation. The collaboration of radiation oncologists and medical physicists has produced the development and clinical implementation of new therapies that are “beyond the standard approaches and definitely not out of the textbook,” in the words of Radiation Oncology Department Chair Simon N. Powell.

Evolving technologies and novel enhancements, many of which were developed by Memorial Sloan Kettering medical physicists, have spurred a number of new clinical initiatives led by radiation oncologists investigating more-effective approaches. Memorial Sloan Kettering has particular expertise in the use of intensity-modulated radiation therapy (IMRT), which targets tumors with multiple beams at different angles and intensities.

The SHARP Advantage

Memorial Sloan Kettering’s extensive experience working with IMRT has served as an important foundation for the development of new approaches to treat prostate cancer. With the help of sophisticated image guidance and global positioning system (GPS) techniques, radiation oncologists are now able to offer prostate cancer patients a more focused approach to delivering higher doses of radiation more accurately and in less time than with IMRT.

Using a form of radiosurgery called stereotactic hypofractionated accelerated radiation to the prostate (SHARP), physicians can deliver ultrahigh doses of radiation in only five treatment sessions, compared with close to 50 sessions over ten weeks using the conventional approach.

GPS markers called ferromagnetic transponders are implanted by a urologist into the patient’s prostate gland. The beacons act as homing devices, sending out electromagnetic signals of the prostate’s exact location that can be used to guide the linear accelerator, which delivers high-energy radiation to the prostate over several minutes. If the prostate moves outside of a very tight margin, the radiation treatment can be stopped and adjustments made.

“This kind of missile technology helps us and our medical physics colleagues localize the target with an accuracy akin to the sharpness of a surgeon’s scalpel, sculpt a high dose of radiation around the prostate, and effectively minimize the amount of normal tissue that’s included in that margin,” says radiation oncologist Michael J. Zelefsky. “In this way, we can safely give the entire course of radiation in only five treatment sessions with fewer side effects.”

Memorial Sloan Kettering is the only hospital in Manhattan currently offering this treatment approach and one of only a few academic medical centers in the world doing it within the context of an ongoing clinical trial. Despite the application of high radiation doses, the more than 100 patients with disease confined to the prostate who have been treated with SHARP have tolerated the treatment well. After treatment, patients are closely followed with MRIs and a prostate biopsy.

“SHARP will likely replace the standard way of delivering external radiation therapy for prostate cancer if continued research and patient follow-up show that it is equally or more effective,” says Dr. Zelefsky.

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Improving Brachytherapy with Intraoperative Image Guidance

Over the past 15 years, Memorial Sloan Kettering has established long-term success rates using brachytherapy — the placement of radioactive seeds into the prostate gland to deliver an extraordinarily high dose of radiation to the tumor.

Brachytherapy delivery has been improved by the incorporation of advanced imaging techniques that are commonly used for diagnostic procedures and treatment planning prior to treatment. In fact, it built the only state-of-the-art intraoperative imaging suite in the country dedicated solely to brachytherapy procedures.

One unique feature of the suite is a portable intraoperative CT unit called the O-Arm, which allows physicians to obtain real-time snapshots of the prostate that are fused with ultrasound images to target and confirm the accuracy of radioactive seed placement during the procedure. Memorial Sloan Kettering is currently the only center in the world routinely using this system during brachytherapy.

Marco Zaider, Head of Brachytherapy Physics, and Gikas S. Mageras, Chief of the Computer Service, led a team that developed a unique, patent-pending computer program that enhances the precision of the procedure by enabling physicians to receive instantaneous feedback about exactly where the seeds should be placed within the prostate gland and giving them the opportunity to make corrections on the spot. Being able to obtain and act on this information while a patient is asleep during the procedure in the operating room reduces the possibility that physicians will have to make adjustments later.

“Another advantage is that we can now safely re-treat patients with prostate tumors that have recurred years after treatment with other modalities by using this pinpointed seed implant approach, presenting a treatment option for these patients that didn’t exist before,” says Dr. Zelefsky, who is Chief of the Brachytherapy Service.

Memorial Sloan Kettering’s intraoperative imaging suite also offers MRI, which shows soft tissue differentiation, and PET/CT, which provides detailed anatomical images. Plans are under way to integrate these tools into a computer navigation system that could be used to further refine seed placement during brachytherapy. This unique combination of advanced imaging tools will enhance treatment planning and delivery as well as tumor assessment after treatment, allowing for more-adaptive therapy in which treatment changes can be made based upon tumor response.

“What makes the prostate program at Memorial Sloan Kettering unique is the availability of this comprehensive package of options we can offer our patients,” says Dr. Zelefsky. “Our expertise and this array of options at our disposal enable us to tailor radiation therapy based on the characteristics and location of the tumor, as well as important physical, emotional, and psychological factors that take the entire individual and his quality of life into account.”

This blog entry is part of a larger feature about advances in radiation oncology published in the October 2013 issue of Center News.
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Commenting is disabled for this blog post.

I have recently been diagnosed with prostate cancer. T2a, Gleason 4 +3, PSA 2.8
Ptrvious two yrs 2.0 and 2.2). I am 62 and healthy I work out three times a week and play golf 3-4 times. My parents are 93 and 92 and going strong. Is seed implantation an option for me? What would be my projected life expectancy with this procedure?

Gary, we are unable to answer specific medical questions on our blog. If you would like to make an appointment with a Memorial Sloan-Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to Thanks for your comment.

I had HIFU Surgery 3 1/2 years ago and have recently been diagnosed with prostate cancer once again, either residual or recurring. We are discussing whether to have radiation or robotic surgery as our choice. Can SMART be used with only a tiny piece of the prostate left and how do I choose?

Gary, unfortunately we are unable to answer specific medical questions on our blog. If you would like to make an appointment with a Memorial Sloan-Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to Thanks for your comment.

i completed radiation therapy for prostate cancer on1/31/12,on 1/31/13 psa 0.09
however,on11/13/13 some22 months later psa is 3.1 has the cancer returned?

Dear John, unfortunately, this is not a question we can answer over our blog. If you would like to make an appointment with a Memorial Sloan-Kettering physician, please call our Physician Referral Service at 800-525-2225 during business hours. You can also go to to find out more about making an appointment.

Your work and that of your colleagues at Sloan continue to reassure me as a long-time PCa patient, having undergone 3-D Conformal EBRT there years ago.
Ben Schlossberg

Does Memorial Sloan-Kettering offer radiation therapy for PCa at any locations overseas?

How is SHARP different from Cyberknife?

Dear Bill, we sent your inquiry to Dr. Zelefsky and he responded: “Cyberknife is a name of a company and the machine used to deliver radiation. SHARP delivers this kind of radiation from a high energy linear accelerator. The advantage of our SHARP program is that we routinely track the motion of the prostate during the actual treatment and can adjust the position of the beams even during the treatment as at times the prostate can have small shifts of its position. The Cyberknife system doesn’t routinely do that.” Thank you for your comment.

Does Dr. Zelefsky's current clinical study regarding the use of Viagra to mitigate the side effects of prostate radiation therapy include SHARP patients? (In Fort Wayne we use the term-Cyberknife Photon Beam Therapy.) Also, does he have any preliminary findings available?

Dear Sheldon, we sent your inquiry to Dr. Zelefsky and he responded: “It does not appear that the use of Viagra daily during the radiation treatment would influence or lower the side effects of radiation therapy. Our preliminary results of the study you refer to is a trial where patients were given Viagra on a daily basis to prevent the development of erectile dysfunction. It appears that at this time patients who took the drug on a daily basis had a lowered risk for losing their erections. We anticipate that the full results of this study will be published in the near future.” Thank you for your comment.

Prior to this new treatment called SHARP, did MSK offer a high dose radiation treatment for PCa requiring only 5 sessions, even though it did not use the GPS technology? If so, about how long ago did that start?

Bill, we forwarded your question to Dr. Zelefsky, who said, “We began using the five-treatment hypofractionated short-course regimen at the same time as our using the GPS prostate tracking system. Prior to that we were essentially exclusively using the conventional regimens, which span for ten weeks.” Thank you for your comment.

Is the best after-surgery Radiation treatment 7 days a week for duration of therapy?

Jay, unfortunately we are unable to answer specific medical questions on our blog. If you would like to make an appointment with a Memorial Sloan-Kettering physician, please call our Physician Referral Service at 800-525-2225 or go to Thanks for your comment.

For patients with advanced PCa with metastasis outside the prostate into the spine it has been recommended that a course of IMRT be efficacious to improve the eventual localized urinary disease effects . Might Sharp be a modality in this circumstance ? Thank you

Edward, we are looking into this and will let you know when we have more information. Thank you for your comment.

Dear Edward, we sent your inquiry to Dr. Zelefsky and he responded: “Thank you for your comment and question. Our radiation oncologists generally consider in some cases where the disease spreads to the spine to use stereotactic radiosurgery which is a form of SHARP therapy. The results appear to be more effective than more protracted courses of lower-dose treatments.”

Thank you for reaching out to us.

Thank you Dr Zelefsky for your reply , however , I was questioning the radiation technique to the prostate itself - not the metastatic lesions . Specifically the use of SHARP versus 9 weeks of IMRT - to potentially avoid the localized urinary obstructive symtoms near the later stages of the disease process .Thank You Sir

Dear Edward, SHARP has the advantage of enhanced accuracy and so far patients have tolerated it well. We continue to follow patients to gather longer-term data regarding side effects. We cannot answer personal medical questions on the blog, so if you are interested in a more-personalized assessment to see if SHARP is right for you, we would encourage you to make an appointment for a consultation with one of our specialists by calling our Physician Referral Service at 800-225-2225. Thank you.

My husband was diagnosed at age 60. Gleason 4+3. Had a prostectomy, radiation, tomotherapy, it has been 8 years and now it is in the bones. Had radio surgery in April to the T8 vertebrae. Has been on Lupron since recurrence. PSA went from 60 to 20 after radio surgery, but in September is rose to 35 and now today is 46.9. What would you suggest we do next?

Dear Lori, we are sorry to hear about your husband’s recurrence. We can’t offer personal medical advice on our blog, but if he would like to make an appointment for a consultation with one of our prostate cancer specialists to discuss his treatment options, please call our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

Correction.. Diagnosed at age 50

Might the SHARP therapy be useful against soft tissue residual and recurrent cancer following radiation? In my case the original radiation was in 2011.

Dear Cal, SHARP is a form of stereotactic radiosurgery that may be applied in some people with soft tissue sarcoma. However, we cannot offer personal medical advice on our blog. You may wish to make an appointment with one of our specialists for a consultation and discussion about whether this is a treatment option for you. If so, please call our Physician Referral Service at 800-525-2225. Thank you for reaching out to us.

My son has the BRCA 2 gene. How often should he have his PSA checked.

Eileen, thank you for reaching out. We consulted with MSK’s James Eastham, who recommends that for someone with BRCA2:

He should get a baseline PSA at age 40-45 years, and based on that value the frequency of PSA testing will be determined. If the PSA is less than 1, it can be repeated in 3-5 years; if PSA between 1 and 3 get a repeat in a year or two; if PSA greater than 3 he should be evaluated.

Is a 55 year old man with recently diagnosed prostate cancer whose PSA is 4.2 and with 3/10 positive biopsy cores of 80%, 60% and 50% a good candidate for SBRT? One of the cores reveals perineural invasion. Without knowing for sure the cancer is localized to the prostate how can the radiation be certain to target all the cancer?

Can prostate cancer recur in a patient who has undergone a davinci prostatectomy?

Dear Cee, there is a chance of a man having a recurrence after prostatectomy, whether or not it has been performed with robotic assistance. The surgeon’s experience with this technology plays a role, as does the aggressiveness of the patient’s disease, lymph node involvement, and many other factors. It’s important for patients to be monitored over time for signs of recurrence - how often a person needs follow up exams is determined by his physician. If you or a loved one has questions or concerns about cancer recurrence, please circle back with the surgeon who performed the operation. Thank you for reaching out to us.

having done [email protected], oligometastatic, psa after one year 0.05, do i need any extra treatment to stay in remission. thanks

Dear Munish, we sent your question to MSK radiation oncologist Dr. Michael Zelefsky and he responded:

“In general, after SBRT, if the full dose was given, patients are followed and no additional therapies are required unless there is evidence of the disease recurring.”

We recommend that you follow up with your physician for more specific information regarding your particular circumstances and appropriate next steps in your care.

Thank you for reaching out to us.

I have been on testosterone replacement therapy for 18 years. Recently I had an MRI with a PIRAD Score of 4/5. I am waiting on biopsy results and doing my research. Since, PSA does not initially drop to its nadir after radiation treatment and since testosterone replacement therapy can perhaps raise PSA levels and assuming that I am able to continue with TRT after treatment it seems to me that surgery is a better option for one who plans to continue with TRT since the PSA drops to near zero thereby resulting in a post treatment follow-up will be less "muddied" by the TRT. Is this logical?

do you use hormone therapy combined with radiation therapy for any prostate cancer treatments? Also is hormone treatment effective/safe?

What would you recommend for me? I am at the 2 year mark since my RP with 12 Lymph Nodes on each side removed and my left nerve spared. 3 of 12 with gleason 4+5=9. All margins negative, negative on CT/Bone/MRI and no lymph nodes or seminal vessile invasion.

PSA history:
ID Date PSA Score Location of Test Comments
1 10/12/2016 <0.015 Dr. Porters Office Lab Corp
5 2/15/2017 <0.015 Dr. Porters Office Lab Corp
2 2/2/2018 0.009 Dr. Porters Office Lab Corp
3 4/16/2018 0.008 Dr. Porters Office Lab Corp
4 8/9/2018 0.014 Dr. Porters Office Lab Corp

I live in Seattle Washington.
Kind Regards,

Dear Brian, we are not able to provide personal medical advice on our blog. If you would like to arrange a consultation to discuss these findings with a doctor at MSK, you can call 800-525-2225 or go to for more information. Otherwise, this is something you should discuss with your healthcare team. Thank you for your comment, and best wishes to you.

I had sharp about 2 years ago. Do I have to have a biopsy if my PSA is low. Are there any other tests instead of a biopsy