Advances in external beam radiotherapy for treatment of localized prostate cancer

In the past year or so there have been three significant technological advances in the use of external beam radiotherapy for the treatment of localized prostate cancer, and we want to be sure that the patient community is both aware of and understands the limitations of these technological advances.

The Potential of CyberKnife Radiotherapy

The first is the relatively widely publicized application of Accuray’s CyberKnife technology in the treatment of prostate cancer. The application of this technology was first raised and discussed on The “New” Prostate Cancer InfoLink back in July 2008, and we would particularly refer patients to the comments following that initial commentary. In particular, we feel that the comments made by Dr. Don Fuller of CyberKnife Centers of San Siego were helpful, staightforward, and informative.

The “New” Prostate Cancer InfoLink still believes that we need long-term data (at at least 5 years of follow up) to fully support the argument that CyberKnife therapy for localized prostate cancer is as effective and as safe as “conventional” intensity-modulated external beam radiation therapy (IMRT), but it is clear that such data are being collected. We would encourage any patient who decides to be treated with CyberKnife therapy to do so within the context of a clinical trial (three such trials are currently listed on

The other issue that patients need to be aware of is that insurance coverage of CyberKnife radiation therapy for prostate cancer is variable. Even Medicare does not have national coverage for this technique, so you need to be sure that your insurer will cover this form of treatment.

What is the single most important benefit of CyberKnife therapy for the patient? The fact that treatment can be carried out in just five clinic visits compared to the 40 or so visits over 8 weeks required for conventional IMRT.

What About RapidArc Radiotherapy?

The RapidArc technology from Varian Oncology is a form of intensity-modulated radiation therapy (IMRT) that has been developed by Varian Oncology to offer a similar five-visit form of external beam radiation treatment to that offered using the CyberKnife. It is very clear that the idea of radiation treatment that can be delivered effectively and safely within short timeframes will be attractive to any patient (just as laparoscopic surgery is more attractive than “open” radical prostatectomy, which leaves a 6-inch abdominal scar). Again, the “New” Prostate Cancer InfoLink first reported on the clinical use of this system in July 2008.

As with the CyberKnife technology, the accumulated data on treatment of patients with RapidArc technology is limited. So we really don’t know yet whether this form of technology is as effective and safe as traditional IMRT. To date we are aware of only one clinical trial of RapidArc technology in the treatment of prostate cancer, and that trial is being conducted in British Columbia in Canada. We would have liked to see some sort of registry trial put in place by Varian Oncology to track outcomes of all prostate cancer patients being treated with the RapidArc system so as to accumulate truly helpful outcomes data over time, but probably that was too much to hope for!

Calypso Four-Dimensional Organ Location

A very different form of technology, the Calypso® 4D Localization System™ from Calypso Medical is a system that can be used to track and allow for small movements of the prostate in real time during external beam radiotherapy.

The ability to ensure that radiation therapy is delivered with absolute precision to a specific organ is fundamental to quality of outcome following radiotherapy for any disorder. But some organs may be positioned slightly differently in the body from day to day and even may move slightly during radiotherapy. The prostate is one of those organs.

Calypso Medical discovered that tumor motion during patient radiation therapy was a daily challenge for radiation clinicians. They therefore set out to develop and deliver a technological solution to the problem — a system that could continuously monitor the location of a tumor throughout the duration of radiation treatment and adjust delivery of the radiation accordingly. Their goal was a technology that had to be efficient and easy to use for the clinician, and that could help to direct radiotherapy in real time with sub-millimeter accuracy.

The Calypso® 4D Localization System™, also sometimes referred to as GPS for the Body®, was first approved by the Food and Drug Administration (FDA) in July 2006. However, it has only really started to become widely available and used in the past 12 months or so. Many leading cancer institutions in the United States have adopted this new unique technology for prostate cancer therapy.

The application of Calypso Medical’s technology requires surgical placement of tiny “transponders” within the pelvis that can be used to track the actual position of the prostate at any point in time. These tranponsders can then communicate the precise position of the prostate to the computers controlling the radiotherapy beams to ensure that radiation is delivered with the greatest possible accuracy to the actual prostate, minimizing the potential for inadvertent and unwanted radiation of surrounding tissues. The entire process therefore involves both urologists in the placement (and subsequent removal) of the transponders and the radiotherapy specialists in use of the equipment to manage radiotherapy.

There is an extensive and growing literature on the use of the Calypso system that appears to be generally positive. However, again, we will really only be able to evaluate the clinical effectiveness and therapeutic value of this system in improving outcomes and reducing adverse effects when data is available over a period of at least 5 years.

We should conclude this update by noting that (in an ideal world) it seems likely that the combination of CyberKnife or RapidArc technology with the Calypso technology is potentially likely to offer patients the highest quality of outcome to external beam radiotherapy with the minimal impact on their day to day lives. Whether this form of radiotherapy for localized prostate cancer will be any more or less safe and effective than HDR brachytherapy (or any other form of treatment) may take longer to discover!

5 Responses

  1. Hi Mike,

    I do not totally agree with your take on the CyberKnife or Calypso. As a prostate cancer patient having to make a treatment choice my view may be biased. I was treated in 2008 with the CyberKnife. The most important consideration was the “net” quality (cure and and side effects) of life from treatment.

    Of all radiation treatments the CyberKnife is the only one with real time prostate tracking that adjust the beam to the target. This is a very important point as it improves the dose to the target while sparing the surrounding structures.

    It has been known for 20 years that higher dose/session delivered to prostate cancer is more effective (increases the kill factor). Data from HDR brachytherapy proves this point.

    The final results from any form of radiation takes 10-20 years. But you can compare the results at 1-3 years with the trend in cure rate and side effects from other radiation studies. I have not found a study that at 3 years shows higher cure and lower side effects than Study X but at 4, 8 10 years the trend changes. In simple words if the data at 3 years is better than treatment X it will also be better at 10 years.

    There are several studies with data at 3 years that are all very good and no worse than any other option for cure or side effects. The longest clinical trial at Stanford is now starting year six for the first patient, who is still cured and has no side effectts. No failures to date from this study.

    The fact that the treatment is 4/5 days is a bonus.

    Calypso is very new with no clinical data at one year showing it to be as good IMRT without Calypso. It does not have real time beam control.

    There is a dose trend in IMRT radiation that no one is addressing. In the last 10 years the dose has increased from 68/72 Gy to 80/86.4 Gy with no 2- or 3-year data showing side effect risk. The reason for this is that IMRT has an insurance/Medicare treatment code for payment that excludes the dose so doctors are able to increase the dose as they feel appropriate without data to support safety.

    Medicare can not be used to define standard of care today. The MMA of 2003 has rolled back the quality of care for Medicare patients, In the first half of 2008 the CyberKnife was covered for prostate cancer in CA, OK and TX; in 2009 It is not. The result is an increase in cost to the Medicare system and the patient. The CyberKnife is typically half the cost to Medicare compared to IMRT. For the patient, compare the cost of four or five trips for treatment vs 40.

    For Calypso to be have an equal tracking benefit to the present CyberKnife it has to control the beam delivery to the target in real time. The CyberKnife has gold seeds in the prostate that track movement real time in all axes, And it is needed as I saw the movement plot for my treatment session.

    Treatment results are improving from new technology (computer advances) that provides better imaging and better control of the beam to the target. This will continue and we will have better lives as a result.

  2. It is now January 2012. I have been diagnosed with localized prostate cancer. I am leaning towards CyberKnife or Calypso. Are there any more current data available regarding side effects of both?

  3. Dear Greg:

    “Calypso” isn’t a form of radiation therapy. It is a system used to target specific types of radiation therapy more accurately, and its ability to reduce side effects is entirely dependent on the skill of the radiation oncology staff who are planning your treatment and using the Calypso system to improve the accuracy of delivery of the radiation.

    CyberKnife radiation appears to have relatively lower levels of side effects than older forms of radiation therapy, but I am not aware of any “head to head” data that compare the side effects of CyberKnife radiation to those experienced by men receiving (say) relatively standard forms of IGRT/IMRT.

    All this is to say that, no, I am not aware of any recent data that would allow anyone to tell you with specificity that Calypso targeting of radiation is associated with less or more risk for side effects that CyberKnife radiation therapy.

  4. Hi Greg,

    As pointed out by Sitemaster “Calypso” is not a treatment. I would like to add the “Calypso” tracks the movement [of the prostate gland within the lower abdomen]; however, to my knowledge it will not adjust the radiation beam to stay on target. It only lets you know the target moved. It requires that someone adjust the beam if they “feel” it is necessary.


  5. Hi Greg,

    There are two published studies with 5-year data. Search with the following tags: “prostate cancer, five year, CyberKnife, Chris R. King MD, Alan Katz MD”.

    The study by Alan Katz, MD also compares the CyberKnife with other treatments, including IMRT. The Cyberknife is a clear winner from this data.

    I am a prostate cancer patient treated with the CyberKnife in May of 2008 and remain free of side effects with a PSA of 0.33.

    Best Wishes,


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