Calypso 4D Localization® and Tracking with Beacon® Transponders during External Beam Radiation Therapy

The Seattle Prostate Institute believes that treatment for prostate cancer should be individualized for each patient's condition rather than one treatment for all.  For patients interested in seed implant brachytherapy, it is often possible to successfully treat with seeds alone. However, for patients with more advanced or aggressive disease, it may be advisable to treat with external beam radiation (EBRT) in addition to seed brachytherapy. In some cases it is advisable to add hormone therapy to the mix as well. Unfortunately, when external beam is added to brachytherapy, there may be a small but significant increase in side effects and risk of complications compared to seeds alone. The primary concern is for rectal damage and a greater risk of impotence. Any steps that can be taken to minimize the chances of injury with external beam are highly desirable.

What’s the problem with the way external beam radiation (EBRT) is delivered at other centers and why is the Calypso  system tracking with implanted Beacon® Transponders important?

First, a little background. Although there can be several reasons for adding EBRT to brachytherapy, the main one is to treat areas slightly outside the prostate that may contain prostate cancer and are just beyond the reach of seed radiation. In the instance of combined EBRT and seeds, the EBRT is delivered as a daily treatment, Monday through Friday, for about 5 weeks. It’s delicate work to effectively treat the prostate and the outside areas without giving too much radiation to the rectum, bladder, or bulb of the penis. Over the last 10 years there have been improvements in our ability to accurately deliver external radiation to the prostate. These advances have been in two general areas.

First, computer based techniques of radiation delivery have been developed so that the radiation beam can be shaped much more tightly and precisely.  These approaches are usually termed 3D conformal radiotherapy and more recently, Intensity Modulated Radiotherapy (IMRT). Today, nearly all radiation oncology centers, including the Seattle Prostate Institute, utilize this technology for prostate treatment. The second advancement has been in the area of accurately identifying and monitoring the location of the prostate within the body. This is where the development of Calypso Medical's Beacon® transponder technology provides an important new breakthrough.

At first glance, it seems puzzling why this should be an issue....the prostate sits in front of the rectum and below the bladder and can easily be seen on a simple CT, ultrasound or MRI scan, so why don’t you know where it is? What we have learned is that the prostate is not always in the exact same place from day to day and even from minute to minute. The prostate can be pushed back and forth as much as an inch by stool or gas in the rectum and amount of urine in the bladder. Also, the normal muscle contraction of the rectum that comes and goes can move the prostate in unpredictable ways. Therefore, it does little good to use a very tight delivery of radiation such as IMRT if it is not aimed accurately at the prostate every day.

Doctors have known about this prostate movement problem for years and have devised methods to address it. The most common approaches have been the use of gold seed markers that can be seen on an x-ray, the use of daily ultrasound scanning, or the use of a CT scanner built into the radiation treatment machine. With each of these approaches the prostate position is assessed daily before the radiation treatment is delivered and the “aiming” of the machine can be adjusted if necessary. While this is certainly an improvement over the “point and hope” approach of the past, these methods only partly solve the problem.

The problem is the fact that these methods only measure where the prostate is before the treatment, not during the daily treatment delivery. A recent investigation has shown that changes in prostate position can happen in seconds and it is usually more than 15-20 minutes from the time the prostate position is measured and the completion of the radiation treatment. This means that the prostate could unknowingly move out of position and the radiation could miss the prostate and hit the rectum, bladder, or bulb of the penis.

Calypso Medical is a Seattle-based company that developed the Beacon® transponder and 4D Localization System to solve one of the most difficult problems with external beam radiation therapy....moving organs. With this technology, three tiny radio-frequency transponders are inserted into the prostate (see: How Beacon® transponders work) and they transmit the exact position of the prostate many times a second to an external receiver. So doctors know the exact position of the prostate before, during and after each treatment....GPS for the Body®.

Using this technology you can be much more confident that the prostate is positioned directly in the path of the sophisticated IMRT radiation beam each and every time you receive treatment. After intensive testing and investigation, this device is now cleared by the FDA for clinical use. Since Seattle Prostate Institute physicians were intimately involved in the conception and development of this technology, we are the first in the world to bring this technology to the daily treatment of prostate cancer patients.

The ultimate promise is that patients who are treated with IMRT-based EBRT in conjunction with the Calypso system will receive the most reliable and accurate treatment possible. This accuracy should further reduce radiation side effects on the rectum and bladder while maintaining the excellent cancer cure rates that have been demonstrated with the combination of EBRT and brachytherapy for patients with more aggressive disease.

The Calypso Medical technology is part of a broad spectrum of treatment options for prostate cancer.  Men with cancer confined to the prostate whose treatment may require the use of external beam radiation therapy are the best candidates for the Calypso 4D Localization System, providing you do not have a pacemaker or artificial hip.  If you have prostate cancer, all available options should be discussed with your physician.  To learn how this important new technology can be used for your treatment, and to discuss other treatment options, please schedule an evaluation at the Seattle Prostate Institute.

To see the King 5 News report on GPS for the Body, please click here

How Calypso Beacon® Transponders Work                                                                     Calypso Medical Website