New Technologies Add Precision to Prostate Cancer Treatments
Oct. 8, 2007 – An extra degree of precision will be added to radiation treatments for prostate cancer at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine following the installation of two new technologies.
The move to adopt these technologies was led by Jeff Michalski, MD, professor of radiation oncology at Washington University School of Medicine.
One of the technologies aids physicians during placement of radioactive seeds within the prostate and the other aids in targeting external-beam radiation. Both technologies will increase radiation treatment accuracy to better eradicate tumors and avoid injury to nearby tissues.
For more than 15 years, radiation oncologists have been using ultrasound scans to measure the size and shape of the prostate while the patient is in the operating room to determine where to insert radioactive pellets or seeds for treatment of prostate cancer. This type of specialized treatment is called brachytherapy.
But until now, the ultrasound probe used to obtain the prostate images was not linked directly to the treatment planning computer. That meant some of the changes in the prostate shape or position during treatment couldn't be taken into account, leading to less than optimal seed placement.
"Through a collaboration with two companies, Envisioneering Medical Products and Varian Medical Systems, we've integrated a unique ultrasound system with three-dimensional radiation planning," Michalski explains. "It has a stationary probe with a mobile transducer inside it, and the probe communicates directly with the treatment planning computer. That allows us to see in real time where the radioactive seeds are placed during the treatment to reduce the level of uncertainty."
A second advance allows real-time assessment and positioning correction during external-beam radiation therapy. Developed by Calypso Medical Technologies, this system employs beacons that transmit radio signals to a detector. A physician places the beacons into the prostate, and the beacons report the position of the prostate about 10 times per second as treatment progresses.
"Tests using this system showed that 15 percent of the time the prostate moves about a fifth of an inch during treatment," Michalski says. "Small shifts like this can have a profound impact on radiation delivery because we're giving a high dose of radiation shaped tightly to the prostate. If the prostate shifts too much, it will no longer be hit by the highest radiation dose. This system allows us to know in the midst of treatment if any corrections need to be made."
The system for intraoperative brachytherapy treatment planning is already in use. The Calypso system was installed at the end of September and will soon be available.
"Both technologies are geared toward lessening the amount of surrounding tissue that receives high doses of radiation and toward maximizing the dose at the tumor site," Michalski says. "We will be making comparisons of past treatment outcomes to those obtained with the new systems to see how well they perform."