GPS System Helps Treat Prostate Cancer
Same Navigational Technology Used in Cars Allows More Precise Radiation Treatment
By SAMI B??G, M.D.
ABC News Medical Unit
Feb. 12, 2007
When he was diagnosed with prostate cancer at age 69 in September of last year, Robert Heinkel wanted to make sure that he got the best treatment with minimal side effects.
An engineer by profession, he began learning as much as he could about the disease that now afflicted him.
"First I took about 30 days and did a lot of research," said Heinkel. "My whole objective was to pick a therapy that had the least side effects."
What he found was a procedure that uses the same GPS (Global Positioning System) technology that is in cars -- except in this case, the technology helps doctors navigate around tumors to make radiation treatment much more effective.
Heinkel traveled to the Swedish Cancer Institute in Seattle, Wash., where he became one of the first patients in the world to take advantage of this technology, known as the Calypso 4D Localization System. The technology was recently approved by the FDA for use in patients.
Navigation System Allows "Smart" Radiation
Radiation therapy is nothing new; in fact, according to figures from the American Cancer Society, it is used to treat about one million cancer patients in the United States each year.
However, one downside of radiation treatment is that the beam sometimes misses the tumor and irradiates nearby organs and tissues. In prostate cancer treatment, this radioactive "friendly fire" can cause complications like impotence, urinary incontinence and rectal bleeding.
And due to the nature of the prostate, doctors sometimes have difficulty drawing a bead on these tumors.
"The prostate can move a few millimeters from day to day, or even during the same daily treatment," said Dr. Majid Mohiuddin, assistant professor of radiation oncology at the University of Maryland Medical Center in Baltimore.
Mohiuddin says further damage to surrounding tissues can occur because cancer doctors will usually treat the prostate with a margin of extra radiation around the borders of the treatment area just to ensure that the entire tumor has been irradiated.
The new tool aims to sidestep this problem by precisely navigating the beam of radiation to hit the tumor -- and only the tumor.
"When we treat patients it is very important to get very precise radiation to minimize any complications," said Dr. Peter Grimm, director of the Seattle Prostate Institute at the Swedish Medical Center.
"This is a revolutionary development in the treatment of cancer with radiation therapy, and it is going to vastly improve technical precision."
The technology uses tiny electromagnetic sensors, called beacon transponders. Doctors implant the transponders, each about the size of a small grain of rice, into the prostate prior to treatment.
The tiny devices send coordinates to a computer, which continuously monitors the position and motion of the prostate. The system alerts clinicians when the prostate is not properly aligned with the radiation beam, allowing them to adjust its path.
Other cancer experts are hopeful that the technological advance could represent a major step in how doctors navigate their ways around tumors during radiation treatment.
"Until now we have used ultrasound and other technology to guide us when treating cancers, but this adds another level of precision," said Dr. Rashid Haq, clinical assistant professor of radiation oncology at SUNY Upstate Medical University in Syracuse.
"It seems with this new technology you have the ability to pinpoint a tumor's location with greater accuracy and continuously monitor its position in a real-time fashion during radiation treatment."
Technology Could Apply to Other Cancers
While this is the first time the technology is being used, experts say that it has implications beyond prostate cancer.
"Any tumor that moves could be tracked in this manner," said Mohiuddin. "The greatest benefit would be in lung cancer, where tumors move because of the patient's breathing."
And judging from initial interest, the technology may have the potential to become a widely available option for cancer treatment.
"Leading cancer centers around the country have shown a high degree of interest in this and we are talking to a number of cancer sites," said J. Nelson Wright, executive vice president and chief technology officer for Calypso.
But for the time being, Heinkel says he is simply glad that the navigational system made his cancer treatment more bearable.
"Having an engineering background, specifically a radiofrequency background, I was very interested in understanding the technology and the functionality of the system," said Heinkel.
"But as a patient I am just happy that so far I have had no side effects. It has been a very benign experience."