Prostate Cancer Treatment Advance -- Calypso System Uses Miniature GPS Transponders

by Amber Smith | The Syracuse Post-Standard | 03.14.2009

The prostate moves, ever so slightly, with the normal process of food moving through the body.

No biggie - except when the prostate is cancerous and you're aiming radiation at it. You want to be acccurate, so as to limit damage to surrounding tissues.

One of the newest ways to treat prostate cancer is available at Syracuse's Upstate Medical University. Installed in late October, the Calypso has been used successfully on four men, says Dr. Jeffrey Bogart, a radiation oncologist.

"So far, the tracking has been amazing," he says.

Before radiation is delivered to kill the cancer cells, patients have three transponders, the size of rice grains, implanted within the prostate. The transponders act like global positioning systems, communicating through wireless electromagnetic circuits with the Calypso tracking system. This allows Bogart to precisely position the patient before radiation, and continuously monitor the tumor's position during the radiation session.

Syracuse urologist Kenneth Hoogs has heard of Calypso, but so far has not recommended patients for the procedure.

"It sounds like it's a technological improvement," he says. "They're still using the same types of radiation. This is just a guiding system."

Exactly.

"It's an advanced form of what we call image-guided radiotherapy," Bogart says.

It's not for every man with prostate cancer.

Some are not candidates for the Calypso because they have replacement hips, leg prosthesises or cardiac pacemakers that interfere. There are size limitations, too, he says.

"Typically we're looking at men with early prostate cancer, prostate cancer that has not spread," Bogart says. So many treatment options exist - surgery, radioactive seed implants, external beam radiation -- that "sometimes it's very difficult to make up their minds."

Patients have to weigh the risks and benefits with their doctor, and Bogart suggests talking with both a urologist and a radiation oncologist to go over options.

Calypso has risks.

"The prostate lies right between the bladder and the rectum. To have some urinary symptoms or changes in bowel habits would not be unusual," Bogart says, but the chances of those changes being temporary are good, with the radiation being so accurate.

He says many health insurers are covering Calypso and that the price of radiation is the same whether it's delivered through Calypso or another method. The Calypso has the additional cost of the transponders and their implantation, done in a procedure similar to that of a prostate biopsy.

Does it work better than other therapies?

Hoogs answers: "It's a new thing. I don't know how effective it is. The FDA (Food and Drug Administration) approves it, but that doesn't mean a whole lot. It just means it's not going to harm anybody. If it's going to make a significant difference, someone would have to do multiple studies, and those things take years."

Lots of studies are under way. Bogart says Upstate is involved in some of them, looking at the dosing of radiation and how many weeks it should be continued. In addition, the same sort of technology is being studied to track tumor movement in other areas of the body.

Copyright The Syracuse Post-Standard 2009