New Radiation Therapy Tools Target Prostate Tumors More Accurately

Jason Merrill

Hiram Gay, MD

March 18, 2011 – Radiation oncologists with the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine have a new tool in the treatment of prostate cancer that not only targets tumors better but also can stop treatment automatically if the tumor moves due to a full bladder or rectum.

The prostate is located between the bladder and the rectum. Depending on whether those organs are full, the prostate can move from day to day and also during traditional radiation treatment.

“It can be quite substantial and could account for missing the prostate target and not delivering the prescribed dose of radiation, which could result in a failure of the treatment,” says Hiram Gay, MD, a Washington University radiation oncologist at Siteman.

Using a new technology that gives what some refer to as a “GPS” of the prostate, Gay and his colleagues can monitor the position of the prostate in real time throughout treatment.

"The prostate is practically invisible to the X-rays that we take on a daily basis, so we have a surrogate way of finding out where the prostate is by implanting what are called beacons,” Gay says. “These three transponders serve as a GPS to triangulate where the prostate is located.”

Recently added is a technology called “gating” that allows providers to set limits for motion. If the area in the prostate that is being targeted moves beyond a preset level, radiation delivery is halted automatically. Previously, providers manually performed this task.

“Let’s say the patient takes a deep breath," Gay says. "The machine will actually turn off if the prostate moves if it moves outside the radiation zone. It’s been shown in multiple studies that even though we think we’re hitting the prostate 100 percent of the time, without these types of technologies, we risk underdosing the prostate. And in some patients, that may make the difference between curing the cancer or not curing the cancer.”

Siteman is the first facility to use the gating technology with real-time tumor tracking. Both technologies are manufactured by Calypso Medical Technologies Inc.