Maury Regional and Vanderbilt medical centers are the first in Tennessee to use a new implantable device to measure the actual radiation dose delivered at a tumor site. Called the DVS^®-HFT, the dosimeter is the invention of North Carolina-based Sicel Technologies, which received clearance from the U.S. Food and Drug Administration in March for the dosimeter's use in treating breast and prostate cancer.

 

On May 6, Maury Regional used the dosimeter for the first time to treat a breast cancer patient, said W. Michael Sattasiri, MD, a radiation oncologist. While Maury Regional is initially using the device just for breast cancer treatment, Vanderbilt has opted for the alternative, introducing the technology exclusively to treat prostate cancer. Both eventually will adopt the other use.

 

Sattasiri explained that the dosimeter approaches radiation oncology "from a different angle." Currently, physicians calculate the necessary strength of the multiple radiation beams, using a CT scan to determine tissue density. Then diodes on the skin's surface ensure that the radiation delivered is at the level calculated.

 

"But we've never been able to accurately measure the amount of radiation exactly at the target in real time," Sattasiri said. "This is a better way to have quality assurance and checks and balances for each day of treatment, not just a calculated dose, but an actual dose."

 

A three-step measurement process is completed in a few minutes during treatment using a special reader to telemetrically collect radiation readings and transfer the results wirelessly and automatically to the system's software. The software processes patient data, treatment plans and dosimeter readings, producing a daily record of the dose delivered. As an added benefit, dose data from the DVS can be used collectively to evaluate the institution's adherence to national dose protocols.

 

For breast cancer treatment, the dosimeter generally is placed in the cavity resulting from a lumpectomy. Each dosimeter is inside a capsule that's 0.8 inches long and 0.08 inches across. The capsule is made of a biocompatible glass covered by a protective plastic coating and is not removed from the body after treatment for either breast or prostate cancer.

 

"This is a big step to actually be able to measure [the dose] in vivo. It just hasn't been done before," said Arnold Malcolm, MD, interim chair of the Vanderbilt Department of Radiation Oncology. "As radiation oncologists, we are clearly trying to understand in vivo what the doses we are delivering are doing to both the targets of interest, as well as the adjacent normal tissue."

 

A radiation oncologist for 35 years, Malcolm's expertise is prostate cancer. The dosimeter, he said, helps better ensure that the normal tissue of the anterior wall of the rectum and the posterior wall of the bladder are as protected as possible. Thus, he places one dosimeter in the center portion of the prostate and another along the posterior portion, which is close to the rectum.

 

Malcolm explained that the device has another advantage. Particularly when treating prostate cancer, physicians currently insert tiny pieces of metal at the site to help target the beams. Yet, the dosimeter serves the same purpose, thus eliminating the need to implant additional guidance markers. The dosimeter, he added, is very helpful when the prostate already has been removed, yet prostate-specific antigen (PSA) levels indicate the need for radiation therapy. That's because prostate removal changes the anatomy.

 

Both Malcolm and Sattasiri agreed the device has the potential to allow higher-dose radiation for a shorter treatment period because accuracy is so improved. Recent research has indicated that higher-beam doses over fewer treatments are highly effective in treating some tumors; thus, the approach is becoming more popular.

 

Michael D. Riddle, president and CEO of privately owned Sicel Technologies, said the DVS dosimeter is the result of research at North Carolina State University. "Next is lung, and we're at the moment designing the trial to get that through the FDA," he said. "We also have some other products in the pipeline that are a couple of years away that could potentially enable us to look at the efficacy of chemotherapeutic drugs, as well."