The current standard practice is to devise radiation therapy targets based solely on computerized tomography (CT) scans, which produce detailed pictures of the size and shape of cancerous growths.
In a study in the April 15 issue of the International Journal of Radiation, Oncology, Biology, Physics, researchers show that adding data from positron emission tomography (PET) scans to structural CT data significantly enhances radiologists' abilities to precisely define the locations of tumors for radiation treatments. Radiologists use PET to get detailed information on tissue function and activity, enabling them to highlight such differences as the increased metabolic activity of a tumor.
For the study, researchers compared therapy plans designed by different physicians for 26 lung cancer patients. Two therapy plans were devised for each patient: A physician with access only to CT scanning results created one of the plans, while another physician independently created a second therapy plan based on combined data from CT and PET scans. Patients had non-small-cell lung cancer, the most common type of lung tumor.
"Adding the PET data to the analysis changed and improved the treatment plans 58 percent of the time," says lead investigator Jeffrey D. Bradley, M.D., assistant professor of radiation oncology. "PET-CT helped physicians more accurately identify where tumors were in patients, and that's very important to efficacy of treatment and to limiting side effects."
As an example of improved effectiveness, Bradley cited a patient whose tumor had caused a lung to collapse. With a CT scan only, physicians had identified a significant portion of the collapsed lung as tumor. However, with a combined PET-CT image, they were able to show that the tumor was much smaller.
Combined PET-CT scanning units, first devised approximately two years ago, are now available at hundreds of hospitals nationwide, according to Bradley.
"Papers like this are intended both to help change the community standard for how radiation treatment protocols are designed and to change insurers' willingness to pay for this new approach," Bradley says. "This is the next advance in radiology, and it could be very helpful to our patients."
Bradley is designing a multi-institutional follow-up study for the Radiation Therapy Oncology Group, a cooperative group funded by the National Cancer Institute.
Bradley J, Thorstad WL, Mutic S, Miller TR, Dehdashti F, Siegel BA, Bosch W, Bertrand RJ. Impact of FDG-PET on Radiation Therapy Volume Delineation in Non-Small-Cell Lung Cancer. International Journal of Radiation Oncology, Biology, Physics, April 15, 2004.
Funding from the Siteman Cancer Center supported this research.
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