For the study, researchers assessed 10 tumors in 10 patients who had lung tumors treated with CT-guided RFA and had PET scans both prior to RFA and following RFA. The researchers found that in seven out of 11 RFA treatments for the 10 patients, follow-up PET demonstrated persistent tumor activity. Two of the patients showed no activity on the follow-up PET, suggesting complete destruction of any active tumor. One patient had no definite change in the appearance of the mass, and another had a smaller lesion on follow-up PET.
"Usually, CT is used to assess tumor destruction, but CT cannot tell you whether a tumor is still alive--that is, actively metabolizing glucose--or dead in the area of destruction. It can also be difficult to assess how much of the ablated area is caused by an inflammatory reaction to the procedure. By using PET, the tumor cells that are still alive light up and the radiologist can better assess how much residual active tumor is left," said Jennifer Daly, MD, of the Newton-Wellesley Hospital in Newton, MA, and lead author of the study.
According to the researchers, without effective follow-up imaging, the radiologist has to gauge how successful it was based only on the patient's improvement in pain and maybe what is possibly seen on a post-ablation CT. "You don't really know for sure how much active tumor is destroyed unless you compare pre- and post-PET scans," said Dr. Daly.
The full results of the study will be presented on Monday, May 1, 2006 during the American Roentgen Ray Society Annual Meeting in Vancouver, BC.