Molecular Imaging News
May 8, 2006
FDG-PET Accurate for Evaluating Lung Tumor Destruction from Radiofrequency Ablation
American Roentgen Ray Society
FDG-PET can be used to assess the amount of tumor destruction after radiofrequency ablation (RFA)?the use of heat to destroy tumors?for the treatment of lung tumors and may provide more valuable information than CT alone, according to a new study.
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. In 7 out of 11 RFA treatments, follow up PET demonstrated persistent rim activity suggestive of a "shell" of residual neoplasm with a central area of photopenia related to the RFA or post ablation recruitment of vessels as an inflammatory response to the injury. Two patients showed no activity on the follow up PET, suggesting complete destruction of any metabolically active neoplasm. One patient had no definite interval change in the appearance or FDG-avidity of the mass when compared to the pre-procedure study. One patient on follow up PET had a smaller size lesion with the same activity, but without a photopenic center.
"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 were presented on May 1 during the American Roentgen Ray Society Annual Meeting in Vancouver, BC.