FDG-PET adds information for RFA surveillance

Functional imaging techniques such as FDG-PET can detect hepatic tumor activity following radio-frequency ablation therapy long before structural imaging surveillance can, according to researchers at the University of Pennsylvania. Such early feedback may enable clinicians to fine-tune patient management after tumor therapy.

"Reliance on anatomic images as evidence for detection of the disease, response to treatment, and recurrence may lead to inaccurate conclusions," said Dr. Hongming Zhuang, an assistant professor of radiology at Penn.

Zhuang and colleagues examined 13 patients with histories of malignant liver tumors who had been treated with RFA. The researchers retrospectively studied the FDG-PET scans administered to the patients after the treatment. They performed concurrent MR scans of eight patients, CT scans of six patients, and two FDG-PET scans of one patient.

FDG-PET detected all new tumor activity in the patients after treatment. PET diagnoses were confirmed on clinical follow-up. Recurrent tumors appeared at the ablation site in eight patients, and new metastases in three.

"More and more, we are realizing that structural images such as those provided by CT or MRI alone may not allow for optimal assessment of disease activity in almost any clinical setting," said Dr. Abass Alavi, a professor of radiology at Penn. "This is particularly true when dealing with interventions like chemo-embolization or RFA, where changes that occur due to these treatments may significantly alter the anatomy at the site and the surrounding tissues."

In the patients who underwent both MR and PET imaging, MRI positively identified three of the seven cases detected by PET and indicated a negative or equivocal finding for the other four cases. Of the six patients imaged by both CT and PET, four had positive PET scans and two had positive CT scans.

The study appeared in the March 2003 issue of Clinical Nuclear Medicine.

Impressed by the performance of FDG-PET in this application, Alavi and colleagues are looking at the management of patients with other diseases that respond well to medical and radiation treatments.

"Lymphomas stand out as a great model. Response to treatment as judged by a change in size of the involved nodes or other structures can be misleading and may result in mismanagement of these patients," Alavi said.