JNM: PET/CT scan predicts recurrence after radiofrequency ablation

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PET/CT is a useful tool for predicting local recurrence in lung cancer patients treated with radiofrequency ablation (RFA), according to a study published in the December issue of the Journal of Nuclear Medicine.

RFA, which uses localized thermal energy to kill cancer cells, is increasingly used as an alternative treatment for patients unable to undergo surgery or other therapies to treat lung cancer.

"This study reinforces the utility of 18F-FDG PET imaging in cancer detection and followup while also providing new insight into factors that can be used for earlier prediction of recurrence after radiofrequency ablation of lung tumors," said the study's lead author Amit Singnurkar, MD, assistant professor of radiology and medicine at McMaster University in Hamilton, Ontario.

The five-year study between Dec. 17, 2003, and April 9, 2008, followed 68 patients with 94 pulmonary lesions, including metastases and primary lung cancers. By reviewing 18F-FDG PET/CT scans performed before and after RFA, researchers were able to determine several indicators that could help predict local recurrence.

A baseline 18F-FDG PET/CT study was performed by Singnurkar and colleagues no more than three months before RFA. The first postablation PET/CT scan was performed between one and four months after RFA; additional follow-up studies were obtained in some cases between six and 12 months after RFA.

Among pre-RFA scans, lesion size less than three centimeters and type of tumor (primary or metastases) were factors in determining potential for local recurrence. Standardized uptake value (SUV) less than eight was also a factor in pre-RFA scans, noted the researchers.

Treated metastases recurred less often than treated primary lung cancers. On postablation PET/CT scans, an unfavorable 18F-FDG uptake pattern at the site of the ablated lesion, high postablation SUV and progressive increase in 18F-FDG uptake during followup predicted local recurrence, according to Singnurkar and colleagues.

“PET findings suggestive of local recurrence may precede similar findings on CT, in many cases by six months or more in our patient population. This time interval may be clinically important because smaller tumors would be more amenable to retreatment with RFA or other intervention,” wrote the authors.

These findings may help in selecting patients for RFA and in tailoring patient management, including guidance of biopsies to sites of suspected recurrence and early retreatment. Therefore, 18F-FDG PET/CT should be essential in the pre- and posttreatment assessment of patients undergoing RFA for malignant lung lesions, concluded Singnurkar and colleagues.