Background: Radiofrequency (RF)-induced tissue coagulation represents a new approach for the thermal destruction of tumors within the liver. The purpose of the current study was to 1) assess technique safety; 2) determine the extent and evolution of induced cellular damage; and 3) correlate the observed pathologic effects with radiologic studies.
Methods: Twenty-three tumors measuring </= 8 cm (19 colorectal metastases and 4 hepatomas) in 22 patients were treated with RF (range, 500-1550 milliamperes) using internally cooled electrodes. All treated tumors were resected to allow pathologic analysis. Eleven tumors were treated intraoperatively under ultrasonographic guidance and excised immediately. Twelve tumors were treated percutaneously using ultrasound or computed tomography (CT) guidance and subsequently were excised 3-7 days after ablation. Contrast-enhanced CT (n = 12) and magnetic resonance imaging (MRI) (n = 2) were performed after ablation of all percutaneously treated patients.
Results: Tumors treated intraoperatively did not demonstrate definitive coagulative necrosis. However, pathologic abnormalities suggestive of tissue injury were observed with hematoxylin and eosin staining, and absent cytosolic and mitochondrial enzyme activity suggested irreversible cellular damage. In contrast, specimens removed > 3 days after ablation showed definite, contiguous coagulative necrosis without intervening areas of viable tumor. CT and MRI scans demonstrated circumscribed hypodense, nonenhancing regions surrounding the electrode tract as early as 15 minutes after ablation. These corresponded within 2 mm to measurements of coagulation at pathology.
Conclusions: RF ablation is a minimally invasive and safe approach to the treatment of tumors in the liver. Tumors treated with RF energy do not immediately demonstrate coagulative necrosis, but do show evidence of irreversible cellular damage. The extent of tumor necrosis correlates closely with findings at contrast-enhanced imaging.
Copyright 2000 American Cancer Society.