Complications of radio-frequency thermal ablation.

Abstract

Editor: In the otherwise exhaustive review of clinical applications of radio-frequency (RF) thermal ablation of hepatic tumors by Dr Gazelle and colleagues (1), two kinds of RF complications that have recently appeared in the English-language medical literature (2,3) are not mentioned. At laparotomy, Mazziotti et al (2) found diaphragmatic invasion due to neoplastic seeding in two patients in whom previous RF ablation yielded incomplete necrosis. In my own experience (4), seeding of neoplastic cells occurred from a series of hepatocellular carcinoma nodules treated with an RF cooled-tip needle. Two years after RF treatment, two new 2-cm-diameter hepatocellular carcinoma nodules, one cephalic to the other, appeared along the pathway of the RF probe so that they could be imaged in the liver in the same scanning plane. That RF ablation entails a low but definite risk of seeding is unexpected, since it is common practice to withdraw the RF needle (at least the cooled-tip one) while it is still hot. Do Dr Gazelle and colleagues think that in some instances the needle-tip temperature is not high enough to kill neoplastic cells along the needle track and/or that viable tumoral cells may be moved into nontumoral tissue by means of the insulated shaft of the RF needle? Portal thrombosis with ensuing acute cavernomatous transformation, which we have recently reported (3), was even more unexpected, since results of experimental and clinical studies (5,6) on RF thermal ablation have indicated that the dispersion of heat because of blood flow (the socalled sink effect) represented the main cause of incomplete necrosis due to thermal ablation. Given that the treated metastatic nodule was at least 1 cm distant from the hepatic hilum and pretreatment study findings showed a patent portal vein. Therefore, we hypothesized that the heat was somewhat pear-shaped around the needle tip to reach the main portal venous wall, eliciting an inflammatory response (ie, phlebitis), which ultimately promoted thrombosis and cavernomatous trasformation of the portal trunk (3). Because of such a cascade of events, in some circumstances, the distribution of heat in vivo may be unpredictable and any vital structure whatsoever, even a large vessel, when suddenly struck with a blast of high temperature, may react with an inflammatory response, as already observed in other hollow viscera such as the gallbladder (7) and colon (8). In my opinion, any complication, even an unexpected one, following hyperthermia used for destroying hepatic tumors should be fully and accurately reported in detail so we can understand more fully the indications and hazards of all hyperthermia-based systems (RF, laser, microwave) in clinical practice.