Histopathologic and Immunohistochemical Features of Tissue Adherent to Multitined Electrodes after RF Ablation of Liver Malignancies Can Help Predict Local Tumor Progression: Initial Results

doi:10.1148/radiol.2491071752

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Vascular and Interventional Radiology

Histopathologic and Immunohistochemical Features of Tissue Adherent to Multitined Electrodes after RF Ablation of Liver Malignancies Can Help Predict Local Tumor Progression: Initial Results¹

Constantinos T. Sofocleous, MD, Rodrigo G. Nascimento, MD, Lydia M. Petrovic, MD, David S. Klimstra, MD, Mithat Gonen, PhD, Karen T. Brown, MD, Lynn A. Brody, MD, Anne M. Covey, MD, Raymond H. Thornton, MD, Yuman Fong, MD, Stephen B. Solomon, MD, Lawrence H. Schwartz, MD, Ronald P. DeMatteo, MD, and George I. Getrajdman, MD

¹ From the Section of Interventional Radiology (C.T.S., R.G.N., K.T.B., L.A.B., A.M.C., R.H.T., S.B.S., G.I.G.), Department of Pathology (D.S.K.), Department of Epidemiology and Biostatistics (M.G.), Department of Surgery (Y.F., R.P.D.), and Department of Radiology (L.H.S.), Memorial Sloan-Kettering Cancer Center, 1275 York Ave, Room H-118, New York, NY 10065; and Department of Pathology, New York University, New York, NY (L.M.P.). Received October 3, 2007; revision requested December 21; revision received January 28, 2008; accepted March 26; final version accepted April 3. Address correspondence to C.T.S. (e-mail: sofoclec{at}mskcc.org).

Purpose: To determine whether histopathologic and immunohistochemicalfeatures of tissue adherent to electrodes after radiofrequency (RF)ablation of liver malignancies can help predict local tumor progression(LTP).

Materials and Methods: Institutional review board waiver and informedconsent were obtained. Histologic and immunohistochemical examinationsof tissue adherent to electrodes after RF ablation of liver malignancieswere performed, with application of proliferation (Ki-67) and apoptosis(caspase-3) markers. Clinical and technical information were prospectivelycollected for an HIPAA-registered database. Medical records and imagingwere reviewed to determine LTP for treated tumors smaller than 5cm in diameter. LTP-free and survival rates were assessed with Kaplan-Meiermethod; differences between groups assessed with permutation log-ranktest. Multivariate analysis assessed with Cox regression for factorsrelated to LTP.

Results: Sixty-eight malignant tumors treated with RF ablation wereidentified. Fifty-five tissue specimens were classified as coagulationnecrosis (CN), thermal artifact only, or tumor cells positive forcaspase-3/negative for Ki-67; and 13 as viable tumor cells (Ki-67positive). Mean tumor size was larger in viable (3.4 cm) than inCN (2.5 cm) group before treatment (P = .01). For viable and CN groups,LTP occurred in 12 (92%) of 13 and 16 (29%) of 55 specimens, respectively;1-year LTP-free rates were 0% and 74%, respectively (P < .001).Multivariate analysis confirmed that viable cells comprise independentrisk factor for LTP (P < .001). The odds of LTP is six times greaterin viable group compared with CN group for tumors 3–5 cm (hazardratio: 5.9, 95% confidence interval: 2.4, 14.5) and 10 times greaterfor tumors smaller than 3 cm (hazard ratio: 10.1, 95% confidenceinterval: 1.7, 57.5). Median survival was 32.7 months.