Pawel Mertyna MD,PHD, Presenter: Nothing to Disclose

Himaja Peddi MBBCHIR, Abstract Co-Author: Nothing to Disclose

Zhengjun Liu MD, Abstract Co-Author: Nothing to Disclose

Nadeer Pirani MD, Abstract Co-Author: Nothing to Disclose

Muneeb Ahmed MD, Abstract Co-Author: Nothing to Disclose

S. Nahum Goldberg MD, Abstract Co-Author: Nothing to Disclose

To determine the extent of differences in tissue heating necessary to achieve tumor ablation when RF is used alone or in combination with liposomal doxorubicin in two animal tumor models.

R3230 mammary adenocarcinoma was implanted subcutaneously in 60 female Fischer rats. Tumors (1.4-1.8cm diameter) were randomized into groups: (a) conventional monopolar RF alone (1cm tip, 70±2°C), and (b) RF ablation with liposomal doxorubicin (Doxil, 1mg IV, 30min post-RF). At least 3 animals in each group were ablated for 2.5, 5, 7.5, and 10min. Thermocouples placed 1.5-7mm from the active electrode measured temperatures throughout the ablation to construct thermal maps of tumor heating. As a second model, 9 subcutaneous canine venereal sarcomas (4.2-6.2 cm diameter) were randomized to: (a) RF ablation alone (1cm internally cooled electrode; 12min; impedance-controlled mode), or (b) 1mg/kg IV Doxil 30min after RF ablation. Temperature measurements during RF ablation were performed 5-20mm from the electrode. For both models, the extent of complete ablation and temperatures at the ablation margin were calculated and compared by means of ANOVA statistics.

Combination of RF and Doxil increased tumor destruction vs. RF alone (p<0.001, both tumor models). In the rat, coagulation diameter was time dependent and ranged from 5.2±0.4mm at 2.5min to 10.6±0.6mm at 10min for RF ablation alone, and from 7.4±0.4mm to 12.4±0.5mm for RF combined with Doxil (exponential r² of 0.94 & 0.98, respectively). For dog tumors, coagulation diameter was 22±2mm for RF alone vs. 30±2mm for RF plus Doxil (p<0.001). The threshold to achieve ablation in the rat was lowered by 4.4±0.34°C by administering Doxil (52.4±1.4°C vs. 48±0.3°C at 5 minutes, p<0.001). For the dog, the threshold for complete ablation was lowered with the addition of Doxil from 65.7±1.2°C to 56.8±1.3°C (p<0.001).

Tumors can differ substantially in their sensitivity to RF heating. IV administration of liposomal doxorubicin increases RF coagulation in solid tumors compared to RF ablation alone and further accentuates tumor sensitivity to heating.

S.N.G.: Research supported in part by NCI 1R01CA112533-01; and Valleylab, Boulder, CO, medical consultant Valleylab

Mertyna, P, Peddi, H, Liu, Z, Pirani, N, Ahmed, M, Goldberg, S, Marked Differences in Tumor Sensitivity to RF Ablation with and without Liposomal Chemotherapy.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4412753.html