Tumor response to arterial embolization hyperthermia and direct injection hyperthermia in a rabbit liver tumor model

Background and Objectives: It is possible to arterially embolize or directly inject liver tumors in small animal models with ferromagnetic particles that generate hysteretic heating on exposure to an alternating magnetic field. The objective of this study was to compare the response of liver tumors to arterial embolization hyperthermia (AEH) and direct injection hyperthermia (DIH). Methods: Ten rabbits containing experimental hepatic tumors were treated with AEH, and a second group of ten rabbits were treated with DIH. The tumors of both groups were heated to 43degrees to 50degreesC for 20 minutes. Tumor response, which was determined by measuring change in tumor volume and by comparison of tumor mass after treatment with the mass of untreated control tumors of the same age, was assessed 14 days after treatment. Results: All tumors treated with AEH decreased in volume by 50% to 94% (P = 0.005), and their average mass (median 1.73 gm) was significantly less than that of untreated control tumors (median 8.01 gm, n = 20; P < 0.001). Three of the treated tumors were completely necrotic, while the remainder were at least 80% necrotic. Nine of the ten tumors treated with DIH increased in volume by at least 143% (P = 0.01), and their average mass (median 5.68 gm) was not significantly different from that of the untreated control tumors (P = 0.56). Conclusion: These results indicate that AEH is more effective than DIH at moderately elevated temperatures. This is probably because the more widespread particle distribution that can be achieved using arterial embolization results in more extensive and complete treatment of the tumor. (C) 2002 Wiley-Liss, Inc.