Experimental Hyperthermic Isolation-Perfusion Using cis-Diamminedichloroplatinum(II)

The intent of this study was to determine whether or not local control and/or cure of rabbits bearing the VX-2 carcinoma could be achieved with regional hyperthermia and chemotherapy. A model of isolation-perfusion used c/s-diamminedichloropla- tinum(ll) (DDP). Five different experimental groups were studied, each group receiving progressively smaller tumor inocula and shorter treatment intervals. Although local control and cure improved as the tumor inocula became smaller and treatment interval became shorter, there was no benefit demonstrated when compared to sham-operated animals. DDP appeared to be well tolerated in animals perfused as normothermic temperatures. However, animals perfused at hyperthermic temperature with DDP experienced necrosis of normal as well as neoplastic tissue, resulting in early demise of the animal. This final observation suggests that the amount of DDP utilized in clinical isolation-perfusion should be approached Experimental Design. The intent of the study was to determine whether or not local control and/or cure of tumor-bearing animals could be achieved with regional hyperthermia and chemotherapy. However, matters of critical importance were the size of the tumor inoculum and the interval between inoculation and therapeutic manipulation. It became apparent early in the course of the study that the tumor was extremely virulent and metastasized soon after inoculation. Therefore, 5 different experiments were contrived, each based on the results of the previous effort to optimize size of inoculum and treatment interval in order to maximize treatment effects. Ninety-seven rabbits were used in this study. The 5 experimental groups were comprised of the following tumor inocula and treatment intervals: (a) 1 x 107 cells, 7-day interval (n = 15); (b) 3 x 106 cells, 7- day interval (n = 21); (c) 3 x 106 cells, 4-day interval (n = 18); (d) 1 x 106 cells, 7-day interval (n = 21); and (e) 1 x 106 cells, 4-day interval (n = 22). Animals underwent perfusion at normothermic temperatures (37°) or hyperthermic temperatures (42°)with and without the addition of DDP to the perfusate. These experimental groups were compared to tumor- bearing animals which were either untreated or underwent a sham operation. The sham operation consisted of the induction of general anesthesia, an incision over the femoral artery and vein, and the ligation of these vessels supplying the limb carrying the tumor. Experimental Tumor. The tumor utilized in this study was the VX-2 rabbit carcinoma, a derivative of a Shope virus papilloma. This is a highly virulent tumor with a propensity for early mA©tastases.A single passage of the tumor was used. A solitary tumor was grown in the flank of a New Zealand albino rabbit. When it reached a size of approximately 6 cm in diameter, it was harvested under sterile conditions, minced in Roswell Park Memorial Institute Tissue Culture Medium 1640 (Grand Island Biological Co., Grand Island, N. Y.), and filtered through a sterile fine mesh gauze. The resulting single-cell suspension was counted, and the concentration was adjusted to 3 x 107 cells/ml. The final cell suspension was made up in a freezing medium composed of 75% Roswell Park Memorial Institute Tissue Culture Medium 1640, 15% fetal calf serum, and 10% dimethyl sulfoxide. The suspension was aliquoted, frozen