Effect of high voltage electrical pulses on subcutaneous glioma tumours onrats

The antitumour effect of applied high voltage exponential pulses was invest igated on rats with subcutaneously implanted N32 brain tumours. Superficial tumours on the thigh were produced by the injection of 100 000 N32 glioma cells on Fischer-344 rats. Four weeks after inoculation, a solid tumour has grown to a size of about 1 cm located directly under the skin. Short elect ric high voltage pulses were given transdermally through stainless steel pl ate electrodes. Sixteen exponential pulses with initial field strength of 1 300-1400 V/cm and a time constant of 1 ms were delivered with a BTX600 devi ce at approximately one pulse per second. The treatment was repeated during 4 consecutive days. Tumour response was studied by measuring the length, w idth and thickness of the tumour with a slide-calliper and estimating the t umour volume as an ellipsoid. Animals (treated and controls) were sacrifice d when the size of the tumour had reached a predetermined value (5 cm(3)). In the first experiment this occurred after 50 +/- 4 days for the treated a nimals, excluding cured, compared to 40 +/- 1.3 for their controls and in t he second experiment after 64 +/- 24 days excluding cured animals compared to 37.6 +/- 3 for the controls. All treated animals showed an initial parti al or complete tumour remission within a few days after the end of the 4-da y treatment. Two out of ten treated animals were cured with no sign of recu rrence after 100 days. (C) 1998 Elsevier Science S.A. All rights reserved.