Strong synergy of heat and modulated electromagnetic field in tumor cell killing.

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Strahlenther Onkol. 2009 Feb;185(2):120-126. Epub 2009 Feb 25.

Andocs G, Renner H, Balogh L, Fonyad L, Jakab C, Szasz A.
1"Frederic Joliot Curie" National Research Institute for Radiobiology and Radiohygiene, Budapest, Hungary.
BACKGROUND
AND PURPOSE:
: Hyperthermia is an emerging complementary method in
radiooncology. Despite many positive studies and comprehensive reviews,
the method is not widely accepted as a combination to radiotherapy.
Modulated electrohyperthermia (mEHT; capacitive, electric field
modulated, 13.56 MHz) has been used in clinical practice for almost 2
decades in Germany, Austria and Hungary. This in vivo study in nude
mice xenograft tumors compares mEHT with "classic" radiative
hyperthermia (radHT).
 
MATERIAL AND METHODS: : Nude mice were
xenografted with HT29 human colorectal carcinoma cells. 28 mice in four
groups with seven animals each and two tumors per animal (totally 56
tumors) were included in the present study: group 1 as untreated
control; group 2 treated with radHT at 42 degrees C; group 3 treated
with mEHT at identical 42 degrees C; group 4 treated with mEHT at 38
degrees C (by intensively cooling down the tumor). 24 h after
treatment, animals were sacrificed and the tumor cross sections studied
by precise morphological methods for the respective relative amount of
"dead" tumor cells.
 
RESULTS: : The effect of mEHT established a double
effect as a synergy between the purely thermal (temperature-dependent)
and nonthermal (not directly temperature-dependent) effects. The solely
thermal enhancement ratio (TER) of cell killing was shown to be 2.9.
The field enhancement ratio (FER) at a constant temperature of 42
degrees C was measured as 3.2. Their complex application significantly
increased the therapeutic enhancement to 9.4.
CONCLUSION: : mEHT had a
remarkable cancer cell-killing effect in a nude mice xenograft model.