Effects of hyperthermia on the central nervous system: What was learnt from animal studies?
J. Haveman A1, P. Sminia A2, J. Wondergem A3, J. van der Zee A4, M. C. C. M. Hulshof A1
A1 Department of Radiotherapy, Academisch Medisch Centrum, Amsterdam, The Netherlands
A2 Department of Radiation Oncology, Division Radiobiology, VU Medical Center, Amsterdam, The Netherlands
A3 Department of Occupational Health and Risk Assessment, Leids Universitair Medisch Centrum, Leiden, The Netherlands
A4 Department of Radiation Oncology, Hyperthermia Unit, Erasmus MC–Daniel den Hoed Cancer Center, Rotterdam, The Netherlands
Animal studies show that nervous tissue is sensitive to heat. Although inter-species variations may play a role, the data indicate that the maximum heat dose without obvious complications after localized hyperthermia in regions of the central nervous system (CNS) lies in the range of 40–60 min at 42–42.5°C or 10–30 min at 43°C.
Expression of thermotolerance after a ‘conditioning’ heat dose was clearly observed in the spinal cord of rodents and the thermotolerance ratio's (ratio between heat doses with and without conditioning required to obtain a certain defined effect) were high, ∼2. Ann's NOTE: Sorry we do not know what this symbol means, but it appeared in the article as we saw it online.
The thermotolerant state of CNS is shown to protect also against other types of injury as well: pre-treatment of rats with hyperthermia protected against spinal cord ischemic injury. During the rather long period required for temperature elevation which is inherent to WBH, some degree of thermotolerance may develop.
The correlation between thermotolerance and hsp70 induction in CNS is obvious. Heat, at least if applied shortly after X-rays, enhances the response of nervous tissue to radiation. Data on the combined effects of X-ray irradiation and hyperthermia on rodent spinal cord clearly show that the radiation response can be enhanced with a factor of 1.1–1.3.
There are no clear experimental data indicating an increase in adverse effects specific to the CNS after localized or whole body hyperthermia as a result of combined treatment with chemotherapy.
International Journal of Hyperthermia
Volume 21, Number 5 / August 2005
Pages: 473 - 487
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