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RESEARCH PRODUCT

Vascular Meets of Localized Hyperthermia

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description

When hyperthermia is applied in vitro, no fundamental differences can be seen between the response to normal and tumor cells. In vivo however, selective damage of tumor cells can be achieved and this phenomenon can be largely attributed to a number of characteristic properties of the blood vessels within solid tumors. Changes in blood flow induced by hyperthermia can influence the response of a tumor to heat either by affecting the delivery of heat through changes in heat dissipation or by a modulation of the tumor microenvironment which may in turn affect the thermosensitivity of tumor cells. Studies in experimental and human tumors suggest however that an accurate prediction of changes in blood flow during heating is not possible so that such changes cannot be used as a basis for the combination of hyperthermia with other therapy modalities. Even so, when the underlying mechanisms responsible for the antitumor effects of a combination of hyperthermia with either radiotherapy or chemotherapy are considered, it becomes evident that either an increase or a decrease in blood flow could potentially contribute to the cytotoxic effect. A further interesting approach is in the use of antivascular drugs or vascular-targeted photodynamic therapy in order to specifically reduce tumor blood flow prior to or during hyperthermia treatment. Experimental data suggest that a considerable enhancement of the antitumor effect can be achieved with this approach. By reducing heat dissipation, such an approach may in future also be of use in overcoming problems related to insufficient temperature increases frequently seen in the clinical setting.