Hyperthermia in cancer therapy where are we today and where are we going英文电子书.pdf

341 HYPERTHERMIA IN CANCER THERAPY: WHERE ARE WE TODAY AND WHERE ARE WE GOING? RICHARD A. STEEVES, M.D., PH.D. University of Wisconsin Medical School Wisconsin Clinical Cancer Center Madison, Wisconsin A LTHOUGH CLINICAL hyperthermia was used decades ago with impressive anecdotal reporting, much of the enthusiasm 10 years ago for trying hyperthermia in cancer therapy was based on information emanating from the laboratory.2 Some transplantable tumors in mice were destroyed by time- temperature combinations that did not permanently damage normal tissue.3 Additional information from the laboratory is summarized below. Two distinct effects of heat may contribute to the control of cancer: first, heat kills cells directly, and second, heat sensitizes cells to ionizing radiation or drugs. Both effects ofheat may be observed at temperatures between 40.5TC and 45TC, but direct cell killing is usually weak below 43TC. Some neoplasms seem inherently more sensitive to heat than the normal cells from which they arise, but this is not true of all neoplasms.4 It is generally recognized that hyperthermia has greater potential benefit in cancer therapy when coupled with another treatment modality such as ionizing radiation. Mechanisms by which heat may sensitive cells to ionizing radiation are: reduced ability ofheated neoplastic cells to repair sublethal and potentially lethal damage;5 increased thermal sensitivity of hypoxic-acidotic tumor cells;6 complementary cell sensitivity to heat and radiation during different phases of the cell cycle. WHERE ARE WE TODAY? At the present time clinical hyperthermia is often used with limited doses of ionizing radiation to pa