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Hyperthermia is indicated for use alone or in conjunction with radiation therapy in the palliative management of certain solid surface and subsurface malignant tumors (i.e., melanoma, squamous- or basal-cell carcinoma, adenocarcinoma, or sarcoma) that are progressive or recurrent despite conventional therapy.
Clinical studies using BSD's hyperthermia systems to deliver hyperthermia in conjunction with radiation therapy have shown that 83.7% of patients had some tumor regression, 37.4% of patients had a complete tumor regression and 24.5% had a greater than 50% tumor regression. Clinical data obtained in BSD's studies on hyperthermia and radiation therapy demonstrated that approximately 10% of patients experienced burns and blistering from heating, 8% experienced pain, 4% experienced ulceration from rapid tumor necrosis, and 2% experienced ulceration from placement of temperature sensors and rapid tumor necrosis.
Microwave hyperthermia is a non-ionizing form of radiation therapy that has been shown to improve the results of radiation therapy for the treatment of some recurrent and progressive tumors. Hyperthermia has been shown to destroy cancer cells by raising the tumor temperature to a "high fever" range. Because the body's means of dissipating heat is through cooling from blood circulation, sluggish or irregular blood flow leaves cancerous tumors vulnerable to destruction at elevated temperatures, unlike surrounding healthy tissues which have normal, efficient blood cooling systems. Scientists attribute the destruction of cancer cells at hyperthermic temperatures to damage in the plasma membrane, the cytoskeleton and the cell nucleus. Cancer cells may be vulnerable to hyperthermia therapy particularly due to their high acidity caused by theeir inability to properly expel waste. Hyperthermia attacks acidic cells, disrupting the stability of cellular proteins and killing them.
The combination of hyperthermia and radiotherapy may increase the effectiveness of radiotherapy alone in the palliative treatment of some tumors. Hyperthermic temperatures increase blood circulation in tumors as a response to the stimulus of heat. Tumor tissues that have low blood flow are resistant to radiotherapy but are sensitive to hyperthermia, while tumor tissues with high blood flow are sensitive to radiotherapy making the two treatments complementary.
The complementary interaction of hyperthermia combined with radiation is due to the independent cytotoxic effects of hyperthermia combined with its radiosensitizing effects.
Laboratory studies have shown that hyperthermia potentiates radiotherapy.ii Hyperthermia and radiation therapy kill cancer cells at different stages of growth. Hyperthermia increases blood flow, resulting in improved tissue oxygenation and thus increased radiosensitivity.ix Hyperthermia also interferes with cellular repair of the DNA damage caused by radiation.i The basis for the additive effect of hyperthermia on radiotherapy comes from the ability of hyperthermia to kill cells that are hypoxic, have a low pH, and are in the S-phase of division, which are all conditions that make cells radioresistant.viii Randomized studies have not shown an increase in either acute or late toxicity of radiotherapy from the addition of hyperthermia.ii
i Dahl O, Dalene R, Schem BC, Mella O. Status of clinical hyperthermia. Acta Oncol. 1999;38(7):863-73.
ii Van der Zee J. Heating the patient: a promising approach Annals of Oncology 2002;13:1173-1184.
iii Falk MH and Issels RD. Hyperthermia in oncology. Int J Hyperthermia 2001;17(1):1-18.
iv Kapp DS. Hyperthermia: rationale and clinical applications. Syllabus: Refresher Course 310, Presented at 38th Annual ASTRO Meeting. Los Angeles, CA. October 29, 1996.
v Jones EL, Oleson JR, Posnitz LR, et al. A randomized trial of hyperthermia and radiation for superficial tumors. J of Clin Oncol 2005;23(13): 3079-85.
Patient receiving hyperthermia treatment
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vi Wust P, Hildebrandt B, Sreenivasa G, Rau B, et al.Hyperthermia in combined treatment of cancer. Lancet 2002;3:487-497.
vii Hehr T, Wust P, Bamberg M, Budach W. Current and potential role of thermoradiotherapy for solid tumours. Oncologie 2003;26:295-302.
viii Raaphorst GP. Fundamental aspects of hyperthermic biology. In Field SB, Hand JW (EDS): An Introduction to the Practical Aspects of Clinical Hyperthermia. London: Taylor and Francis 1990; 10-54.
ix Song CWM, Shakil A, Griffin RF, Okajima K. Improvement of tumor oxygenation status by mild temperature hyperthermia alone or in combination with carbogen. Semin Oncol 1997; 24: 626-632.
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