Heat as an Adjunct to the Treatment of Cancer
MANY cancers are more susceptible to destruction by heat than are the tissues they grow in. Heat acts synergistically, or at least additively, with radiation so that the combined effects of the two are greater than the effect of either one alone. These observations were reported half a century ago,1,2 but for the past 20 years little has been published on the effects of heat on cancer.
Our interest in the effects of heat started in June, I960, when, unaware of previously published studies, we noticed the regression of a mouse tumor that had been exposed to a temperature of 42 C. (107.6 F.) for two hours. The effect was reproducible. When we implanted S91 melanomas on the feet of DBA, mice we were able to destroy some of the resulting tumors by immersing the tumor-bearing feet for 30 minutes in water at 44 C. This temperature is only 111.2 F. or the temperature of a comfortably hot bath. In most cases there was no damage to the normal tissues of the feet. All of the animals that appeared to be cured 21 days after treatment lived longer than 90 days without recurrence.
The S91 melanoma is a moderately radioresistant tumor whose progressive growth is not controlled by radiation in doses up to 1000 r. But when this tumor was heated for 30 minutes at 44 C. and immediately treated with 1000 r there was complete regression in 20 of 25 mice. Twenty control mice, whose tumor-bearing feet were immersed . . .