Therapeutic prostatic thermotherapy

#The present invention relates to the heat treatment of prostate disorders, including, but not limited to, benign prostatic hyperplasia, prostatitis, and prostatic malignancy.

#Use of heating or energy radiating devices, particularly microwave radiating devices, to administer heat for the treatment of various diseases of the prostate have been demonstrated to provide efficacious treatment of various prostate conditions (Devonec et al., Monographs in Urology, 13, 77-95 (1992); De La Rosette et al., J. Urology, 157, 430-438 (1997); Devonec et al., J. Endourology, 5, 129-135 (1991); Bernier et al., Curr. Opin. Urol., 7, 15-20 (1997)). Research has indicated that the cellular transformations brought about by raising tissue temperatures above certain levels can be used therapeutically. At temperatures above 45° C., thermal damage has been found to occur to cells, even when the exposure to the elevated temperatures lasts for even a short period of time. Thermal therapy has been defined as the process of heating tissue to greater than 45° C. to create necrosis. Both normal and abnormal cells respond to thermal exposure. Accordingly, therapies using heat have relied on healthy tissue regeneration after the delivery of a “thermal dose.” A thermal dose is a quantity which is indicative of the biological impact of elevated temperature maintained for a period of time. For the purposes of the present invention, thermal dosages can be calculated according to the method of Sapareto et al., International Journal of Radiation Oncology, Biology, Physics, 10, 787-800 (1984), except that the breakpoint of 45° C., rather than 43° C. is used for non-malignant tissues. That is, for the purposes of the present invention, thermal dose measured in Equivalent 45° C. hours is equal to the sum of the products of one half of the treatment temperature in excess of 45° C. times the duration at that time, or

#t=final

#FIG. 1 is a block diagram of a urethral insertable electromagnetic radiation applicator system according to an embodiment of the present invention.

#FIG. 2 is a block diagram of the temperature control system and the microwave applicator of the system illustrated in FIG. 1.

#FIG. 3 is a flow chart of a temperature control program for regulating the temperature of body tissue heated by the microwave applicator of FIG. 2.

#The present invention provides a method of heat treating a patient's prostate tissue and devices, programs, and systems useful in practicing the present inventive method.

#Surprisingly, it has now been found that the maximum urethral temperature that can be tolerated by patients to whom narcotic analgesics or general anesthesia have not been administered exceeds the previously art-accepted maximum of 45° C.-47° C., under selected conditions. It has also now been found that the side-effects which have been reported to accompany high temperature treatment of the prostate are substantially reduced by use of the method of the present invention when the temperature is kept below about 57° C. Moreover, it has been surprisingly discovered that preservation of the prostatic urethra is not an important parameter of the thermotherapy of the prostate. On the contrary, the urethra and the urethrally proximal portions of the prostate are the tissues in which heating is desired in the present inventive method. Thus, the present invention provides a method of heat treating a patient's prostate tissue wherein the temperature of the prostate tissue is raised from an initial temperature below the destination temperature, to a destination temperature in the range of from 49° C. to almost 57° C. The destination temperature is maintained for a period of time sufficient to administer a sufficient amount of heat to achieve a therapeutic effort on the prostate.

#It has now been found that by allowing a patient to acclimatize to elevated urethral temperatures the patient's threshold of pain, with or without anti-inflammatory analgesics, is elevated to about 60° C. Thus, the present invention provides a method of prostatic thermotherapy wherein the maximum urethral temperature is raised to an elevated temperature which exceeds the previous art-accepted maximum by elevating the method temperature in such a manner so as to allow the patient to acclimatize the temperature elevation procedure. The rate at which the temperature can be raised from 37° C. to the range of about 42° C. and 46° C. can be relatively rapid. In keeping with the inventive method, it is desirable for the rate at which temperature is elevated from about 44° C. to the destination temperature to occur more slowly. Further, the rate of rise in temperature preferably decreases as the maximum urethral temperature approaches the destination temperature. In general, the rate of increase in temperature according to the present invention varies between 1° C. per 0.5 minutes to 1° C. per 15 minutes. In order to allow better patient acclimatization, the rate of change in the temperature preferably does not exceed 1° C. per minute, and more preferably does not exceed 1° C. per 2 minutes. However, it is desirable to physician and patient to minimize the amount of time required for therapy. In order to reduce the amount of time required to acclimate the patient to elevated urethral temperatures, the rate of temperature rise can be increased to 1° C. per 10 minutes near the destination temperature and to about 1° C. per 2 minutes at the lower temperatures. The total time to raise the urethral temperatures from 37° C. to the destination temperature preferably ranges from 15 minutes to 2 hours, and more preferably is from 20 to 45 minutes. Moreover, it will be appreciated that the temperature rise can be continuous or discontinuous (i.e., “stepped”).