This group of procedures can be divided into three categories based on temperature. The normal body temperature, 98.6 degrees Fahrenheit, is 37 degrees centigrade. All of the temperatures discussed below are in centigrade.
Hyperthermia, the mildest approach, uses temperatures that are less than 45 degrees—which probably isn’t hot enough to accomplish major relief of obstruction. In thermotherapy, tissue is heated to temperatures greater than 4s degrees—at which point some cellular protective mechanisms are overwhelmed, and normal cells are destroyed. To make sure only the BPH tissue is destroyed, temperatures in the region are monitored closely during this treatment. Thermal ablation techniques can produce the hottest temperatures of all—above 60 degrees—and are usually performed using high-intensity focused ultrasound, transurethral microwave therapy, interstitial radio frequency waves, and lasers.
An important fact about thermal therapy is that—except for contact laser prostatectomy—the BPH tissue in the targeted area is killed but not removed. One problem with this is that many men experience acute swelling immediately after these procedures and may need a catheter until the dead tissue is re-absorbed by the body, or is sloughed into the urethra and washed away in urine. (Another problem is the lack of tissue samples for pathologists to examine.) This marks a big difference from surgical procedures such as TUR, where the obstructive tissue is extracted, and the patient generally can urinate well immediately afterward.
As noted, temperatures in hyperthermia range from 41 degrees to 45 degrees. As heat treatment goes, these temperatures are rather lukewarm. Hyperthermia is not painful, and it can be performed as an outpatient procedure; it usually involves multiple treatments. It can be done in two ways—trans-rectally, by a probe inserted into the rectum, and transurethrally, by an instrument inserted through the penis into the urethra.
The technique has only recently undergone randomized, placebo-controlled studies, in which patients were treated without knowing whether the heat generator was activated. The largest recent study has demonstrated no significant objective improvement in urinary flow rates.
Why is this? For more than a century, doctors have known that heat can kill cancer cells. Hyperthermia as a treatment for BPH grew out of techniques used to treat malignancies, including prostate cancer. It can be given to cancer patients along with radiation because rapidly multiplying cancer cells in certain phases of division are particularly susceptible to heat.
The basic problem here is that normal cells respond differently than cancer cells; and just because a technique works on cancer cells, it doesn’t necessarily follow that it will work in normal tissue. BPH tissue—though growing—is benign, not cancerous, and it just isn’t that sensitive to these temperatures. Scientists who have looked under the microscope at BPH cells heated to 45 degrees have trouble telling them apart from BPH cells that have not been treated. Hyperthermia isn’t hot enough to kill BPH tissue. The tissue reacts, certainly, but the results are not permanent, and the injured tissue eventually recovers. So at this point, using temperatures less than 4S degrees should be considered an ineffective solution to a long-term BPH problem.
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