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A treatment for prostate cancer that uses
microwaves to heat the prostate gland and destroy cancerous
cells was found to be safe and effective.
Researchers tested the therapy in 25
prostate cancer patients who had failed conventional radiation
therapy. The experimental treatment, known as interstitial
microwave thermal therapy, was delivered through five antennae
inserted beneath the skin under ultrasound guidance.
The doctors were able to heat the prostate
to the cell-killing
temperature of 55 degrees Centigrade (131
degrees Fahrenheit) while keeping temperatures in the urethra
and rectum at a safe 42 degrees C (107 degrees F). The procedure
required 2.5 hours of operating time, on average.
Before treatment, half of the patients
had PSA levels above 6.69 nanograms per milliliter (ng/mL).
Levels of PSA, a protein produced by the prostate, are used
to screen for cancer. A PSA level of less than 2-4 ng/ml is
considered normal.
At 24 weeks after therapy, 52% of patients
had achieved PSA levels of 0.5 ng/ml or less. An additional
40% of patients had PSA levels between 0.51 and 4 ng/ml, the
researchers note.
Patients also had biopsies -- a test
in which a sample of tissue is removed and checked for cancer
-- before the treatment and 24 weeks after treatment.
The
rate of cancer-free biopsies among the patients at 24 weeks
was 64%. There were no major complications with
the microwave treatment, and minor complications usually resolved
within 3 months of therapy.
Because prostate cancer varies in its
aggressiveness and patients with disease that has not spread
beyond the prostate can survive for long periods of time without
symptoms, the researchers suggest that a
treatment option with a low side-effect profile is highly
desirable.
However, they add, longer-term follow-up
in larger patient groups is required to confirm the results
before microwave therapy can be considered as an option for
treating prostate cancer.
The
Journal of Urology November 2001;166:1707-1714
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