Are seed implants for prostate
cancer effective?
By Michael O'Leary
SEATTLE-- Apr. 3, 2001
(Cancer Digest) -- Without clinical trials comparing "seed
implants" with standard treatments, the effectiveness of
the popular radiation therapy for prostate cancer cannot be determined,
say researchers who compiled data from several studies.
Writing in the April
issue of the Canadian Medical Association Journal, the research
team led by Dr. Juanita Crook, radiation oncologist at Princess
Margaret Hospital, Toronto, Ont. concludes there is not enough
data to determine whether brachytherapy, as it is called, is
effective.
"Results from
randomized trials with adequate follow-up are key in the evaluation
of new and emerging therapies such as brachytherapy," they
wrote. "At present, there is insufficient evidence to unconditionally
recommend the use of brachytherapy over current standard therapies."
The researchers, who
are members of a large cooperative study group called the Genitourinary
Cancer Disease Site Group of the Cancer Care Ontario Practice
Guidelines Initiative based a dozens of Canadian cancer centers,
analyzed data from 14 studies of seed implantation. None of the
studies, however, directly compare the treatment to standard
surgery or radiation.
Because the various
studies measured relapse differently, the researchers could not
determine a reliable relapse rate for all 14 studies. Also because
of the extended survival of cancer patients, none of the studies
included in the analysis was old enough to draw any conclusion
about whether seed implants prolong survival.
Crook's team did find
that treatment results in patients with small, low-grade tumors
with a blood test (PSA) indicating a low tumor volume were comparable
to those in patients undergoing surgery to remove the prostate
(radical prostatectomy).
Writing in an accompanying
editorial, Dr. J. Curtis Nickel, professor of Urology at Queen's
University, Kingston, Ont. calls the report a much needed reality
check.
"This carefully
researched overview, critical analysis and consensus report is
a breath of fresh air on a subject that is awash in unsubstantiated
claims, testimonials and hyperbole," Nickel says. "But
the report is also sobering. Only a small minority of patients
found to have prostate cancer meet the criteria for brachytherapy
suggested by the authors."
Brachytherapy seeks
to minimize damage to normal tissue that can occur with standard
radiation treatments delivered to the prostate from outside the
body. Instead, the radiation is delivered directly to the prostate
using tiny radioactive bits of wire inserted with a needle guided
by ultrasound.
The procedure is not
new, having been first tried in the early 1970s and abandoned
because of high relapse rates. However, improvements in radiation
technology and the use of computers and ultrasound to more precisely
place the "seeds" without surgery, renewed interest
in the procedure in the early 1990s.
Crook and colleagues,
conclude that as promising as the therapy appears to be for short-term
results, only randomized clinical trials will be able to determine
the long-term effectiveness of the treatment.
SOURCE: CMAJ 2001;164(7):975-81
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