If ever there was a case of
the treatment being potentially as devastating as the
disease, it's prostate cancer. The dilemma facing the
newly diagnosed prostate cancer patient is well known.
If left alone, this slowest-growing of all tumours might
do no great harm in the patient's remaining lifespan,
but removal by either surgery or radiation will very likely
cause impotence and could lead to urinary incontinence.
Ten years ago, the then-new technique
of cryoablation — destroying the prostate by freezing
— offered lower rates of incontinence, and a second
chance to patients not helped by radiation. Cryoablation
won widespread acceptance, but it did nothing to solve
the problem of impotence.
Proponents of cryoablation argued
that better imaging and biopsy methods might one day
turn their technique into a high-precision tool capable
of killing tumours while sparing the nerve bundles essential
to erection.
POTENT
NEW Tx
That day has arrived according to research presented
a few weeks back at the Society of Interventional Radiology's
Annual Scientific Meeting in New Orleans. Dr Gary Onik,
medical director of surgical imaging at Florida Hospital
Celebration Health, reported a new biopsy method that
maps localized prostate tumours. With this new method,
he says, focal cryoablation is now possible.
"Treating only the tumour instead
of the whole prostate gland is a major and profound
departure from the current thinking about prostate cancer,"
said Dr Onik at the meeting. "Focal cryoablation changes
the whole picture in terms of complications, and the
cancer control is as good as with any other treatment."
Dr Onik's team presented the results
of focal cryoablation in 42 patients aged 55-75. After
an average four years of followup, 40 were apparently
cancer-free with stable prostate specific antigen (PSA)
levels. Three of these patients had a recurrence of
cancer in an untreated part of the prostate. Cryoablation
of those secondary tumours was successful, according
to Dr Onik.
Of 32 patients who were potent
prior to the procedure, only 22% became impotent afterwards.
That compares with impotence rates of about 50% with
radiation therapy and 75% with radical prostatectomy.
The procedure was carried out on an outpatient basis,
with most of the men resuming normal activities within
two weeks.
FOCUS
IS KEY
The key to focal cryoablation is pinpointing the tumour.
Prostate tumours are much less visible to standard imaging
techniques than breast tumours. Transrectal ultrasound
is generally used more as a rough guide than a precise
map.
For the new technique, called 3D
global biopsy mapping, a fine grid is placed over the
perineum and biopsy cores are removed through the skin
rather than the rectum. About 75 cores are removed compared
with about 10 in a standard biopsy. Each is correlated
to its place on the grid, creating a three-dimensional
map of the prostate.
Ultimately, focal cryoablation
will stand or fall by the accuracy of this technique.
Killing tumours with supercooled gas is not, in itself,
a technical challenge. "This biopsy technique allows
us to map the location of the tumour with tremendous
precision and has the potential to greatly affect the
decisions we make about treating prostate cancer," claims
Dr Onik.
Annual Scientific Meeting, Society
of Interventional Radiology, Mar 31-Apr 5, 2005
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