It has been
estimated that the lifetime risk for a man in Western society of
developing microscopic prostate cancer is around 30%, 10% of which will
develop into potentially dangerous cancer.
The
challenge, therefore, is to accurately distinguish these dangerous cancers
from those considered insignificant. Although strides have been made in
prognosis through evaluation of tumor stage, grade and volume, DNA
analysis and molecular markers, the call to accurately predict important
cancers has not been completely answered In this setting, the decision to
choose and undergo treatment is, at times, confusing and difficult for the
uninformed patient. Today, a minimally invasive effective treatment
alternative, called prostatic interstitial radiation seed implantation, or
brachytherapy, exists and is appropriate for many early stage, low to
moderate grade prostate cancers.
Improvements in the way radiation is delivered to the
prostate is considerably changing the treatment of clinically localized
(organ confined) prostate cancer, expanding patient's options and,
perhaps, narrowing the indications for radical surgical removal of the
prostate. This form of radiation therapy provides an alternative to
watchful waiting and radical surgical removal of the prostate for
organ-confined disease and may render a definitive "cure". While enormous
strides continue to be made in external beam radiotherapy, no modality has
benefited more from technological advances than radiation seed
implantation. Transrectal ultrasound, or TRUS, and computed tomography, or
CT imaging techniques, improved forms of seeds, and computerized dose
calculations for accurate radiation dosing have revived and refined an old
technique.
Previously,
radiation seeds were implanted through an open abdominal incision into the
prostate when organ confined cancer was suspected. This technique was
abandoned due to high local recurrence and metastatic recurrence rates.
These failures were due in large part to under dosing whole areas of
cancer due to poor geographic placement and distribution of seeds. With
modern brachytherapy, seeds are delivered through a needle placed into the
perineum, with no incision, using either CT pre-planning and/or ultrasound
guidance. This significantly reduces distribution errors.
It appears,
from information gathered over an eight to nine year period, that seed
implantation reduces death rates from prostate cancer and improves local
disease control better than external beam radiotherapy and nearly as well
as surgical removal of the prostate for certain types of cancer.
Interstitial seed implantation is carried out as a same
day or overnight procedure, usually under a general anesthetic. An
ultrasound probe is placed in the rectum and is used to guide needle
placement of radiation seeds into the prostate. The needles are placed
through a template grid completing a three-dimensionally preplanned
distribution of seeds and dose.
Using
transverse ultrasound images the needles are advanced into the gland until
seed distribution is optimized in each plane through the gland. Seeds are
then deposited under ultrasound as needles are withdrawn. CT scans are
performed post-operatively to evaluate for any areas of under dosing.
Usually, the bladder catheter is taken out the same day or left in
overnight. This is, therefore, a truly minimally invasive approach.
It is important, in deciding upon treatment with seed
implantation, to select only a patient for whom this technique would be
appropriate. Candidates for the interstitial implantation of seeds have
clinically localized disease, adequate life expectancy to make a cure
worthwhile, no colorectal disease, no recent TURP (transurethral resection
of the prostate), and absence of lower urinary disease. Complication rates
have been reduced from between 5 and 20% in the surgical implantation
approach, to less than 5% with the incisionless needle placement, and are
superior to complication rates of external beam therapy. Some patients,
however, do experience acute problems of urination, including urgency and
frequency during the seeds' active life. This typically lasts a few days
to a couple of weeks. Only 10% of these cases require treatment with
medication or temporary bladder catheterization. Potential late
complications include urinary incontinence in less than 1% of patients
(although there is a 12% incontinence if seeds are placed after TURP), a
4% incidence of urethral stricture and a 2% chance of proctitis (rectal
irritation and diarrhea).
The primary dilemma in prostate cancer management
continues to be uncertainty in differentiating those cancers confined to
the prostate, and those which have spread (and are therefore not amenable
to this form of treatment). At present, seed implantation has no proven
effect on disease outside the prostate. In prostate confined disease, the
results of modern seed implantation has been encouraging, especially when
compared to outcomes of the old, retropubic implantation technique. In
general, encouraging results have been seen at 5 years, with success rates
for stages T1 and T2 of around 96% and 89% respectively. Post-treatment
biopsy results at five years were equally encouraging with 87% disease
free after modern seed placement. Seeds are not, however, appropriate for
all cancers, whether organ confined or not. This further emphasizes the
need for careful patient selection. Still, despite short term success,
long term data and randomized head to head trials against the traditional
organ-confined treatments, surgical removal of the prostate and external
beam radiotherapy, are not yet available. In comparable external beam
series, seeds seem to have better disease free survival statistics than
external beam recipients. Caution must be used in endorsing seed
implantation in all cancer scenarios, since history has shown a late
propensity for recurrence of cancer after all forms of radiotherapy.
Presently, despite its potential complications, the surgical treatment
option offers more assured "cure" potential for accurately staged (T1 or
T2) disease.
From a urologist's perspective the decision whether and
how to best treat prostate cancer is dependent on three factors: disease
extent or stage, patient age, and general health (factoring in other
ongoing illness). No one fact simplifies this complicated decision making
process. To reiterate, one third of men have small foci of prostate cancer
but only 10% will develop into clinically significant disease. However, 80
to 90% of cancers detected by elevated PSA (prostate specific antigen) are
clinically important and warrant treatment in men with a 10 year or
greater life expectancy. So, when is it necessary to treat prostate
cancer? For now, this is best answered by a urologist informing patients
about research results based on stage and grade of the cancer. The patient
must weigh the negative side effects of treatment options against the
likelihood of success. Given this degree of uncertainty, there is clearly
a place for a minimally invasive treatment option with minimal side
effects for cancers which are of questionable significance.
Radiation
seed implant not only fulfills this need, it may eventually replace
surgical removal of the prostate as the curative "gold standard" for
clinically confined, low moderate grade prostate cancer. This is the
current trend. Only time will answer whether the short term successes of
seed implantation are followed by long term "cures".
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