History
Surgery (“radical prostatectomy”) has been
the standard of care for prostate cancer for the last
50 years. Although effective, radical prostatectomies
are invasive and not without complications. Shortly after the discovery of
X-rays and radium at the turn of the century, physicians began to explore how
these modalities might improve survival and decrease potential side effects
from the radical surgery. Dr. Benjamin Barringer, chief of urology at what
is now known as Memorial Sloan Kettering Hospital, espoused the use of radium
needles for prostate cancer in 1917.
Initial radioactive seed
implantation was performed via “free-hand” technique,
using direct visualization of the prostate to guide
the radiation
oncologist with seed placement. However, the results
of this preliminary approach was hampered by suspect
dose distribution in the prostate.
In 1987, Dr. Blasko from
Seattle described a reproducible system to implant
radioactive Iodine seeds in the
prostate. This Seattle system employs a rectal ultrasound
probe to directly visualize the prostate and a plastic
template placed on the patient’s perineum (region
between the scrotum and the rectum). The template
guides the placement of the needles which are loaded
with radiactive seeds. This technique allows a reproducible,uniform
dose distribution to the prostate.
The physicians of ROCNJ have been performing this
procedure since 1997.
For Whom?
Prostate seed implantation is not for everyone. Treatment decisions are based
on important prognostic factors:
Stage
Gleason grade
PSA level
ROCNJ physicians have adopted
the Seattle group’s
criteria for implant selection. An ideal candidate
should have a PSA level <10, Gleason grade 6 or
less, with non-palpable disease.
The size of the prostate is also an important factor.
As a general rule, patients with prostate glands >60cc
are at increased risk for pelvic arch obstruction
and poor dose distribution. Androgen deprivation (hormone therapy) can be used
to shrink large prostates for several months to allow an optimal seed implant.
Patients who previously have had a vigorous transrectal
resection of the prostate (TURP) for benign prostatic
hypertrophy may not be ideal candidates for this
implant procedure. Higher rates of urinary complications
have been reported for these subset of patients.
Procedure
The first step in the process is an outpatient consultation with a radiation
oncologist. The radiation oncologist will advise on the implant option based
on the patient’s PSA, Gleason score, tumor stage, and other factors.
The second step is a planning
transrectal ultrasound (TRUS). A transducer is
placed in the rectum and
images of the prostate gland are obtained in 5mm
segments. Once the prostate is visualized, the radiation
oncologist works with the radiation physicists to
determine where the seeds should be placed. Through
the use of a treatment planning computer, a series
of “dose maps” called isodose curves
are generated. The goal is to deliver a dose of 150-160
Gy to the prostate with Iodine (I-125) and approximately
120 Gy with Palladium seeds (Pd-103). The seeds are “peripherally
loaded” to minimize the dose to the centrally
located urethra. This will minimize the risk of urinary
side effects.
The third step is the implant procedure. This is
performed in the operating room under either general
or spinal anesthesia. Under transrectal ultrasound
guidance, the prostate is implanted through the perineum
with needles loaded with radioactive seeds. Fluoroscopy
confirms the seed placement into prostate. Immediately
after the procedure, the patient is monitored for
several hours. Typically, the patient is discharged
to home on the same day.
The outcome of implantation is highly operator
dependent. As such, it is important for the radiation
oncologist to be experienced and proficient with
this procedure. The physicians of ROCNJ are among
the most experienced and have been instrumental in
pioneering this treatment option at their four centers.
Results
The Northwest Tumor Institute have documented excellent 10 year follow up data.
Their long-term outcome was comparable to external beam radiation therapy
and surgery. Although 20 year data is not yet mature, prostate seed implant
appears to be just as effective as surgery or external beam radiatherapy
for early stage prostate cancers.
Side effects
A common misconception among prospective patients is that prostate implantation
has fewer side effects than external beam radiation therapy. This indeed
is a misconception. Nearly all patients suffer from some urethritis. Urinary
retention requiring a temporary catheter occurs in 5% of the patients.
