Logistics of a Permanent Implant
Frequently Asked Questions about Permanent Radioactive
Seed Implants for Prostate Cancer
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Main FAQ Page
Prostate Cancer Issues
Logistics of a Permanent Implant
Side Effects of a Permanent Implant
Potency after a Permanent Implant
Radiation Safety after Permanent Implant
Pros and Cons of Implants
Follow-up after a Permanent Implant
What kind of physician typically performs the radioactive seed implantation
procedure and in what kind of setting?
Radioactive seed implantation is usually performed in our hospital setting
by a team of physicians consisting of a radiation oncologist, urologist
and a radiation physicist. This is a highly operator-dependent procedure
and does reflect on the experience of the team.
What skill is required when performing a prostate implant?
Achieving good results with brachytherapy requires substantial technical
skill. The technical and clinical results can vary substantially from one
practitioner to another. The dependence on physician's skill is much greater
than for external beam radiation therapy. The necessity for such substantial
skill has caused some to criticize prostate brachytherapy, because not all
patients will obtain the same results as those treated by physicians who
specialize in prostate brachytherapy. Performing good implants, requires
skill, attention to detail and tolerance for tedium*. There is also
a significant dependence on manual dexterity and familiarity with the physics
of brachytherapy. Prostate brachytherapy requires a substantial time investment
by the physician and should be performed by those physicians who are willing
to devote such time.
At Thomas Jefferson University we have devoted a great of time and energy
to our implant program which is recognized nationally and internationally
for the research that has resulted from our work. A list of some of the
publications describing our research can be found by clicking on the button
labeled Publications from TJU.
* Prostate Brachytherapy made complicated by Kent
Wallner, John Blasko, and Michael J. Dattoli. SmartMedicine Press, Seattle
Washington, 1997.
What should a patient look for in an implant program?
The implant process is the summation of the skill and expertise of the
team which includes a radiation oncologist, urologist and radiation physicist.
Clearly, radioactive seed implants are a highly operator-dependent procedure
which can have a steep learning curve. In general, one should look for a
program with a proven track record. In addition, all patients should have
a post-implant CAT scan performed with the coverage of the prostate specified
(e.g., 90 % of the prostate covered by the 150 Gy isodose line). Without
performing a post-implant CAT scan, there is no means to adequately evaluate
the implant, and the exact dose delivered will never be known. Standard
X-rays are not helpful in this situation.
How is the planning procedure performed?
Imaging of the prostate is the first step. This will allow a three-dimensional
reconstruction of the prostate/urethra and its relationship to the rectum.
It will also allow a calculation of the volume of the gland. The imaging
of the prostate is performed with a CT and ultrasound. These images are
then reconstructed utilizing software developed at Thomas Jefferson University
and a three-dimensional model is created. The radiation oncologist and physicist
use this model to determine the exact location of each seed. After a careful
review of the treatment plan by each member of the team, (physician and
physicist), a coordinate map of the prostate is created which describes
the location coordinates for needle and seed. This treatment plan is used
in the operating room and followed closely. Additional seeds are available
in order to make adjustments at the time of the implant.
Why is a CT scan for pubic arch evaluation performed?
An important determination when ascertaining whether a patient is technically
appropriate for seed implantation is an evaluation of the position and shape
of the pubic arch. This is a structure approximately six inches below the
navel. The implant requires placing needles into the prostate which is located
behind the pubic arch. If the pubic arch is too narrow, and the prostate
too large, it can be difficult to place the needles into prostate and they
will hit bone. Evaluation of potential pubic arch interference is important
because it can determine whether a patient may require hormonal therapy
prior to an implant. Hormonal therapy can shrink the gland significantly
to make the gland implantable. This is done for approximately 3 months to
acheive maximal downsizing.
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Pubic Arch Interference
For a larger view, Click Here |
What is the length of the procedure and the type of anesthesia?
Typically, the procedure takes about 11/2 -2 hours and is done under
general anesthesia. We prefer general anesthesia because our patients seem
to tolerate it quite well. Generally, there is no sensation of pain after
the procedure and painkillers are unnecessary.
Are Palladium seeds better than Iodine seeds?
One of two different types of radioactive materials (or "radioisotopes")
may be used in a given case. In some cases, seeds of iodine-125 ("I-125")
are used while seeds of palladium-103 ("Pd-103") may be used in
others. Both radioisotopes emit very low energy radiation which is primarily
absorbed in the treatment area or "target" tissue immediately
surrounding the seed. These isotopes differ somewhat in their radioactive
"half lives".* (see below) The seeds, which hold the radioactivity,
are constructed of stainless steel. The seeds themselves are small - approximately
0.5 millimeters (less than two one-hundredths of an inch) in diameter -
about the thickness of the pencil lead for a refillable pencil. Seed lengths
may range from 1.2 millimeters (less than five one-hundredths of an inch)
to 3.0 millimeters (less than twelve one-hundredths of an inch), although
roughly 2 millimeter lengths are used in most cases. Between 75 and 100
seeds are actually implanted in a typical case. The amount of radioactivity
(or "activity") in each seed is measured in units of milliCuries
("mCi"). Usually seeds containing about 0.70 mCi in each are used
(although this amount may vary). The activity of a seed is sometimes loosely
referred to as the source or seed strength. There is no proof that one type
of seed is better than another and clinically we believe the results to
be equal. The doses and seed strengths, in fact, are prescribed to produce
the same biologic effect.
*
| 1 inch |
= 2.54 cm |
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= 25.4 mm |
Why perform a CT scan after the procedure?
The CT scan is performed to confirm the placement and location of the
seeds. The CT scan also allows the implant team to perform a dose calculation.
The post-implant dosimetry acts as a permanent record of the implant. It
is similar to having a pathology report after a surgical operation, describing
positive margins, etc. It also gives the implant team another means of evaluating
the quality of the implant. On very rare occasions additional therapy
may be suggested.
What medications do you prescribe after the procedure?
Depending on a patient's urinary dynamics we may prescribe an alpha-blocker
(Cardura TM, Flomax TM or Hytrin
TM after the procedure. These are medications that
relax the smooth muscle of the prostate, allowing for improved urinary flow.)
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