How long ago did doctors start performing prostate seed implants as treatment for prostate cancer?
Prostate brachytherapy has been performed since the 1960s. Modern techniques were introduced in the early 1980s when Dr. Holm (in Denmark) developed the first transrectal ultrasound-guided transperineal prostate seed implants (TPPI). Physicians from the USA then learned this technique and began performing TPPI in the USA in the late 1980s. The procedure has undergone major technical innovations in the last five years.
How does the implant treat the cancer?
If you think about the way that ripples extend concentrically from a pebble tossed in a pond, you can imagine how the gamma radiation extends out from each seed. Seeds are strategically placed such that the radiation of each seed interact with that of other seeds in a manner that gives the optimal dose of radiation to the prostate while minimizing the radiation dose to the other body tissues.
How does the radiation kill the cancer cells?
The radiation does not actually kill the cancer cells outright, but causes damage to the genetic material (DNA) within the cells. If the treated cancer cells were biopsied and viewed through a microscope, they would appear alive and active. The destruction occurs when these injured cells attempt to reproduce by the process of mitosis (cell division). They self-destruct, die, and are eliminated by the normal body mechanism that eliminates dead cells. The idea is to give a high enough radiation dose to destroy the reproduction capabilities of every last cancer cell.
Are normal tissue and organ cells also killed?
Yes, normal cells of the tissues and organs that receive the radiation dose from the prostate seed implant are also injured. Some of the normal cells can repair the damage while others will die in a manner similar to that described above. Fortunately, however, cancer cells are much more sensitive to radiation than healthy normal cells and one has many more normal cells than cancer cells in the area being treated, and it is by this mechanism that every last cancer cell can be destroyed while sparing enough normal cells for the normal body tissues and organs to recover. It is the damage to the normal body tissues and organs that causes the side effects of the treatment.
Why do prostate seed implants cause less damage to the normal body tissues such as the rectum and bladder than external beam radiation therapy?
Radioactive implant seeds give off a very low energy gamma radiation that travels for a very short distance. When the seeds are strategically placed, it is possible to minimize the damage to the normal body tissues in the rectum, bladder, urethra, and erectile mechanism
When will the commonly observed side effects of prostate seed implant therapy occur?
Some of the side effects from radiation therapy (either external beam radiotherapy or prostate seed implant therapy) occur within days or weeks of the treatment and are called the acute side effects. Other side effects, known as late side effects, may not appear for six or more months after the treatment.
What is the risk of the seed implant therapy affecting your ability to have erections adequate for satisfactory sexual intercourse?
If you already have erectile dysfunction and either are not able to have erections or have only partial erections that are not sufficient for intercourse, more likely than not you will have erectile dysfunction after the prostate seed implant. If your erections are barely rigid enough for intercourse, or if they do not sustain adequately, you will have a very high risk of erectile dysfunction after the prostate seed implant therapy. There are possible treatment options for erectile dysfunction that you may wish to pursue. If you have reasonable good erectile function prior to the prostate seed implant, you will have about a 60% to 80% likelihood of having adequate erections after the prostate seed implant. Nearly all the treatment options will work well for those whose erections were good prior to prostate seed implant but impaired afterwards.
Is it safe to be around other individuals or sleep with your partner after the prostate seed implant?
Since the radiation from radioactive seeds used for prostate implantation is so weak, very little radiation leaves your body and you are not a radiation risk to those around you. From a radiation safety perspective, you may sleep in the same bed with your partner. Sexual intercourse may be resumed within the first few weeks after the seed implant. Since there is a remote risk of ejaculating a seed, you should wear a condom for the first few times you have intercourse. If you notice a seed and can retrieve it, please do so using tweezers, placing the seed in aluminum foil, about 6x6 inch, wrap it tightly and return it to your center to be disposed of safely.
However, It is strongly recommended that you avoid close contact with children and pregnant women for a couple of months following a prostate seed implant. In the future if you seek medical help in any institution or doctor’s office, related to your implant or not, please inform the provider of the date of your seed implant and the name of your Radiation Oncologist.
Please remember to call your Radiation Oncologist if you are in pain or discomfort after the implant or have any questions about your post implant care.
What are prostate implant seeds?
The medical devices commonly referred to as seeds are really small individual radioactive sources. They are 4.5 mm (3/16 in.) in length and 0.8 mm (1/32 in.) in diameter. Each consists of an outer titanium shell (seed) into which the radioactive isotope (Iodine–125 or Palladium–103) is then inserted, along with radiopaque markers (so that the individual seeds can be seen on x-ray films and with fluoroscopy), and microscopically laser-welded shut to keep the radioactive material within the device.
How are Iodine-125 and Palladium-103 produced?
While Iodine-125 is a naturally occurring radioactive element, the I-125 used in the implant seeds is made in a nuclear reactor. Palladium-103 used in radioactive seeds can be produced either in a nuclear reactor or in a high-energy particle accelerator (cyclotron).
What kind of radiation do the implant seeds emit?
Radioactive seeds emit low-energy gamma rays (which are like x-rays) and low energy beta particles (which are like electrons). However, the titanium shell of the seed filters out nearly all the emitted radiation except that which is desirable for the treatment of cancer. What the seed ultimately emits is predominantly a low-energy gamma ray that is a very weak type of x-ray.
Is there any advantage of one isotope over the other?
To date, there is no clear answer as to whether one type of radioactive seed is better than another. The two most commonly used radioactive seeds are Iodine-125 and Palladium-103 seeds. While many physicians have an opinion as to which type of seed is best, it is important to recognize that this is, in reality, an unanswered medical question. Excellent results have been demonstrated with both isotopes.
What is the potential benefit of using radioactive seeds?
Since I-125 and Pd-103 seeds emit a very weak gamma ray, it is possible to strategically place them in and around the prostate in a manner that minimizes the radiation dose to normal tissues and organs such as the urinary bladder, urethra, nerves and blood vessels that allow for erectile function, and rectum while optimizing the dose to the prostate cancer. As a result, the side effects of the treatment are minimized while the cure rate of the cancer maximized. If you are planning to travel via airline, the radioactive seeds may activate the airport security system. Please request a letter to carry with you when you fly.
What is the difference between preplanned prostate implants and real-time prostate implants?
The majority of physicians performing prostate seed implants in the United States do so using a preplanned procedure. Patients having a preplanned prostate seed implant procedure have a special ultrasound scan performed days to weeks before the actual seed implant is performed. Your Radiation Oncologist and Urologist then determine the areas of the prostate and surrounding structures that need to be treated, as well as those that need to be protected. The Radiation Physicist or Dosimetrist then enters this information into a treatment-planning computer. A plan is formulated that optimizes the seed placement for your prostate.
An order is then placed for the number of seeds needed for your prostate implant, at a precise radioactive strength per seed. The Urologist and Radiation Oncologist then follow the preplan in the operating room and perform the procedure as it was designed. Of course, the situation is often slightly different during the operation than at the time of the preplanning ultrasound study, and your physicians will make the necessary intraoperative modifications.
The other commonly used prostate implant technique is called a real-time prostate implant. Based on the volume of your prostate, a given number of seeds of a given radioactive strength are ordered based on a nomogram (a reference table of sorts). Then the Urologist and Radiation Oncologist determine where the seeds will be placed when the implant is performed in the operating room using data from the ultrasound machine and a powerful, portable computerized treatment planning system. This makes adjustments for gland changes due to positioning or other factors far easier.
Will there be a lot of pain after seed implant therapy?
No, most people are comfortable after the procedure and usually an over-the-counter preparation such as acetaminophen or ibuprofen is all that is necessary to alleviate any discomfort that may occur. Avoid heavy lifting or strenuous activity for the first five days following seed implant.
What sort of urinary side effects can occur after seed implant therapy?
Most of the urinary side effects occur after a prostate seed implant and are a minor problem for the first few months after the seed implant. Other potential problems don’t usually occur until six months or longer after the prostate seed implant. Some of the acute side effects of seed implant therapy are due to the swelling and bleeding within the prostate as a result of the trauma of the needle and seed placement that occurs during the operation. Other acute side effects are due to the radiation injury to the normal body tissues. This swelling narrows the urinary tract and often results in the urinary stream being weak, urinary dribbling, stopping and starting of the urinary stream, having to push or strain to begin urination. The acute side effects of the radiation are manifested primarily as increased urinary urgency and a burning or stinging sensation during urination, similar to that of a bladder or prostate infection. Your physician will likely prescribe a variety of medications to help minimize the discomfort from these symptoms. Sometimes the bladder becomes severely obstructed by the swelling and a Foley catheter must be placed back in the bladder for a few days or, on occasion, a few weeks. If it appears that this will be a problem for a few months, the patient will either be taught to catheterize himself or an indwelling catheter will be placed. The main possible long-term side effects are chronic bladder outlet obstruction, urethral ulceration, and urethral necrosis with resultant pelvic pain; very rarely, urinary incontinence; and, extremely rarely, formation of a track between the rectum and urethra (called a fistula) with leakage of urine from the rectum.
What sort of rectal side effects can occur after seed implant therapy?
In general, very few rectal side effects occur after prostate seed implants. However, sometimes side effects do occur. Some may occur shortly after the implant while others may not occur until many months later. The most common side effects during the first few months after the implant are an increased urgency of bowel movements; slight burning sensation of the rectum during bowel movements (kind of like hemorrhoid type of discomfort); and, rarely, some leakage of brown mucous type material with the passage of rectal gas. The main long-term problem is formation of a painful rectal ulcer if an implant seed is placed too close to the rectal wall or even into the muscle of the rectal wall. Some patients will have rectal bleeding similar to that which occurs after external beam radiotherapy. Extremely rarely, there can be a formation of a track between the rectum and urethra (called a fistula) with leakage of urine from the rectum.
What is the post-implant dosimetric evaluation?
Regardless of which technique your physician uses to perform your implant, you will very likely have an evaluation of your prostate seed implant performed the same day as your implant or within the month following your prostate seed implant. This often involves having certain radiological studies performed.
A CT scan through the prostate region is obtained. This allows your Radiation Oncologist to see the implant seeds, the prostate, and other surrounding organs and structures, as well as the actual location of the seeds within and around the prostate. This information is entered into the 3-D treatment-planning computer and your implant can be carefully evaluated to assure that the desired result was actually achieved.