Patient FAQ
What parameters: PSA, Gleason score or other, should a man have in order to be a candidate for seed implantation?
In general, patients with PSA less than 10 and Gleason score of six or less are good candidates for implant alone. Most men will be candidates for seed implantation (S.I.). S.I. is performed either alone or in combination with external beam radiation. The challenge for physicians is deciding which patient needs external beam radiation. We use the Partin tables more often now to help us decide which patients need the combined external beam and implant approach. Patients with a high risk of disease outside the gland generally receive a short course of external beam radiation (5 weeks) prior to seed implantation. Some men will have a large gland, unusual anatomy or TURP defect, which technically prevents a good implant - but this occurs rarely.
What factors do you take into consideration when picking Palladium 103 or Iodine 125 for the implant?
Gleason grade has been, in the past, the primary determinant for picking an isotope. Early open (laparotomy) implant experience with I-125 with moderate grades (2-6) was quite favorable but not so favorable with high-grade tumors (Gleason 8-10). We therefore initially elected to treat patients with low to moderate grades (2-6) with Iodine 125 and higher grades (7-10) with Palladium 103. To date, this has worked out well. For Gleason scores 5-7, either isotope is probably effective. It will require a controlled study and many patients to determine if one isotope is better than the other.
Please describe the volume study and the mapping of the prostate.
The volume study is the first step of the mapping procedure. This is an ultrasound procedure in which images of the prostate are taken at 5mm increments. These images are then reassembled on the computer to make a three dimensional model. Using this model, we can determine the exact placement of each seed. After a careful review by each member of the team (physician, physicist, dosimetrist and nurse), a map of the gland is created which describes the correct coordinates for needle and seed placement. This map is taken into the operating room and followed closely. Additional seeds are available in order to make adjustments at the time of surgery.
Please describe the length of the procedure and the type of anesthesia.
Typically, the procedure takes about an hour and is done under spinal or light general anesthesia. Spinal anesthesia is preferred because patients seem to tolerate it quite well, are more alert immediately after the procedure and recover the feeling in their legs within thirty to sixty minutes. Since patients can be as alert as they wish to be during the procedure, they can watch the procedure on the monitor. General anesthesia is perfectly acceptable, however. Note too, that with a spinal anesthetic, the type and amount of anesthetic agent determines how long it takes for the anesthesia to wear off.
What can the patient expect to feel like the remainder of the day after the procedure?
As with all procedures, patient response is varied. The procedure causes minimal trauma to the region beneath the scrotum, but there can be some tenderness and bruising. Most patients require only minimal pain medications such as Extra Strength Tylenol. After the procedure, most patients are somewhat tired and want to relax. Patients can engage in normal activities (walk around, have dinner, etc.) if they feel up to it.
Why will the patient have a CT scan and chest x-ray soon after the procedure?
The CT scan is done to confirm the placement of the seeds. The CT allows the implant team to do a dose determination called dosimetry. The post-implant dosimetry acts as a permanent record of the implant. It also gives the implant team another means of evaluating the quality of the implant. On very rare occasions, additional therapy may be suggested.
Also on rare occasion, a "free" seed (a seed that is placed in the needle individually) will be inadvertently implanted in the middle of one of the large veins around the prostate. This seed can travel in the veins, eventually reaching the lungs. Seeds in the lung have not caused any harm to any patient, nor resulted in any adverse symptoms. The chest X-ray is performed to determine if there is a seed in the lung.
Will you explain the differences between palladium and iodine seeds?
Iodine and palladium seeds are nearly identical in their appearance. Both are 0.45 cm long (about the size of a grain of rice) and are implanted in the same way. Both emit low-energy radiation. The primary difference between these two isotopes is the rate at which they give off their energy. Palladium gives up 90% of its energy within two months, while it takes approximately six months for iodine to release 90% of its energy. There are advantages to using both isotopes, which are described below in a related question about seed selection. There is no proof that one seed is better or stronger than another. The doses and seed strengths, in fact, are prescribed to produce the same biologic effect.
What dose of radiation will each kind of seed give during its lifetime?
It depends on whether the seed is used as implant alone or in conjunction with external beam.
Implant alone |
Iodine |
145 Gray *(=14,500 cGy or rads) |
Palladium |
115 Gray (=11,500 cGy or rads) |
|
EBRT & implant |
Iodine |
110 Gray *(=10,000 cGy or rads) |
Palladium |
90 Gray (=9,000 cGy or rads) |
Note that this new description for iodine doses (TG 43*) is being adopted by many centers. This is not a change in the energy given or seed strength used, but a means for physicists and physicians to describe more accurately what dose is given. For example, instead of the old prescription dose of 160 Gy, the new prescription will be 145 Gy. Patients should not be worried that they are getting a smaller dose by this new method. It is the same dose used with the older system.
Please explain seed "half life". How long will each kind of seed be radioactive after implantation?
Half-life describes the time in which an isotope loses half of its strength. For example, iodine, which has a half-life of 60 days, will be half of its strength at 60 days. 60 days later it will be half of this strength. It takes about six months for iodine to be at about 10% of its original strength and a year to lose all of it.
Palladium has a half-life of 17 days. Within two months it has given up 90% of its energy and has lost almost all of it by six months. Again, there are advantages to both isotopes. Palladium gives up its energy quicker but this does not mean that it is necessarily better or stronger.
How does radiation from seed implantation affect cancer cells? Are there forms of prostate cancer cells that will not be affected by seed implantation radiation? How will the radiation from seed implantation affect healthy cells in the patient's prostate?
Radiation kills cells primarily by affecting a critical target in the cell. This critical target is believed to be the DNA or RNA elements of the cancer cell, which are important for growth. Cancer cells don't die immediately after radiation. Instead, when the cell tries to divide into two cells, the effect of the radiation on the DNA/RNA prevents the cancer cell from dividing properly and the cell dies Since prostate cancer cells often divide slowly, the cancer cell may not die for months after the implant. This is why it sometimes takes a long time for the PSA to drop to low levels. Since the cancer cells are most sensitive to radiation at the time of division, we like to have some radiation present when this occurs. This is why, for slower growing cancers, Iodine 125 is used. For faster growing (higher-grade) cancers, the division is quicker and therefore it may make sense to use Palladium 103, which gives up its energy more quickly.
All cells are sensitive to radiation. Normal prostate cells die as result of the implant radiation. Some normal cells remain however, which explains why PSA is still present years later. When healthy cells die, the prostate’s ability to produce prostatic fluid for ejaculation may be substantially reduced. The presence or absence of an ejaculate, however, does not reflect whether the cancer is cured or not.
Will healthy cells regrow after the radiation is complete?
There is some regrowth of normal cells, but for the most part regrowth is very slow. This regrowth of normal prostate cells is believed to be responsible for the increase of PSA values in some patients after treatment.
If the patient has BPH (benign prostatic hypertrophy) prior to seeding, will it go away or return later?
No investigator has looked at this issue carefully. While the gland can shrink with the radiation, often patients have urinary function similar to that prior to the implant. In other words, at this point seed implantation does not seem to be a good treatment for BPH.
What are the chances the patient will be affected by prostatitis after seeding?
All patients have some inflammation of the prostate (prostatitis) after seeding which typically resolves as the seeds lose their energy. The presence of prostatitis prior to seeding is always a concern because the prostatitis may be exacerbated by the radiation. Surprisingly, this has not occurred in the patients we have treated. This is not to say that prostatitis symptoms went away after implantation but that the implants did not seem to have significantly worsened them. With these patients we urge caution. This is an area that needs closer study.
What effect would a TURP, either previous to or after seed implantation, have on treatment?
In some patients, the presence of a previous TURP prevents a technically good implant. In the past, patients with a prior TURP have had approximately a 25 percent increased risk of urinary incontinence at six years. The majority of this incontinence was minor, requiring a simple pad. Over the past several years there have been changes made in the pattern of seed placement in these TURP patients with the hope of decreasing this risk. Since it takes some time to learn the results, patients with a prior TURP are advised that their risk of incontinence is higher. There are, of course, often very good alternative treatments (radical prostatectomy or external beam radiation).
TURP after the implant also imparts a risk of incontinence. Therefore, a TURP in implant patients is not generally recommended. When a TURP is necessary after implant, it should be performed by someone who understands the problems associated with it.
What follow up will there be after seed implantation?
The first visit is at 6-8 weeks and thereafter every three months for two years. After two years, visits are recommended every six months. After five years, a PSA is scheduled every six months and a physical exam at least once a year. Alternating these visits between the radiation oncologist and urologist insures complete care. If the patient has a good internist or family practitioner, we encourage his/her participation as well. Most important is to have a concerned, knowledgeable physician following the course.
What are the effects of seed implantation on short and long term potency?
The effect of the implant on potency can be immediate or delayed. Our studies so far have indicated that overall, approximately 25% of men who are fully potent (able to achieve an erection) prior to implantation, will become impotent after. Another 25% will experience some decrease in their ability but still have intercourse. At present, there is no way of predicting who will be affected and when. Many men who are potent will notice a decrease in the durability or firmness.
Can seed implantation cause long or short-term incontinence?
The risk of long term incontinence after either seed implant alone or in combination with external beam radiation in the typical (non-TURP) patient is extremely low: less than 1%. Short term, some patients experience significant urgency and may have difficulty reaching the restroom without some slight dribbling. This resolves as the seeds lose their energy.
Please explain why nighttime is worse than daytime for urine retention and difficulties in urination.
For many men, nighttime urination is a different experience than daytime, with often a slower stream or difficulty initiating a stream. This phenomenon can be worsened after seed implantation or external beam radiation. The reason for this is unclear. It may be worse at night because there is slightly greater swelling of the prostate at night. Alpha blockers (Flomax, Cardura or Hytrin) are prescribed to help minimize this symptom. Often, walking around will alleviate this problem. Generally, this worsening of the urinary stream at night goes away as the seeds lose their energy.
