About Seed Implantation

Key Considerations

Safety

Many patients inquire regarding radiation safety. The seeds emit low-energy radiation that is absorbed within a very short distance from the seed. For this reason, only a very small dose would be detectable outside a patient. However, in order to follow the principle of as-low-as-possible radiation exposure, we do recommend that patients refrain from prolonged contact with children (such as holding an infant on one’s lap for a long time) or contact with pregnant woman. The metal of the seeds is not enough to setup an airport metal detector. However, since 2001 many airports have installed radiation detectors for obvious reasons. We provide patients with a card indicating the procedure and information regarding the radiation used.

Side effects

Short-term side effects are generally quite limited and include more frequent urination, urinary urgency, slower stream of urine, and some minor skin bruising. Acute urinary retention is rare but possible. For more details please download our handout ‘What to Expect from a Seed Implant’.

Long-term complications are rare with this technique. Impotence, incontinence, and rectal injury are possible with any form of prostate cancer treatment.  Probabilities of any complication will vary from one patient to another based on their particular case.

Regarding impotence, the American Cancer Society estimates, based on age, that 10-30% of men become impotent as a result of seed implantation compared to 40-50% with external beam radiation and 65-90% with standard radical surgery. The ACS reports that nerve sparing prostatectomy results in an impotency rate of 25-30% for men  < 60 and 70% for those over 70.

At SPI, our experience has largely mirrored the ACS, with the following results:

• Men less than 60 - 10%
• Men 60-70 yrs - 15%
• Men older than 70 - 25%

It is important to recognize that pre-implantation sexual function has a large impact on ones chance of maintaining sexual function following radiation therapy.

Incontinence requiring pads to be worn is rare, seen in approximately 1% of patients. When incontinence does occur, it often is ‘stress incontinence’, in which there is leakage when a man coughs, sneezes, laughs, etc. This is caused by radiation damage to the bladder sphincter, the valve that constricts to keep urine from leaving the bladder. Rectal complications include painless rectal bleeding in 2% of patients, which increases to 6% with the addition of external beam radiation. This occurs anywhere from 6 to 18 months after treatment. About two in one hundred patients may have more serious rectal problems, which except in the most rare case can be treated effectively.

PSA Response after Brachytherapy

With surgery, the PSA is expected to go to zero shortly after the procedure as the prostate is removed. In contrast, cancer cells are not killed immediately with radiation. Radiation causes DNA damage and prevents cells from dividing and growing. Often, the cell does not actually die until it attempts to divide, which for prostate cancer can be a significant time. In biologic terms the cells are considered ‘functionally dead’, because without the ability to divide, they are unable to cause any dysfunction or to spread. With radiation, PSA levels will reach their lowest point (the ‘nadir’) anywhere from 1 – 4 years after treatment. Some of the normal, noncancerous, prostate gland will still produce a small amount of PSA as well, since the gland is still present. The PSA values can ‘bounce’, and this should not be a cause for alarm and in fact is very often seen in successful cases.

The previous definition of failure after radiation from prostate cancer, by the American Society of Radiation Oncology, required 3 rises in PSA before declaring failure. The newer definition is that failure (or recurrence) is defined as a PSA increase of 2 ng/dl over the lowest value (the nadir). For example, if the lowest PSA was 0.3, then values bouncing around this are acceptable but if the PSA becomes 2.3 this is considered clinical failure.

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