Permanent Seed Implants (LDR)

This type of seed implant is referred to as low dose rate or LDR because it treats the prostate over a long period of time. Pellets of radioactive material (iodine-125 or palladium-103 isotopes) are placed into thin needles, which are inserted through the perineum (area between the scrotum and anus) into the prostate. The pellets (seeds) remain in the place as the needles are removed and continually give off low doses of radiation for weeks or months as prescribed. An average of 80 seeds are positioned.

Because the seeds are so close to the cancer cells, the cells are inundated with radiation while the rectum, bladder and other healthy tissues receive much less. Due to the seeds small size, their presence is essentially unnoticed. The seeds remain in place after their radioactive substance has been depleted.

The Implant Process

The patient first undergoes a four to five week course of daily IMRT. This external beam therapy provides a dose of radiation to areas around the prostate that are beyond the reach of the radiation that will be emitted by the seeds alone. The seed implant is performed during the four-week period following the final IMRT treatment.

Implantation is normally done on an outpatient basis in the operating room under general or spinal anesthesia. The physician is guided by ultrasound for the most accurate placement of each seed in order to maximize exposure to the cancer cells and minimize the effect on surrounding tissues and structures.

Choosing Permanent Seed Implants

Permanent seed implants have been used for many years in treatment and cure of prostate cancer. Only one outpatient implant procedure is required. Long-term studies show that permanent seeds are highly effective and have essentially the same results as surgical removal of the prostate (prostatectomy).

Men who choose this procedure will be advised that they will give off small amounts of radiation. The radiation doesn’t travel far, but the patient is cautioned to avoid pregnant women and take precautions with small children under eighteen months of age for the first couple of months after implant. There is also a small risk that some of the seeds may migrate to other parts of the body such as the lungs, although, such migration is not normally associated with any ill effects.

Are All Seeds the Same?

The mean number of patients treated with Palladium returned to normal American Urological Association (AUA) symptom score of 7, four months sooner than patients treated with Iodine.

Although Iodine is the most commonly used isotope, Gulf Coast Cancer Treatment Center uses both seed options. The choice of type is determined relative to the individual patient’s disease characteristics and radiobiologic considerations.

Next: Permanent Implant Before or After Radiation?