Brachytherapy Seed Implants
Brachytherapy for Prostate Cancer
External radiation or radioactive seed implants (brachytherapy) are two treatment options that appear to have similar results when used in early-stage patients. Radiation also produces side effects, including impotence, in about half of patients. It can be applied through an external beam that directs the dose to the prostate from outside the body. The FDA also has approved low-dose radioactive "seeds," each about the size of a grain of rice, that are implanted within the prostate to kill cancer cells locally. Called brachytherapy, the seeding technique is sometimes combined with external-beam radiation for a "one-two punch."
The Prostate Implant Program is a multidisciplinary program that includes urology, radiation oncology, radiation safety and radiology. The program offers patients an alternative treatment for early-stage prostate cancer in which radioactive seeds are placed directly into the prostate gland. Current research projects include intraoperative MRI image fusion, real-time intraoperative dosimetry using fluoroscopic and ultrasound imaging, virtual reality guided implants and CT ultrasound implants.
Interstitial radiotherapy ("radioactive seeds")
In the 1970s, the use of permanently placed radioactive iodine implants produced initial results as good as other available radiotherapy techniques and posed a small risk of impotence and other side effects when compared with conventional external-beam radio-therapy and radical prostatectomy.
However, the technique used (freehand placement during laparotomy) was found to distribute the radioactive seeds unevenly throughout the gland and, thus, cold regions may have contributed to the relatively poor outcome.
The use of ultrasound to guide seed placement has corrected the problem of poor seed placement. Also, radioactive palladium seeds have been developed to increase the dose rate. (Palladium has a shorter half-life than iodine.) Currently, both iodine and palladium implants are used, sometimes in conjunction with external-beam therapy.
Long-term results with improved implant techniques are becoming available and early results are encouraging for a select population. Recently, a large multi-institution trial compared the results of radical prostatectomy, radiation therapy, and interstitial radiotherapy in men with low-, intermediate-, and high-risk prostate cancer.
Interstitial radiotherapy, when used as the sole treatment, was equivalent to the two traditional modalities in terms of PSA recurrence rates for low-risk patients. However, the recurrence rates were significantly higher with interstitial treatment in those men with intermediate- and high-risk cancers; specifically, men with a Gleason score equal to or greater than 7 or a PSA greater than 10 ng/cc. Thus, patients at intermediate or high-risk are generally treated with a combination of interstitial treatment and five weeks of external radiotherapy.