Recent Studies Raise Questions About Effectiveness Of Radioactive Seed Implantation
After a decade of being abandoned, the implantation of radioactive seeds for prostate cancer has become popular again and is being marketed aggressively in many places.
Implantation of radioactive seeds was first popularized in the 1970s, but the long-term results were unsatisfactory, at least in part because the seeds could not be accurately placed by hand in the prostate gland. Consequently, “seeds” were largely abandoned until the late 1980s, when ultrasound guidance for seed placement was developed.
Now, two recent reports in medical journals have raised other questions about the effectiveness of seeds as compared with radical prostatectomy or external beam radiotherapy.
One report is from the Pacific Northwest Cancer Foundation in Seattle, Washington, where ultrasound-guided seed therapy was popularized. In the publication, Cancer, Dr. Haakon Ragde and his associates presented 10-year follow-up results in two groups of patients:
A low-risk group with low PSA, low Gleason grade, and low tumor stage who were treated with seeds alone and a high-risk group with higher PSA, higher Gleason grade and higher tumor stage who were treated with seeds plus supplemental external beam radiotherapy.
The results showed that in the low-risk group, the percentage of men who remained free from tumor recurrence (measured by their PSA remaining at less than .5) decreased by 19 percent.
At 7 years of follow-up, 79 percent of the men remained free from tumor recurrence. At 10 years of follow-up, 60 percent of the men were tumor free. The tumor recurrence rate is the same as that achieved with the old hand-held techniques of seed implantation in the 1970s.
Surprisingly, the tumor recurrence rate was higher in the low-risk patients who received seeds alone than in the high-risk patients who received both seeds and external beam radiotherapy. This finding suggests that, even with ultrasound guidance, seed implantation alone was not very effective.
In another report in the Journal of the American Medical Association from the Joint Center for Radiation Therapy at Harvard Medical School and the University of Pennsylvania, Dr. Anthony V. D’Amico compared the results of treatment with seeds, external beam radiotherapy, and radical prostatectomy at 5 years of follow-up.
For patients with low-grade tumors (Gleason 2-4), there was no appreciable difference between the groups in tumor recurrence rate after 5 years. However, for men with moderately (Gleason 5-7) or poorly-differentiated (Gleason 8-10) tumors, patients treated with seeds had a higher tumor recurrence rate than those treated with either radical prostatectomy or external beam radiotherapy.
Taken together, these studies suggest that, in the long term, seeds alone may not be adequate treatment for many patients with early-stage prostate cancer.