Prostate Cancer Treatment Using Radioactive Seeds Implanted in the Prostate Gland
In brachytherapy, another type of radiation treatment for prostate cancer, 80 to 120 radioactive seeds (tiny metal pellets) are implanted directly into the prostate under ultrasound guidance. For several months, they emit a highly concentrated radiation dose. The pellets remain harmlessly in the body after their radioactive energy is spent.
Brachytherapy is appropriate for men with early-stage prostate cancer (stage T1) who have a Gleason score of 6 or less and a PSA level of less than 10 ng/mL. But the procedure does not appear to be as effective as radical prostatectomy or external beam radiation therapy for men with higher-grade tumors or more advanced stages of disease.
Consequently, an expert panel recently recommended against using brachytherapy in men with stage T2 or higher cancers, Gleason scores of 7 or more, or PSA levels above 10 ng/mL. The same panel also recommended against combining brachytherapy with external beam radiation therapy because of a higher risk of side effects. However, this approach is advocated by those who believe that the combination of brachytherapy and external beam radiotherapy improves the chances for a cure.
The side effects of brachytherapy are similar to those of external beam radiation therapyurinary and bowel problemsbut these complications may occur more often with brachytherapy. Men with bothersome lower urinary tract symptoms are more likely to have worsening of these symptoms after brachytherapy when compared with other treatments.
In addition, the radioactive seeds can migrate to other parts of the body, such as the lungs, although research suggests that seed migration has no negative consequences. Because brachytherapy alone could be associated with a lower chance of a cure and a somewhat higher rate of complications than external beam radiation therapy, external beam is still considered the gold standard of radiation treatment for prostate cancer.
Two refinements of brachytherapy are MRI-guided brachytherapy and high-dose-rate brachytherapy. The potential advantage of MRI-guided brachytherapy is a more precise placement of the radioactive pellets than what can be achieved with ultrasound guidance. In high-dose-rate brachytherapy, radioactive pellets are delivered to the prostate via 25 hollow plastic needles. Over a 24- to 48-hour period, radioactive pellets are placed in the needles and then removed.
Available research suggests that outcomes are similar among men treated with high-dose-rate brachytherapy or traditional brachytherapy. However, men treated with the newer technique experienced fewer side effects, including less urinary frequency, incontinence, blood in the urine, and rectal pain.
Increasingly, men with early-stage prostate cancer are opting for short-term use of hormone therapy in combination with radiation therapy. Hormone therapy is sometimes given to men with larger prostates (greater than 40 g, or about 1.5 oz) who are scheduled to start brachytherapy. The aim is to shrink the prostate before the radioactive pellets are implanted. However, no well-designed randomized clinical trial has yet shown a survival benefit for this approach. The general consensus is that men with higher-stage cancers (stage T2 or above), higher-grade cancers (Gleason score of 7 or more), or PSA levels of 10 ng/mL or more have better outcomes when radiation therapy is accompanied by hormone therapy.