Zapping prostate tumors

June 04, 1991|By Jonathan Bor

Physicians at the University of Maryland Medical Center are encouraged that a new method of implanting radioactive seeds into prostate tumors can shrink the cancerous growths -- and possibly spare patients from the second leading cancer-killer of all men.

The specialists say they haven't had enough experience with the technique to claim success, but early signs offer hope that radioactive seeds can bring about significant shrinkage without the harmful side effects of "external beam" radiation.

Physicians say it is intended for men over the age of 70 whose cancers have not spread to other parts of the body. Surgical removal of the prostate, regarded as too risky for older men, is still considered the "gold standard" for younger men with cancers that are confined to the prostate or the immediately surrounding tissue, the doctors said.

Here's how the technique works:

Patients stay awake but get total pain relief from epidural anesthesia, which simply blocks all sensation in the pelvic area. Doctors inject 50 to 70 tiny radioactive seeds through the perineum -- directly into the prostate. Ultrasound gives the doctors an inside view, enabling them to distribute the pellets precisely and evenly throughout the gland.

The steel "seeds" are impregnated with a radioactive iodine, which attacks the tumor with a radiation dose that's about four times as strong as the dose delivered by an external beam. Localizing the radiation also appears to spare patients the diarrhea, fatigue and burning sensation with urination that can occur when radiologists attack the tumor with an external beam, which exposes a much wider area.

"With radioactive seeds, we can administer higher doses of radiation directly at the site of the tumor, while not harming surrounding tissue," said Dr. Pradip P. Amin, a radiation oncologist at Maryland. External radiation, however, remains the standard therapy for men whose prostate cancer has spread to the lymph nodes.

The University of Maryland, which began the treatment in August, is one of four centers in the United States using iodine-laced "seeds." Of 11 men treated so far, doctors report, the treatment has brought about at least a 30 percent prostate shrinkage in the first six. It's still too early to determine prostate shrinkage for the other five, who were treated within the last three months, they said.

It will take biopsies to determine if the five men are cancer-free. Dr. Stephen Jacobs, chief of urology, said a 30 percent shrinkage of the entire gland -- only part of which is the tumor itself -- might be enough to eliminate all of the cancer.

In the last two decades, he said, doctors implanted radioactive seeds surgically, which entailed a 6- to 8-inch incision and a one-week hospital stay. But they abandoned the technique because they were unable to distribute the pellets evenly enough to cause significant shrinkage.

The new method allows patients to go home after one night in the hospital because no cutting is done.

Prostate cancer is the second-leading killer of men, trailing lung cancer. But among men 70 years and older, it ranks as the leading cancer killer. The American Cancer Society estimates that 122,000 cases of prostate cancer will be diagnosed in 1991, and 32,000 men will die of the disease.

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