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Researchers open several new fronts on prostate cancer

June 14, 2004|Thomas H. Maugh II | Times Staff Writer

Researchers are making their first strides toward treating advanced prostate cancer, a form of the disease that has resisted most efforts to tame it. Several drugs are or soon will be available to prolong survival and improve the quality of life of men whose disease is now considered terminal.

One of the most promising medications, docetaxel, is widely used for treating breast cancer. Two independent studies presented last week at a New Orleans meeting of the American Society of Clinical Oncology showed that the medication can extend the lives of men with late-stage prostate cancer that can no longer be treated with hormone therapies. Physicians have little they can do for such patients.

The two trials enrolled nearly 1,800 men and showed that docetaxel -- trade-named Taxotere -- reduced cancer pain and extended survival by about two months, from 16 to 18 months.

"Two months may not sound like much time to most people," said Dr. Mario A. Eisenberger of the Kimmel Cancer Center at Johns Hopkins University, who co-chaired one of the studies, "but the study shows that prostate cancer responds to docetaxel, and this opens up the door to exploring more options," such as treating patients at an earlier stage of disease.

"A survival benefit with a chemotherapy drug has never been previously shown" for such advanced patients, he added.

The clinical oncology meeting is the largest gathering of cancer researchers each year and addresses a wide variety of tumors, but some of the most interesting findings this year were directed at prostate cancer.

Another team at the Kimmel center presented promising results with a different drug, one that targets biochemical pathways specific to cancer. Such drugs are less likely than conventional chemotherapy to produce severe side effects.

The experimental drug, called atrasentan, blocks the receptor for a protein called endothelin, which promotes the proliferation of prostate cancer cells and stimulates the growth of bone cells at sites where the prostate cancer has metastasized.

Dr. Michael Carducci of the Kimmel center reported on a three-year study of more than 1,000 men with advanced hormone-resistant prostate cancer. The study found that atrasentan reduced the painful progression of metastases to bones by 20%.

Atrasentan "delays the development of pain while maintaining quality of life," he said.

In another study, researchers found that estrogen, a hormone typically given to women to relieve symptoms of menopause, may help prostate cancer patients as well.

Oncologists typically block the production of testosterone, which can fuel cancer growth, in such patients, leading to memory loss, depression and confusion.

Dr. Tomasz M. Beer and his colleagues at the Oregon Health and Science University's Oregon Cancer Center reported that treating the men with estrogen can minimize these symptoms.

Beer and his colleagues studied 19 men undergoing hormone deprivation therapy, assessing a variety of measures of mental status before having the men wear six 7.6-milligram estrogen patches per week.

After a month of treatment, the Oregon researchers found that the men's verbal memory -- but not their working memory -- had improved, that their depression had eased and that they were less confused.

And finally, two studies suggested that a family of cholesterol-lowering drugs called statins may actually prevent the development of prostate cancer, as well as certain other tumors.

The studies were retrospective ones in which men were asked if they had taken the drugs, so researchers are not yet recommending that people should begin taking the drugs for prevention of cancer. But if the results are confirmed in controlled trials, the drugs should provide a major new way to prevent malignancies.

Dr. Jackilen Shannon of the Oregon Cancer Center examined the records of 430 patients at the Portland Veterans Affairs Medical Center and found that men who had taken any amount of statins during the previous five years had a 58% lower risk of prostate cancer than those who had taken none.

Separately, Dr. Stephen Gruber of the University of Michigan and his colleagues reported on a study of 1,708 Israelis with colon cancer and 1,737 who did not have it. They found that people who had taken statins for five years had a 50% reduction in the risk of developing colon cancer.

Previous studies had also indicated that statins reduce the risk of breast cancer.

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