VOA常速英语:Studies Question Benefit from Prostate Cancer Test

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U.S. and European researchers say the leading test used to screen for prostate cancer may do more harm than good. The new studies are re-igniting debate over the aggressive treatments associated with prostate cancer.

For 20 years doctors have used the prostate-specific antigen test, better known as PSA, to screen for cancer in the walnut-sized prostate gland in the male reproductive system. But controversy has surrounded the test and some doctors say it has led to overdiagnosis and overtreatment of prostate cancer, one of the most common types of cancer in men in the Western world.

In two interim studies to be published next week in the prominent New England Journal of Medicine, U.S. and European researchers found little to no benefit in PSA screening.

In a discussion on the journal's Web site, Dr. Philip Kantoff of Harvard Medical School, says there can be a downside to early treatment in a slow developing disease.

"When you use PSA, you diagnose prostate cancer, and the benefits of diagnosing that prostate cancer, generally, in its early form, are not seen for probably 10 to 15 years," he explained. "Yet the downside effects of PSA screening are immediate if a patient undergoes treatment."

According to Dr. Mary McNaughton-Collins, a researcher at Massachusetts General Hospital and Harvard Medical School, aggressive treatments can lead to side effects such as impotence, incontinence and even early death. She says the problem lies in not having the scientific advances to differentiate between tumors that do not need to be treated from the aggressive cancer that does.

"I think the onus is on us, to maintain that healthy skepticism about a screening program that's built on inconclusive data on whether or not we are helping more men than we're hurting," she said.

Kantoff agrees, saying much of the controversy would diminish if more doctors would separate detection from treatment. Prostate cancer is slow growing and if properly monitored, Kantoff says, for many patients it can be left alone.

Dr. McNaughton-Collins says physicians need to acknowledge the controversy and fully inform their patients of the tradeoffs. 

"For men in my own practice, for some men the PSA decision is the right one," she said. "For many of my men, once they're fully informed, they decide to forgo the PSA test. And for those men, that is the right decision."

McNaughton-Collins points out that the U.S Preventive Services Task Force, which makes recommendations about health care screenings, concluded that the evidence is insufficient to determine whether there are more pros than cons to prostate cancer screening in men younger than 75. They have, however, discouraged screening for men 75 years or older.

She says physicians need to consider their patient's preferences and make it a shared decision-making process on whether to forgo the test.