Gleason scores of the highest grades “ “8 or 9 “ “were found in only seven participants, or 0.2 percent of men in the PCPT control arm. Most of the men with prostate cancer, 349 of them (78 percent), had Gleason scores of 5 or 6.

"Most of these men would not have been diagnosed if they had not taken part in this study, since biopsies are not routinely performed in men with such low PSA levels," said Ford.

"We need better methods to distinguish the harmless, slow-growing cancers from the more aggressive ones," continued Ford. "If more biopsies are performed at lower PSA levels, more cancers will be found and treated. But some men would undergo treatment, and the risks associated with it, for tumors that would never have been clinically significant."

Treatment for prostate cancer can sometimes lead to impotence, urinary incontinence, and other problems, causing a substantial health burden for men.

"Lowering the PSA threshold for proceeding to prostate biopsy would increase the risks of overdiagnosing and overtreating clinically unimportant disease," said Thompson.

NCI-funded researchers are looking for ways to determine which men harbor aggressive tumors. The NCI Early Detection Research Network (EDRN) has a Prostate Collaborative Group, which is applying a variety of strategies to find ways to detect prostate cancer early. Some scientists are using the new tools of genomics and proteomics to look at how gene expression patterns and proteins in the blood may differ in men with aggressive tumors vs. those with slow-growing ones.

"There is a great need for methods, beyond tumor grade, to better predict which men have prostate cancers requiring treatment," said Thompson.

Prostate cancer is the most common cancer in men, after skin cancer. It estimated that approximately 230,110 men in the United States will be diagnosed with the disease this year, and about 30,000 men will die from it.

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