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Yet another study finds little benefit from most prostate cancer screening with PSA

September 13, 2010

Yet another study has questioned the benefit of prostate cancer screening with the prostate-specific antigen (PSA) test, in this case for men who have low PSA values at their initial test. European researchers reported Monday that, for men with the lowest PSA values, repeat testing, biopsies and cancer treatment reduce quality of life but do little to increase survival. They found that among men with PSA levels lower than 2 nanograms per milliliter in their first test (4.0 or lower is usually considered normal), 24,642 men would have to be screened and 724 cases of prostate cancer would have to be treated to save one life. In contrast, for men with first levels between 10 and 19.9 mg/nl, 133 men would need to be screened and 60 treated to prevent one death. The study did not examine men with higher PSA levels because there is general agreement that such men need futher testing.

Prostate cancer is the most common form of cancer -- other than skin cancer -- to be diagnosed in U.S. men and the second leading cause of cancer death, behind only lung cancer, according to the American Cancer Society. About 217,730 men will be diagnosed with the tumors this year, and more than 32,000 will die. A man has about a 15.8% lifetime chance of being diagnosed with prostate cancer but only a 2.8% risk of dying from it. The disparity in the numbers arises not because treatment is highly successful but because the majority of prostate cancers are slow-growing tumors that pose little risk to the man who has them. In fact, autopsy studies show that most elderly men have undiagnosed prostate tumors when they die. The problem is that physicians have no accurate way to differentiate between those tumors that are slow-growing and present little or no risk and those that are aggressive and need treatment. Some groups have advocated that the cutoff PSA value for further screening be lowered to 2.5 mg/nl, but critics charge that this would double the number of men who undergo unnecessary biopsies.

PSA is a protein produced by cells in the prostate gland and is not specifically linked to tumors. It can be  produced by benign prostate hyperplasia and other conditions as well. But it is the only tool clinicians currently have.

Two studies released in March 2009 showed little benefit from PSA screening. An American study of 76,000 men found no benefit from the screening, while a European study of 162,000 men found a 20% reduction in deaths associated with screening, although the results were not statistically significant -- meaning they could well have originated by chance.

In the new study, published online in the journal Cancer, Dr. Pim van Leeuwen of the Erasmus University Medical Centre in Rotterdam, the Netherlands, and his colleagues reexamined data from that European study, looking specifically at 43,987 men ages 55 to 74 who had been screened repeatedly and treated. The researchers compared the men with a similar group in Northern Ireland, where routine PSA screening is not carried out. The team concluded that screening was beneficial for men whose initial PSA level was higher than 10 but not for men with lower values. Proponents of screening, however, said that the follow-up for the men was only about 10 years and that a minimum of 15 years is necessary to show the benefits of screening.

The American Cancer Society and other groups do not recommend routine prostate cancer screening. Instead, they urge physicians to have a frank dicussion with patients about the pros and cons of screening. The groups recommend that screening not be performed in men older than 75 and that repeat screening not be conducted in elderly men with low PSA levels who are expected to live less than 10 years.

Dr. Otis W. Brawley, chief medical officer for the American Cancer Society, said Monday that men who have a low value on an initial screening could probably safely go five or more years before they have an additional PSA test.

-- Thomas H. Maugh II / Los Angeles Times

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