Among prostate cancer patients, death from other causes was somewhat higher in the screened group (10.7 percent of 4,250 men with prostate cancer) compared to the usual care group (9.9 percent of 3,815 men with prostate cancer).
This indicates men who underwent PSA screening were over-diagnosed, meaning the test picked up slow-growing tumors that probably weren't lethal, the researchers said.
"PSA testing and digital rectal examination screening as conducted in this trial did not reduce prostate cancer mortality, but there was a persistent excess of prostate cancer cases in the screened arm, suggesting over-diagnosis of prostate cancer," Prorok said.
Some prostate cancer experts disagree with the authors' conclusions.
Dr. Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston, said the results are invalid because the trial was flawed.
According to D'Amico, 52 percent of those who received usual care had a PSA screening. "That's a serious issue which makes it very hard for the study to show if any benefit exists for PSA screening," he said.
Also, 15 percent of those who were supposed to get PSA screening never did, D'Amico said. "So what you've got is a screening study in which 85 percent of the people got PSA screened on the screening arm and 52 percent got screened on the control arm, which makes it impossible to ever measure a difference," he said.
Men should ignore this study, "because it has no relevance to PSA screening," D'Amico said.
D'Amico said he has more confidence in the results of a European study published in 2009 in the New England Journal of Medicine, which showed a 20 percent reduction in cancer mortality with PSA screening.
Men who can benefit most from screening are those at risk for prostate cancer, particularly men who have a family history of prostate cancer, Afr
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