'The clinical members of our study team feel that these findings are confirming what they had believed all along; we were a bit more surprised,' said a public health epidemiologist. 'A 35 percent difference is quite a large amount.'

This type of early blood testing has been "quite controversial. There are many arguments both for and against the efficacy of this form of early screening," Vivek Goel, one of the study's senior authors and professor of public health sciences and health policy management and evaluation, said in a prepared statement.

Reporting in the August issue of the Journal of Urology, the research team pored over medical records, comparing the PSA testing histories of 236 men with advanced metastatic prostate cancer with those of 462 randomly selected control patients.

They found early PSA testing associated with a more than one-third decline (35 percent) in metastatic prostate cancer risk.

'Fairly Significant Benefit'

"Our study shows a fairly significant benefit, and this benefit is demonstrated even among men who were not screened regularly as part of a screening program. There may be greater benefit from an organized screening program," Goel said.

Goel and fellow researcher Jacek Kopec, both public health epidemiologists, said they were surprised by the level of protective effect provided by early PSA screening.

Public Health Perspective

"What usually happens with tests like these is that clinicians tend to be very supportive while public health people tend to be more cautious," Kopec said in a prepared statement.

"The clinical members of our study team feel that these findings are confirming what they had believed all along; we were a bit more surprised," he said. "A 35 percent difference is quite a large amount so from our perspective it is quite a significant link in the chain supporting that early prostate screening has a positive effect."

More information: The US National Cancer Institute has more about prostate cancer screening.