Earlier Start, Stop for PSA Testing?
Prostate Cancer Screening May Start Earlier -- and Stop Sooner
Early PSA Test -- and Then No More? continued...
In their view, prostate cancer doesn't happen overnight. Instead, Lilja and colleagues see it as a process that begins many years before cancer is diagnosed. And a rise in PSA may signal that this process is under way.
"Our findings are highly important in that they identify this sort of marker signal exists before age 40," Lilja tells WebMD. "It is unique that we have a biomarker with such extensive delay between when a blood sample is drawn and a diagnosis -- and are able to associate this marker with disease."
Lilja and colleagues took advantage of a "natural experiment" -- 21,277 Swedish men aged 33 to 50 who gave blood from 1974 to 1986 as part of a heart study. PSA screening isn't widespread in Sweden, but cancer registries are. So the researchers were able to tell which men got prostate cancer and which didn't.
In their first look at the data, the researchers found that a single PSA test before age 50 predicted low or high risk of prostate cancer. Now they report that a single PSA test before age 40 predicts prostate cancer risk.
"We are seeing that low PSA values are associated with low future risk of prostate cancer," Lilja says. "The median PSA level in this population of men with low long-term risk is around 0.6 ng/mL."
The researchers hoped to find a time point when the prostate cancer process starts. But that effort has not yet been successful.
"So far we have not been able to see an age where we don't see the signal," Lilja says. "But now we know we can identify individuals who, in the future, are quite unlikely to benefit from further testing and intervention. What that means for PSA screening guidelines is not yet known. And how often a low-risk man will need PSA testing, we don't know."
However, AUA spokesman Ira D. Sharlip, MD, clinical professor of urology at the University of California, San Francisco, says the AUA committee responsible for these guidelines is taking a hard look at the Lilja team's data. Current AUA recommendations call for men to start PSA screening at age 50 if they are not at high risk, because relatively few such men get prostate cancer before then.
"The PSA guideline document that AUA has was written in 2000; it is being updated now," Sharlip tells WebMD. "On the basis of this study, there is a possibility they might revise it to age 40."