Men who have undergone surgery to treat earlier stage prostate cancer may not need to keep up yearly PSA tests to screen for a cancer recurrence, a new study suggests.

Instead, researchers say, men who have a low risk of cancer recurrence can safely get less-frequent PSA screening -- every two years, or even less often, in the longer term.

If that idea were widely applied, it would change the long-term follow-up care of a substantial proportion of men treated for prostate cancer.

About 90,000 men undergo radical prostatectomy -- surgical removal of the prostate -- each year in the U.S., and 50 percent to 60 percent of them are considered low risk for cancer recurrence, noted Dr. Matthew K. Tollefson, a urologist at the Mayo Clinic in Rochester, Minnesota, and the lead researcher on the new study.

PSA, or prostate-specific antigen, is a protein produced by the prostate gland, blood levels of which generally rise when a prostate tumor is present. PSA blood tests can catch the cancer in its early stages, or detect early signs of a recurrence in men who have been treated for the disease.

Right now, men who undergo radical prostatectomy typically have a PSA test every few months in the first year after surgery. That may continue in the second year or be extended to six-month intervals, and then to yearly intervals in the longer term.

But that pattern is based largely on data from men treated for prostate cancer with a relatively high risk of recurrence, Tollefson noted in an interview.

In their study, reported in the Journal of Urology, Tollefson and his colleagues found that for men with a low risk of recurrence, long-term yearly testing appeared unnecessary.

The study included 2,219 men who underwent radical prostatectomy at the Mayo Clinic between 1994 and 2004. In the year following surgery, the men underwent PSA screening every three months; the interval was extended to every six months in the second year, and then yearly thereafter.

During the study period, 142 men, or 6 percent of the study group, had a so-called biochemical failure -- a rise in PSA that can serve as an early indicator of recurrence, though it does not necessarily mean the cancer is back.

The researchers found that the longer a man went with undetectable PSA levels, the lower the odds of having a biochemical failure.

Overall, 2,193 men -- the large majority of the study group -- had undetectable PSA levels one year after surgery. Of those men, just under 4 percent ultimately had a biochemical failure; that compared with just under 3 percent of patients who were still PSA-free two years after surgery.

The likelihood decreased to just over 1 percent among men who had undetectable PSA at the four- and five-year marks.

What's more, the study found, the chances of having a biochemical failure one year after an undetectable PSA result were quite low.

After one year of undetectable PSAs, only 0.1 percent of men had a biochemical failure in the next year.

Low-risk men probably don't need to be screened as often as they are, Tollefson said.

For men who have undetectable levels after the first post-surgery year, a PSA test every two, three or even four years may be enough, according to Tollefson. And once a man has been PSA-free for five years, he and his doctor might consider stopping screening altogether.

All of the patients in the study were considered low-risk because, among other factors, they had been treated for earlier stage cancer still confined to the prostate and their tumors did not have abnormalities that suggested an aggressive form of the disease.

A limitation of the study is that all of the patients were treated at a single medical center, rather than a sampling of U.S. hospitals. However, the researchers think the findings can be widely instructive in the post-surgical follow-up of men with low-risk cancer.

The findings would not apply to men with more extensive or aggressive cancers at higher risk of recurrence, according to Tollefson.

Men at low risk might wonder what harm there could be in doing yearly PSA testing over the long term. But Tollefson pointed out that the testing process can be anxiety-provoking, as well as costly.

A single PSA test ranges from $70 to $400, and along with the cost of the physical exam and seeing a specialist, the price tag can be significant. Extrapolated to the entire population of U.S. men who have been treated for low-risk prostate cancer, those costs quickly add up, Tollefson noted.

He suggested that these patients talk with their doctors about how often they need PSA testing and whether, over time, less-frequent screening could be right for them.

I think these findings suggest that patients at low risk for progression can relax, Tollefson said. It's reassuring to see that the risk (of recurrence) is low.

SOURCE: Journal of Urology, September 2010.