New Delhi, April 6 (IANS) A simple blood test that checks for prostate-specific antigen (PSA), a marker for prostate cancer, is safe and sufficient, if done at intervals of every five years, finds a study on Saturday.

Screening for prostate cancer has historically been a controversial subject. While the PSA test has been effective in screening the risk, it is also known for false positives leading to unnecessary invasive treatments and false negatives leading to cancers being missed.

"This is gradually changing due to MRI scans which can avoid unnecessary biopsies and the use of 'active surveillance', where men with early-stage cancer are monitored and only undergo treatment if their disease progresses," said the researchers from Heinrich-Heine University, Dusseldorf in Germany.

The team's study, presented at the ongoing European Association of Urology (EAU) Congress in Paris, France, showed that five years is enough to screen low-risk men for prostate.

They noted that the "screening interval for those at low risk could be much longer with minimal additional risk".

The findings come as a new analysis published in the Lancet Commission on Friday showed that cases of prostate cancer are likely to double worldwide to 2.9 million per year, while annual deaths are projected to rise by 85 per cent -- to almost 700,000 deaths by 2040.

The new study included men aged 45 split into three groups. Men with a PSA level of under 1.5 nanograms per millilitre (ng/ml) were deemed low risk and followed up with a second test after five years.

While those with a PSA level between 1.5-3 ng/ml were deemed intermediate risk and followed up in two years, men with a PSA level over 3 ng/ml were found in the high-risk category and given an MRI scan and biopsy.

Of over 20,000 men recruited to the trial and deemed low risk, 12,517 have now had their second PSA test at age 50.

The results, also forthcoming in the journal European Urology, showed that only 1.2 percent of these (146 in total) had high levels of PSA (over 3 ng/ml) and were referred for an MRI and biopsy. Only 16 of these men were subsequently found to have cancer -- just 0.13 per cent of the total cohort.

"By raising the bar for low risk from 1 ng/ml to 1.5, we enabled 20 per cent more men within our cohort to have a longer gap between tests, and very few contracted cancer in that time," said lead researcher Professor Peter Albers, from the Department of Urology at the University.

"Our study is still underway, and we may find that an even longer screening interval, of seven, eight, or even ten years, is possible without additional risk," he added.