The latest research has done little to settle the debate over the effectiveness of frequent screening for prostate cancer.
The controversy over the value of screening tests for this common cancer in men and how frequently they should be performed continues to rumble on.
European researchers have conducted a study where men were tracked who were given a prostate-specific antigen (PSA) blood test for prostate cancer; 4,000 men in Gothenburg, Sweden were given the test every two years and 13,000 men were tested every four years in Rotterdam.
The men were 55 to 65 years old at the time of the first screening.
The Dutch and Swedish researchers say as expected more tumours were found in the two year test group but that still failed to reduce the number of aggressive tumours detected in between scheduled screenings.
The researchers found over a 10-year period ending in December 2005, the detection of any form of prostate cancer was higher among the Swedish men who were screened more frequently- 13 percent - compared to the Dutch men who were screened less often - 8 percent.
However in the long term there was no statistically significant difference in the two groups in the number of aggressive tumours that appeared between the times when the tests were conducted.
The researchers say this demonstrates that more frequent screening does not cut the number of cancer cases as might have been expected.
Study leader Monique Roobol of Erasmus Medical Centre in Rotterdam says how frequently men should be screened for prostate cancer remains a tricky question.
The researchers suggest that each PSA test may lead to prostate cancer diagnoses among some men who may have a "clinically insignificant form of the disease" and over-diagnosis and over-treatment should be avoided.
The American Cancer Society says diagnoses of prostate cancer have risen substantially since screening using PSA tests began in the late 1980s but while the death rate has dropped, it remains unclear whether this is a direct result of the screening.
The American Cancer Society recommends that both the PSA and DRE should be offered annually, beginning at age 50, to men who have at least a 10-year life expectancy. Men at high risk, such as African American men and men with a strong family history of one or more first-degree relatives diagnosed at an early age, should begin testing at age 45.
The screening detects tumours in their early stages when they are easiest to treat, but it often reveals minor tumours which may pose no threat but receive unnecessarily aggressive treatment.
In Europe most institutions assessing prostate cancer give the tests to men every four years.
The World Health Organization said the results of studies already underway into the effectiveness of prostate cancer screening are needed before making any recommendation.
The prostate is a walnut-sized gland that makes fluid for semen and PSA is a substance produced by the prostate.
The findings are published in the Journal of the National Cancer Institute.