Screening men more often for prostate cancer uncovers more tumours, but it does not reduce the number of aggressive cancers found, European researchers report.
The study concludes that it doesn't hurt to wait four years between prostate cancer screenings, though the debate on the ideal timing of tests will likely continue.
Dutch and Swedish researchers tracked about 4,000 men in Gothenburg, Sweden, who were given a PSA blood test (prostate-specific antigen) to screen for prostate cancer every two years, and another 13,000 men tested every four years in Rotterdam. They were 55 to 65 years old at the time of the first screening.
Over a 10-year period ending in December 2005, detection of any form of prostate cancer was higher among the Swedish men who were screened more frequently -- 13 per cent -- compared to the Dutch men who were screened less often -- 8 per cent.
But 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. In fact, only a handful of aggressive between-test cancers formed in each group -- a statistical tie, concluded the researchers.
And in an accompanying editorial, Dr. E. David Crawford of the University of Colorado noted that it's possible the Dutch men may have been healthier.
The authors note that larger cancers seem to be identified with equal effectiveness if screening takes place every two or four years.
Millions of men in North America have their blood tested every year for PSA. High PSA levels can mean cancer or just an enlarged prostate; only a biopsy can tell.
Moreover, even when tumours are found, the cancer is usually slow-growing and may not require any treatment. The problem is there's little way to predict which early-stage tumours will threaten life. And since treatment can cause incontinence or impotence, PSA testing may do more harm than good for some men.
