The rate that PSA levels change over time - known as PSA velocity - has always been one of the tests that doctors have used to determine if a man is developing the cancer.
But, say researchers from Memorial Sloan-Kettering Cancer Centre, PSA velocity is a poor predictor of the disease. As a result, many men have gone through unnecessary worry - and further tests and biopsies.
PSA tests have been discredited as they detect a very high level of false-positives - seeing a cancer that isn't there - although doctors have still relied on PSA velocity as a reliable diagnostic measure.
However, this is as unreliable as the basic PSA test. A man whose PSA levels have risen should not worry unnecessarily, say the researchers, and certainly shouldn't rush to have a biopsy. Only those whose PSA levels are very high should seek out further tests.
(Source: Journal of the National Cancer Institute, 2011; February 24: doi: 10.1093/jnci/djr028).