Cancer Research UK scientists have shown that screening for prostate cancer using prostate specific antigen (PSA) would lead to a substantial number of tumours diagnosed at an earlier and more treatable stage.
However, there would be likely cases of overdiagnosed prostate cancer according to a study published in the British Journal of Cancer today.
The researchers studied 43,842 healthy men given PSA testing as part of the ProtecT** study to calculate the number of advanced stage prostate cancers picked up as a result of the testing. They also worked out the length of time during which prostate tumours do not produce symptoms but are detectable by a screening test - the mean sojourn time (MST). The MST test is a method of calculating 'overdiagnosis' and was used to estimate the probability of a diagnosis of prostate cancer which would not have caused symptoms during the patient's lifetime if screening had not taken place.
Some 1,544 men aged 50-69 were diagnosed with prostate cancer through the PSA testing. Overdiagnosis was estimated at one in 10 in the 50-59 age group and increased to three in 10, (31 per cent) in the 60-69 age group.
However, after adjusting for overdiagnosis, two-yearly PSA testing might still result in a reduction in advanced stage prostate cancer of up to 54 per cent.
Study author, Dr Nora Pashayan, a Cancer Research UK scientist at the University of Cambridge, said: "Our results indicate a benefit of screening to reduce the risk of advanced stage prostate cancer. However, this is limited by overdiagnosis. Any screening strategy should take account of the potential benefits and harms of screening. A valuable target for future research would be to estimate the benefit of screening at different ages."
Prostate cancer can be slow-growing or aggressive. Men with a non-aggressive form may not develop symptoms for many years and not always need treatment - the side effects of which can be significant. But the difficulty is that on diagnosis, doctors can not always tell which forms of prostate cancer are aggressive and which are slow-growing.
Lead author Professor David Neal, based at Cancer Research UK's Cambridge Research Institute, said: "Overdiagnosis is a real concern. There is currently no way to tell whether a prostate cancer is aggressive, or passive.
"Until a test has been developed to distinguish between these, we would prefer to avoid treating patients who don't need treatment - because it can lead to unnecessary side effects like impotence and incontinence. It is important that men in their 50s and 60s feel able to talk to their doctors and request a PSA test if necessary."