Three times as many men would end up with advanced prostate cancer if a controversial blood test widely criticised for unreliable diagnoses did not exist, a study suggests.
The prostate-specific antigen (PSA) test is commonly used in Britain and other countries to identify men at risk of prostate cancer. But critics argue that it frequently results in aggressive treatments which carry a risk of serious side-effects, even though the cancer may be benign and harmless.
Concerns about the accuracy of the PSA test have led to it being used on a case-by-case basis, usually involving men who have already complained of symptoms, rather than as a general screening.
The study, published in the online journal Cancer, analysed the incidence of advanced prostate cancer in the early 1980s, before the PSA test was introduced. It found that the test has resulted in a significant improvement in the early detection of cancers that would otherwise spread to other parts of the body.
The scientists said that doing away with the PSA test would likely result in three times as many men than at present developing an advanced stage of the disease, which spreads beyond the prostate gland before being diagnosed.
The study estimated that about 17,000 American men each year are being saved from progressing to advanced prostate cancer by the early detection of their disease with the help of the PSA test.
“Not doing the PSA test will result in many men presenting with far more advanced prostate cancer. And almost all men with metastasis at diagnosis will die from prostate cancer,” said Edward Messing of the University of Rochester Medical Centre in New York, a co-author of the study.
The test measures the amount of a protein called prostate-specific antigen in the bloodstream. Prostate cancer cells and normal prostate cells both produce the antigen, which varies in concentration between individuals and age groups, factors which make a definitive diagnosis difficult.
Prostate cancer is newly diagnosed in 41,000 British men each year and kills more than 10,000 patients annually. It is the fourth most common cancer in the UK and the most common in men, accounting for a quarter of all new cases of male cancers.
The incidence of prostate cancer has increased significantly in recent years, helped by better diagnosis and reporting, partly as a result of using the PSA blood test.
Medical authorities in both the US and Britain have advised against using the PSA test for general population screening because they say it would lead to unnecessary treatment of non-aggressive forms of the cancer in men who as a result would be at risk of side-effects, such as incontinence or erectile dysfunction.
Owen Sharp, chief executive of the charity Prostate Cancer UK, said: “Although recent research does suggest that screening for prostate cancer may reduce the number of deaths from this disease, we still believe that the potential negative impact of screening outweighs its potential positives. As screening can potentially lead to over-diagnosis and unnecessary treatment we do not currently support the introduction of a national screening programme.”
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