Study questions benefits of screening for prostate cancer

SCREENING FOR prostate cancer does not significantly reduce deaths from the tumour and may cause both over-detection and over-treatment, a long-term study published this morning has found.

In a trial involving more than 9,000 Swedish men who were followed up for 20 years, researchers from the Karolinska Institute and the University of Linkoping found that screening for prostate cancer using a combination of a rectal examination and a blood test did not prolong the survival of those men who developed the disease.

Prof Gabriel Sandholm and his colleagues randomly selected some 1,500 men for prostate cancer screening every three years, starting in 1987, with the 7,500 others acting as controls. All men with cancer diagnosed up to the end of 1999 were included in the analysis, with survival figures followed until 2008.

There were 85 cases (5.7 per cent) of prostate cancer diagnosed in the screened group and 292 (3.9 per cent) in the control group.

This difference was not statistically significant. However, the tumours found in the men who were screened were smaller and more localised within the gland than those diagnosed opportunistically, suggesting that screening is detecting cancers that are low-risk because of their slow rate of growth.

Among the strengths of the study, which is published online by the British Medical Journal, is the fact that all of the men diagnosed with prostate cancer were treated in a single urology centre using the same treatment decision protocols.

Also, Swedish disease and death registry records are extremely accurate because every citizen has a unique patient identifier.

The main risk factor for prostate cancer is advanced age, with 80 per cent of cases occurring in men over the age of 65. In many instances, the cancer is non-aggressive, so that the lifetime risk of dying from prostate cancer is 3 per cent. The prostate gland lies just under the bladder and surrounds the urethra; it secretes fluid that nourishes sperm and provides most of the volume of semen.

Approximately 2,400 men develop prostate cancer in Ireland annually. About 550 men here die each year from the disease, with men in the west experiencing the highest death rates.

A diagnosis of prostate cancer is usually made by a combination of a rectal examination and the finding of an elevated prostate specific antigen (PSA) in the blood.

The most recent all-Ireland 10-year cancer report found a significant difference in the apparent incidence of prostate cancer in Northern Ireland compared with the Republic, which it said was probably due to over-testing for PSA by doctors here.

The authors of the Swedish study conclude: “Before undergoing prostate-specific antigen testing, asymptomatic men should be informed about the potential hazards of treatment.”