Value of prostate tests dubious

Jan 10 2006

According to new research, men screened for prostate cancer using blood tests or digital examinations die of the disease at much the same rate as those who were not checked.

Prostate cancer is the most common cancer among men, with more than 27,000 new cases and about 10,000 deaths every year in the UK alone, and it is the second leading cause of cancer deaths in American men after lung cancer.

John Concato, a doctor at the Yale School of Medicine who led the study, says this suggests that for the tens of thousands of men being screened for prostate cancer with the prostate specific antigen (PSA) test, the screening is not effective.

The PSA test detects the disease by measuring the amount of a protein produced by the cancer.

PSA, produced in the prostate, is in the blood of healthy men, and cancer in the gland can increase its levels, but a similar increase can be caused by benign enlargement of the gland or by prostate infections.

Blood samples are tested for PSA levels, with higher levels indicating a greater risk of the disease.

But the test is highly controversial as it does not pick up some early cancers, and about two thirds of men with a positive PSA test do not have prostate cancer at all.

Nor can the test tell if the cancer is life-treating or merely a harmless “passenger” that will never spread or be a serious problem.

Doctors currently check for it with a digital exam of the small gland and by measuring the level of PSA in the blood.

A positive result often causes anxiety and entails a painful biopsy; a positive result may mean a prostate operation that can leave men impotent and incontinent, without ever being sure that they needed it.

However the study has been criticized by the Washington-based National Prostate Cancer Coalition who say the researchers should have taken other factors into consideration but concede a better biomarker for prostate cancer is needed.

Concato's team concludes that routine tests of healthy men should not be endorsed as a way of reducing deaths, but it should be recognized that substantial uncertainty exists regarding the usefulness of PSA screening among healthy men and the limitations of the test should be discussed with a doctor.

Concato's study was based on a review of the medical records of 1,000 men age 50 or older who had received care at veterans hospitals in New England, half of whom had died of prostate cancer.

It concluded that if PSA testing is effective in preventing death, it would be expected that more men who were still alive had been screened than those who had died.

But in fact, the opposite was found, as 14 per cent of the men who died had been screened, compared with 13 per cent of those who survived.

It found the rate of PSA tests among the deceased was about the same as for the rest of the men who were still alive.

The study is published in the Archives of Internal Medicine.