No evidence for benefits of prostate cancer screening

By Lilian Anekwe

BMJ Group News

What do we know already?

Prostate cancer occurs when some of the cells in a man’s prostate gland begin to grow out of control, invading and destroying healthy cells. As men get older their chances of getting cancer of the prostate rise.

To detect prostate cancer, doctors often use a test called a digital rectal exam (DRE) to see if a tumour can be felt through the wall of the rectum. Another method is the prostate-specific antigen (PSA) blood test. PSA is made in the prostate but can leak into the blood for a number of reasons, including if there is a cancer in the prostate.

A PSA test can suggest a cancer may be present, but cannot tell for certain whether you have prostate cancer.

In recent years, experts have been looking closely at the PSA test to see if it can be used to screen for prostate cancer, in the same way as the NHS uses mammograms to screen for breast cancer in women.

But there is no definite evidence that detecting and treating prostate cancer early improves your chances of surviving the disease. We are still unsure if regular PSA testing will cause more unnecessary worry and harm than good.

In one large cancer screening trial nearly 77,000 men aged 55 to 72 were divided randomly into two groups. One group of men were given annual PSA tests for six years and then an annual DRE for four years. A second group of men had usual care, with some having tests for prostate cancer during routine appointments if they asked for one, or if their doctor suggested it.

After seven years, the researchers found no difference in the number of men who survived prostate cancer, or how long they lived. Now, the researchers have followed up with the men 13 years after the study began, to see whether there were any positive benefits of prostate cancer screening over a longer period.

What does the new study say?

After 13 years, 4,250 men in the screening group and 3,815 men in the usual care group were diagnosed with prostate cancer.

Combining all the years that the men had been followed since the study’s start, the researchers calculated that there were 108 men diagnosed with prostate cancer for every 10,000 years of follow-up in the screening group, compared with 97 men in the usual care group. This worked out as a 12 percent increase in the number of prostate cancers diagnosed in the screening group.

Of the people diagnosed with prostate cancer in the two groups, 158 men in the screening group and 145 in the usual care group died as a result of their cancer. This worked out as around four deaths for every 10,000 years of follow-up for the screening group and three deaths for the usual care group, but this difference was not more than would be expected purely by chance.