In the US alone annually there are about 1,000,000 prostate cancer biopsy procedures carried out of which around 25 percent show the presence of cancer. Of the remaining 75 percent of biopsies however approximately one-third also produce false negative results. This means that about a quarter of all men having prostate biopsies are being cleared by this test, in spite of the fact that they actually have prostate cancer.

On the surface therefore it might appear that the cancer biopsy is not a very efficient test but these results do not in fact show that there is anything wrong with the biopsy as a tool for diagnosing the presence of cancer. What it does show however is the need to detect those patients who, despite they have returned a negative result, are nonetheless at considerable risk from cancer and ought therefore to have a second follow-up biopsy.

The problem is that until now there has not been a simple method of identifying patients who are at risk. However, a recent study of more than 500 men being investigated for the presence of prostate cancer could now provide an answer.

All of the patients who took part in the study had already had a negative biopsy result but the researchers discovered that when they studied the patient's prostate specific antigen test results and these were adjusted for the size of the prostate gland they were able to identify those patients who were more likely to return a positive result on a follow-up biopsy.

The researchers also found that men who had a Gleeson score of 7 or higher were at greater risk from life-threatening cancer and were again more likely to produce a positive result on a second biopsy. The Gleeson score is measured on a scale between 2 and 10 and a patient's score is calculated from a laboratory investigation of the biopsy tissue. A low score points to a cancer with a relatively small risk of spread and a high score points to a cancer which is much more likely to spread.

There are a variety of different biopsy procedures in use nowadays although perhaps the most frequently performed procedure is the core needle biopsy. In this case several very small tissue samples are removed from different parts of the prostrate gland using a biopsy gun which fires a needle into the chosen area and removes the sample in just a fraction of a second. These samples are then sent off for laboratory examination to determine whether or not cancer is present and, if it is, to estimate precisely how much of the prostate gland is affected.

A prostate cancer biopsy is an expensive procedure and is one which can also be quite distressing for the patient. It can also be a quite painful test which may involve bleeding and the risk of infection. As a result it is in everyone's interest to detect those men for whom a follow-up biopsy would be sensible and to reduce as far as we can the number of unnecessary follow-up biopsies being performed each year.