The prostate is a gland the size of a walnut which lies in the male pelvis in front of the rectum and around the outlet of the bladder.

To examine the prostate, the doctor inserts a finger into the patient’s rectum and can then feel the back surface of the prostate through the wall of the rectum. This exam is used to help detect any abnormality.

If serious suspicion of abnormality exists, biopsy of the prostate is the next step. This is the process of placing a needle into the prostate to obtain tissue for microscopic examination. The microscopic exam will tell if there is any cancer in the sample.

Nowadays the most usual method of biopsying the prostate uses a slim ultrasound probe passed into the rectum. The ultrasound produces an image of the gland which helps guide the doctor to the areas to biopsy. A special needle is then used to remove a tiny piece of the prostate for examination for cancer.  Presently, this is the standard method and should be the main approach when the decision to biopsy the prostate is made.  However, we are learning that there are more limitations to the standard approach than previously thought. This methods of biopsying the prostate, although very useful, can miss some cancers. A new generation of the prostate biopsy technology is now available and has the promise of missing fewer cancers.

The standard approach to prostate biopsy was improved in the 1990’s when studies showed that using an ultrasound to target certain areas of the prostate was better than relying on finger-guided biopsies alone.  Since that time most urologists use a grid system with 12 to 13 zones to target. They use the ultrasound to facilitate taking a biopsy sample from each of those areas from the rectal side of the prostate. However some cancers still cannot be seen or are difficult to recognize under ultrasound. Therefore, the goal of the standard approach is to SAMPLE every zone of the prostate, rather than to directly TARGET lesions that might be cancers. This can result in missing some cancers. See Figure 1.

Figure 1: Multiple prostate biopsies can miss a cancer.     X = Biopsy         = cancer

The prostate is a 3–dimensional object, which causes the standard approach to have another limitation.  Because the trans-rectal ultrasound probe is at the rectal/posterior surface of the prostate, the other (anterior) side tends not to be biopsied unless the whole needle is pushed into the prostate before taking a tissue sample. See Figure 2.  In addition, as men age the prostate will often enlarge which increases the distance from the rectal side to the anterior side.  Luckily, most prostate cancers do not develop on the deeper/anterior side.  But when they do, the standard method can miss them.

Figure 2: Limitation to Biopsy Anterior Prostate