A biopsy is removal of pieces of tissue so it can be examined under the microscope to evaluate the cell structure. These can be performed a number of way, it can be a surgical, where the surgeon cuts you open and literally cuts out a piece of tissue. Normally for a prostate we use a trans-rectal method. An ultrasound probe is inserted into the rectum with a needle placed on it. The prostate is visualized using ultrasound then the needle is inserted into the gland and sections of tissue pulled out. This is normally repeated 6-12 times depending on the facility. Obviously the more samples taken, the better the chances of getting cancerous cells, it they’re there.
Now the issues. As you can see from the diagram above, there is a lot of variation in the position of the probe since it is controlled by a human. Ideally, as in the diagram you would position the probe such that the needle takes a sample through the middle of the tumor.
But nothing in life is that easy. You can’t see the tumors under ultrasound guidance your are shooting blind so this is more likely what will happen:
So the earlier the stage of the cancer, the smaller it probably is, and the greater chance the biopsy will miss it, as in the diagram above.
The next issue which is a whole new subject is the pathologist now has to pick the right bit of tissue to look at. You might assume they look at all of it, but they don’t. If in the following diagram the red represents the prostate gland and the gray the tumor. The pathologist cannot necessarily see the tumor until he/she gets it under a microscope. If there are 24 cores I can assure you they will not look at every cell, it would just be impossible.
There are also complications as a result of putting a needle through the rectal wall into the prostate. It can cause infections, and in extreme cases rectal fistula’s (a hole in the rectal wall). Usually the patient is given antibiotics as part of the biopsy to reduce complications, but they still occur.
So what is the solution. There are new tests coming that will give better information regarding tumors in the prostate such as the MRI with the endorectal coil.
This begs the question, given the complications of the biopsy, the inaccuracies, what do we recommend. I would still get a biopsy. If I have a high PSA and get a negative biopsy I would watch the PSA closely (every 3 months), if it continues to climb, get another one. I can’t tell you the number of patients I have seen that have been through this 5 or more times and finally they get a positive biopsy. It is my personal belief that if you have a high PSA and you have ruled out BPH and prostatic infection then you have prostate cancer……