Many patients ask if we’re going to do another prostate biopsy after the radiation therapy is finished, to prove that the prostate cancer is gone. Unfortunately, if we biopsy the prostate gland after radiation is completed, two problems may occur.
#1 If the biopsy shows cancer cells, these cells may actually be “fatally wounded” cancer cells that haven’t completely died off yet. They are destined to die like a 103 year old in a nursing home, they cannot divide and produce any new cancer cells, but they still show up on the biopsy. You need to wait up to 3 years after radiation for all of these “fatally wounded” cancer cells to vanish! This is also called a “false positive” result. The test may be positive, but it is not true.
#2 If the biopsy does not show any cancer, this is good news, but it does not prove there is no cancer. There still could be cancer “hiding” in other areas of the prostate gland. When the urologist does a biopsy he sticks a needle into the prostate gland in about 12 areas, but there is also tissue between those 12 samples! This is also known as a “false negative” result.
Doing a biopsy after radiation is not accurate because of all the false positives and false negatives. So should a biopsy ever be done after radiation treatment? Occasionally. Basically when all of the following four conditions are met:
- Two or three years or more have passed since radiation.
- The PSA is above 1 – 2 and is climbing. Preferably it is at least 2 points above the lowest PSA measurement that was obtained since radiation.
- There is no cancer in the rest of the body — CT and bone scans are clear.
- Your doctor believes that the cancer has recurred in the prostate and is suggesting retreatment with another aggressive prostate therapy like surgery or cryotherapy.
In the case where all 4 conditions are met, yes, another biopsy should be done. Doing a re-treatment of a prostate gland can cause a lot of symptoms and it is better to have some proof that there is still cancer there before going down that road.
Q) Should a biopsy be done after prostate radiation to prove the cancer is cured?
A) Hardly ever. It usually won’t prove anything due to the number of false positive and false negative results.