How is Prostate Cancer Diagnosed?

Introduction

Prostate cancer causes no symptoms in the early, curable stages and men will not know that they have prostate cancer unless they see a doctor and are checked for prostate cancer. By the time prostate cancer causes urinary symptoms, pain or weight loss it is usually too late to cure prostate cancer. In the past prostate cancer was called the "silent killer" because so many men were unaware that they had prostate cancer until it was too late. Before the modern era of PSA testing for prostate cancer 60% of men had advanced, incurable prostate cancer by the time it was diagnosed. With modern PSA testing 90% of prostate cancers are detected while they are still curable. Since the introduction of PSA there has been a 25% decrease in the number of men dying of prostate cancer in the U.S. Several recent studies indicate that prostate cancer screening can lower the chance of dying of prostate cancer. If initial screening tests suggest the possibility of prostate cancer men are referred to a urologist for evaluation, and a prostate biopsy may be recommended to determine if prostate cancer is present. In rare cases prostate cancer is diagnosed after a transurethral resection of the prostate (TURP) for benign prostate enlargement.

Prostate Cancer Screening

There are two parts to the prostate cancer screening exam, a blood test called PSA and a digital rectal examination, or DRE. The DRE is performed by the doctor, who will place a finger into the rectum and feel the prostate to determine its size, shape, and consistency. The normal prostate is symmetric with a uniform, rubbery texture. Any lumps, firm areas, or asymmetry can be signs of prostate cancer and may need further investigation. Roughly 10-20% of prostate cancers are detected by the DRE.

The most common way that prostate cancer is suspected is by an elevated PSA blood test. PSA stands for prostate-specific antigen, and PSA is a protein which is made only by the prostate and works to help liquify the semen after ejaculation. A very small amount of the PSA made by the prostate "leaks" into the blood where it can be measured by a simple blood test. If the PSA is elevated there is a 30% or higher chance of prostate cancer and further investigation may be necessary.

Normal total PSA by age
40-50 yrs	0-2.5
50-60 yrs	0-3.5
60-70 yrs	0-4.5
> 70 yrs	0-6.5

When the PSA test was first developed a normal value of 4.0 was set for all men. We now know that the average PSA rises as men age, and most urologists use age-specific PSA ranges to determine who is at risk for cancer (shown at right). Within the past few years a new type of PSA test called free PSA has been developed to try to better determine which men with elevated PSA tests need to undergo prostate biopsy. Most of the PSA in the blood is "stuck" to other proteins, but some is floating "free" in the blood. The percentage of "free PSA" can give some information about a man's risk for prostate cancer. If the free PSA is very low (less than 10%) there is a high risk of prostate cancer, and if the free PSA is high (over 35%) the risk of prostate cancer is low. At MBUA we usually go by the total PSA to determine who needs a prostate biopsy because the free PSA test has not been proven to be more accurate than the total PSA, but we consider the results of the free PSA test in certain patients.

What happens if the PSA or DRE are abnormal?

If the PSA or DRE are abnormal there is the possibility that a man has prostate cancer. If the PSA is between the normal value and 10 there is a 30% risk of prostate cancer, and if the PSA is greater than 10 there is at least a 50% risk of prostate cancer. If the PSA is normal but the DRE is abnormal the risk of cancer varies depending on how abnormal the exam is, but approximately 10-20% of men with prostate cancer have a normal PSA. In order to determine if a man has prostate cancer a prostate ultrasound and prostate biopsy must be performed (click here to learn more about the biopsy procedure).

If the prostate biopsy is positive for cancer the urologist will analyze a number of factors which can help to predict how serious a cancer the patient has. You can learn more about these factors at the page entitled "How do patients choose the right treatment." If the biopsy is negative for cancer then the urologist and the patient will discuss a schedule for future checkups.