Prostate Cancer and PSA

With more than 217,730 men estimated to be diagnosed with Prostate Cancer in 2010 and almost 32,050 deaths from the disease, this disease warrants attention.

So I decided to share with you certain facts related to Prostate cancer so as to try to dispel myths that are propagated in magazines, books and online media.

Lets look at the Prostate gland itself first.

Prostate gland resides at the base of the penile shaft. It surrounds the urethra and has a size of a plum. The cells in the gland secrete PSA an enzyme used to de-clot the semen to allow the sperms that are produced in the testicles, to flow. The prostatic fluid is rich in citrate and zinc has an alkaline pH to counter the germ-protective acidity in the female vaginal fluid. Simple enough, right?

Let us discuss PSA, which has notoriously been the subject of derision and confusion. As mentioned PSA is an enzyme it is maximally present in the ejaculated seminal fluid. Some, very little, of it gets into the blood stream even in people with healthy normal prostate glands and that is registered in the laboratory tests.

As the prostate gland enlarges, as happens in benign prostatic hypertrophy or (BPH), the value of PSA rises many-fold. So that brings up the issue of its (PPV) positive predictive value of this test in prostate cancer.

The PPV, not to get too technical is the ability of a test to predict the presence of disease, in this case prostate cancer.

The lab test value considered as the cut-off for such prediction is placed at 4 ng/ml. The PPV of just PSA alone is 23%. This means that 4 out of 5 people with this lab test will NOT have prostate cancer.

Based on some other studies, if the PSA is then complemented with a digital rectal examination (DRE) by a urologist (physician) the value of the combined DRE and PSA rises to 36-47% or 2 of the 3 people with the combined test will NOT have prostate cancer.

Now if we are to add a Transurethral Ultrasound or (TRUS) the PPV becomes 53% or 1 of 2 people with all these tests indicating suspicion will yield a diagnosis of prostate cancer.

Individuals at risk for Prostate Cancer:

1. African-American men, who, are also likely to develop cancer at every age.

2. Men who are older than 60

3. Men who have a father or brother with prostate cancer

4. Other people at risk include:

5. Men exposed to agent-orange exposure

6. Men who abuse alcohol

7. Farmers

8. Men who eat a diet high in fact, especially animal fat

9. Tire plant workers

10. Painters

11. Men who have been exposed to cadmium

So do all individuals need all three? The answer is not so, unless you are at a high risk to begin with that include African American heritage, a strong family history or have a known specific mutation of the BRCA1 or 2 tumor suppressor gene in addition to those features mentioned above.  Also if PSA screening test has revealed a value higher then 4 ng/ml then these additional tests may be needed prior to an interventional prostate biopsy.

Also of note and of equal importance is that PPV is lower in the 5^th decade as compared to the 6^th and the 7^th decades. In other words the older the person, the presence of an abnormal PSA level leads to a higher probability of prostate cancer.

Another beneficial test for further defining the value of an abnormal PSA is the Free-PSA. This test is used in individuals with PSA value between 4-10 ng/ml. If the result shows higher level of free PSA in percentage of total the better the chance that the PSA value is NOT indicative of cancer.

One last note on PSA is some belief that PSA itself may have some anticancer properties by inducing apoptosis of the pre-malignant cells. This data has not been verified.

Again as always it is important for all individuals to confer and seek answers from their treating physician to remain fully informed and objective in the decision making process.

References:

1. American Cancer Society. Cancer Facts & Figures 2010. Atlanta, Ga: American Cancer Society; 2010

2. Use of prostate specific antigen (PSA) and transrectal ultrasound (TRUS) in the diagnosis of prostate cancer--a local experience.Tan HH, Gan E, Rekhraj I, Cheng C, Li MK, Thng P, Tan IK, Yo SL, Poh WT, Foo KT.Department of Urology, Singapore General Hospital, Singapore Ann Acad Med Singapore. 1995 Jul;24(4):550-6.

3. http://www.medscape.com/viewarticle/525087_3