Prostate Cancer Screening

About

The prostate is a gland that helps make semen (the fluid that contains sperm) in men. It is about the size of a walnut and surrounds the tube that carries urine away from the bladder. It grows larger with age. Three most common problems that rise are infection (prostatitis), abnormal enlargement (Benign Prostatic Hyperplasia or BPH), and cancer. Prostate cancer is a leading malignancy in men over the age of 50. Early detection of prostate cancer is important.

PSA (Prostate Specific Antigen) test and Digital Rectal Examination are two tests that allow detection of prostate cancer at early stages.

More about PSA

PSA is prostate specific and not cancer specific marker as it maybe elevated in conditions other than prostate cancer like benign conditions such as prostatitis and prostate gland hypertrophy.

PSA function is to liquefy semen and keep it watery. Most of this protein is eliminated from the body through the semen; however, small measures of this antigen enter the blood stream and can be found in the blood serum.

PSA can either be attached to another compound or may exist by itself:

Attached PSA- This is a type of PSA which is complexed or attached to the protease inhibitor, alpha -1 antichymotrypsin.

Free PSA - This PSA is free and is not complexed to any molecule.

Total PSA -This is the sum of both the attached and the free form of the PSA

In a standard PSA test, total PSA is usually measured. This is done by taking a blood sample and analyzing the amount of PSA. The amount of PSA in the blood is very low, therefore specific tests, such as the monoclonal antibodies, are employed to carry out the test.

Individuals with prostate cancer tend to have low percent of free PSA compared to those with the benign disease.

Normal concentration of PSA is 0-4 nanogram/ml. This concentration can vary with age. Normally, the prostate gland enlarges in older men and this leads to the increased production of PSA.

Age-specific normal PSA levels are given below:

• 40 - 49 yrs - 2.5ngms/ml
• 50 - 59 yrs - 3.5 ngms /ml
• 60 - 69 yrs - 4.5ngms /ml
• 70 - 79 yrs - 6.5 ngms /ml

PSA levels not only rise in the case of prostate cancers but also in the case of many conditions of the prostate such as:

• Benign prostatic hypertrophy (BPH)
• Prostate bladder or kidney infections
• Poor blood supply to the prostate
• Urinary retention

PSA also increases after a prostate surgery or after exams or procedures such as biopsies, catheterization or digital rectal exam.

In many cases, PSA is also carried out to check recurrence in a person with prostate cancer. Increased levels of PSA are definitely indicative of recurrence although a single PSA test may not be sufficient to confirm it.

It may be interesting to note that the PSA levels increases much before the clinical symptoms of prostate cancer manifest themselves and hence they provide a window of opportunity to cure the cancer before it spreads to other parts of the body. They are also useful in the follow up of the patients who has been treated. Any persistent elevation is considered as recurrence of the cancer.

Sometimes PSA tests reveal small tumors that are not life-threatening. However this will prompt unnecessary treatment initiation. There are also several cases of false positives reported.

Digital Rectal Examination

Is a clinical examination to look for enlargement of the gland and to know if it is benign or malignant? It is done in the clinic on the doctor's couch with the person lying on the back or the side and the knees drawn up.