PSA (prostate specific antigen) testing via a blood test in combination with a DRE (digital rectal examination), currently are the best screening tests available for the early detection of prostate cancer.
PSA (Prostate Specific Antigen)
PSA is a protein that is secreted by the prostate into the ejaculate fluid by a healthy prostate and one if its functions is to aid sperm movement. The PSA blood test measures the level of the PSA in the blood. Normally only very low levels of PSA are able to enter the bloodstream however in the case of prostate cancer and other prostate conditions, the normal barrier is disrupted resulting in increased levels of PSA being able to be detected in the blood stream. It is a useful tool for helping diagnose and monitor diseases of the prostate, but further tests are required to confirm whether prostate cancer is present.
PSA levels can rise due to prostate cancer or benign (non cancerous) conditions. Benign prostatic hypertrophy, urinary tract infections and prostatitis are all examples of non-cancerous conditions, which can cause PSA levels to rise. Recent ejaculation can also cause a temporary rise in the PSA readings. Only 1 in 3 men with an abnormal PSA result are found to have prostate cancer.
There are several aspects to the PSA result that are important indicators for the presence of prostate cancer. The absolute value of the PSA, the prior PSA history and rate of change of PSA (known as the PSA velocity) and the free to total PSA ratio are all taken into consideration prior to proceeding with further testing for prostate cancer. Very rarely prostate cancer can occur with very low PSA values and for this reason a PSA test should always be performed in conjunction with a DRE.
There is no PSA value where a man is guaranteed of not having prostate cancer. The higher the PSA, then the higher the risk of having prostate cancer. The absolute value of PSA where it is recommended that further testing should be undertaken varies however it is generally considered that a PSA of greater than 2.5 should be investigated further. The decision on whether further investigation is required should be a shared decision between the treating doctor and the patient, taking into consideration; the patient’s age, family history of prostate cancer, prior PSA history and DRE findings.
DRE (Digital Rectal Examination)
The Digital Rectal Examination is an examination of the back passage (rectum) to feel for any abnormal lumps or growths in the prostate which may indicate prostate cancer.
The bladder is the organ which stores urine and the urethra is the tube that drains urine out through the penis. The prostate lies immediately beneath the bladder and completely surrounds the urethra, lying immediately in front of the rectum.
During a Digital Rectal Examination, your doctor inserts a gloved finger into the rectum to feel the condition of the prostate that lies adjacent to the rectal wall. If the doctor feels any abnormality in size, shape or texture in the prostate, further tests may be carried out. Only part of the prostate can be examined and for this reason a DRE should not be performed in isolation and should always be done in conjunction with a PSA test.
An abnormal PSA or DRE do not definitely indicate the presence of prostate cancer. They indicate that an individual is at an increased risk of having prostate cancer and further testing is required to ascertain if prostate cancer is present.
The actual diagnosis of prostate cancer is made by way of biopsy, where tissue samples are taken during a procedure called a transrectal ultrasound guided prostate biopsy (TRUS). During the procedure a small ultrasound probe is inserted into the rectum and a series of pictures and measurements will be taken and the volume of your prostate will be calculated. A fine biopsy needle is then loaded through the ultrasound probe to take multiple specimens of prostate tissue. Normally 12 biopsies will be taken unless there are special circumstances in which case more biopsies will be taken, before being sent to a pathologist for assessment.