Prostate cancer is most often diagnosed by an asymptommatic elevation of one's PSA value as found on a blood test during a routine physical examination. Prostate cancer rarely causes symptoms at its early stages. The majority of prostate cancers arise in the peripheral (outer) portion of the gland. As a result, a nodule that is palpated on rectal examination should warrant further evaluation with a biopsy to rule out cancer. A decrease in urinary stream, hesitancy and frequent urination are all symptoms that most often correspond to an enlarged prostate that occurs with aging. In its advanced stages, prostate cancer can also be responsible for these symptoms. The digital rectal examination (DRE) along with the blood test for PSA are the main modalities utilized to detect prostate cancer. If either the PSA value is elevated or a prostate nodule is noted on DRE, then a trans-rectal ultrasound guided (TRUS) biopsy of the prostate is performed.
Digital Rectal Examination (DRE)
A rectal examination is an integral part of any complete physical examination. Duriing the rectal examination the prostate can be examined and palpated for any nodularity. The physician is actually feeling the peripheral portion of the prostate where most cancers arise. A palpable nodule, regardless of one's PSA value, should warrant a biopsy. Although only 20-50% of these nodules will reveal cancer, a biopsy should still be undertaken. In addition, approximately 25% of men with prostate cancer will actually have a normal PSA value, lending more importance to the digital rectal examination.
Prostate-Specific Antigen (PSA)
PSA is a protein produced by the prostate and periurethral glands in the male. It is involved physiologically in helping liquefy the semen prior to ejaculation. PSA circulates in the blood in both the bound and unbound forms. In the bound form, the PSA molecule is bound to protein called alpha-1-antichymotrypsin (ACT) to form a PSA-ACT complex which is detectable on blood immunoassays. The "free" or unbound form of PSA is the "inactive" form of PSA and is also detectable on blood tests. The free plus the bound form are equal to the total PSA value. Most blood tests report on the bound form of PSA. The unbound or "free" PSA has more recently been used to increase the specificity of the PSA test in detecting prostate cancer. The half life of the PSA molecule is 2-3 days and thus after ones of 0-4 is considered "normal." This, however, has changed over the last few years. The concept of age-specific PSA has been introduced. Age specific normal are listed below.
- Age 40-50: 0-2.5ng/ml
- Age 50-60: 0-3.5ng/ml
- Age 60-70: 0-4.5ng/ml
- Age 70-80: 0-5.5ng/ml
The PSA value increases with age mostly as a result of the growth in size of the prostate with age. Although somewhat controversial, the concept of the age-specific PSA evolved as an attempt to increase earlier detection in young men who will benefit from the treatment while at the same time decrease unnecessary biopsies in older men. Other concepts that have emerged in an attempt to improve the PSA test are listed below:
- PSA velocity - the rate of change of PSA over time. An increase in PSA of 0.75ng/ml or above over a year should initiate a prostate biopsy.
- PSA density(PSAD) - PSA value divided by the size of the prostate. A PSAD of 0.15 or above should initiate a biopsy.
Trans-Rectal Ultrasound Guided Biopsy (TRUS)
TRUS biopsy of the prostate utilizes an ultrasound probe that is passed into the rectum that uses sound waves to visualize the prostate on a monitor. Through direct visualization of the prostate, a special biopsy needle can be safely and accurately introduced into the prostate to perform both random biopsies and directed biopsies of nodules. Usually, sextant biopsies are taken of the prostate and a total of six cores are obtained for pathological examination. Oral antibiotics are administered before and after the procedure and patients are sent home the same day. The entire biopsy lasts approximately 15 minutes. Patients may notice some blood in their urine after the biopsy which should resolve within a few days.