Clinical Features : Prostate cancer
By prostate Doc at 8 September, 2008, 4:28 pm
At presentation, 60% of patients have localized disease and only 15% have dis- tant metastases at presentation since the PSA era. The majority of patients are either asymptomatic or have bladder outlet symptoms, such as urgency and frequency. Patients with metastatic disease most often complain of bone pain which can be in the low back, secondary to the distribution of veins into the lumbar area and a path for metastatic spread.
Renal failure from ureter obstruction or anemia and low back pain may be initial signs of metastatic disease. Detection of prostate cancer is usually by digital rectal examination (DRE) and prostate specific antigen (PSA) testing. Transrectal ultrasound is insensitive and is rarely used for screening. Recommenda- tions for PSA testing are somewhat controversial, but recommended by most uro- logical organizations and should start at age 50 for an annual PSA examination and age 40 for those with a positive family history. PSA was identified in 1979 and came into usage in the mid-1980s. PSA is an antigen expressed exclusively in the prostatic epithelium and is a serine protease with a half-life of 2.2 days. PSA is expressed in normal prostate epithelium and is increased 10-fold per gram in prostate cancer cells. Despite being nonspecific it remains a valuable screening tool for the detection of prostate cancer. Other causes of PSA elevation include prostate infections, benign prostatic hyperplasia (BPH) and after vigorous digital rectal examination or imme- diately following ejaculation. PSA is elevated in 80-90% of men with prostate can- cer. However, cancer can occur 10-20% of the time with normal levels of PSA. Recently, the fractionated PSA and bound PSA tests have been used to differentiate elevations of PSA from malignant versus benign processes. The percentage of PSA unbound to protein is measured and levels beyond 25% free PSA are associated with a low incidence of prostate cancer approaching the normal population. Medications can suppress PSA levels resulting in false-negative tests. Finasteride, an 5-alpha-reductase inhibitor used for treatment of BPH and baldness, will lower PSA by an average of 50% in a benign prostate and a lower percentage in prostate cancer. Also, patients who have had surgical or medical castration will have dramatically lower PSA values, and herbal medications frequently taken in the population may also lower PSA slightly. Herbal compounds containing phytoestrogens such as PC Spes have been found to lower PSA also.
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