Prostate Cancer Screening and Detection
There are several ways to screen for prostate cancer and the recommendations for when these screenings should begin vary, depending on a number of factors.The American Cancer Society recommends that men with no symptoms of prostate cancer who are in relatively good health and can expect to live at least 10 more years have the opportunity to make an informed decision with their doctor about screening after learning about the uncertainties, risks, and potential benefits associated with prostate cancer screening. These talks should start at age 50. Men with no symptoms who are not expected to live more than 10 years (because of age or poor health) should not be offered prostate cancer screening.
Men at high risk: African-American men and men who have a father, brother, or son diagnosed with prostate cancer before age 65 -- begin those conversations earlier, at age 45. Men at higher risk-those with multiple family members affected by the disease before age 65 -- should start even earlier, at age 40.
Digital Rectal Examination and PSAProstate biopsy prompted by abnormal findings on digital rectal exam (DRE), such as nodularity or induration of the prostate leads to a diagnosis of prostate cancer in only 15%-25% of cases. This compares with prostate cancer prevalence of less than 5% among men of similar age without abnormal DRE. Although neither accurate nor sensitive for prostate cancer detection, abnormal DRE is associated with a 5-fold increased risk of cancer present at time of screening.
PSA Screening has revolutionized prostate cancer screening. PSA is a serine protease produced by the prostatic epithelium and secreted in the seminal fluid in large quantities. Prostatic disease changes the cellular barriers that normally keep PSA within the ductal system of the prostate and thereby alters serum levels. The level of PSA in serum is increased by inflammation of the prostate, urinary retention, prostatic infection, benign prostatic hyperplasia, prostate cancer, and prostatic manipulation.
Like DRE, PSA is, therefore, neither accurate nor optimally sensitive for prostate cancer screening; only 15%-25% of cases with PSA greater than 4.0 ng/dL are found to have prostate cancer on biopsy.
Mi-Prostate ScoreFor men with an elevated PSA, the University of Michigan Health System has begun offering a new urine test called Mi-Prostate Score to better assess the risk of cancer being present. The test developed from a discovery by U-M researchers of a genetic anomaly that occurs in about half of all prostate cancers, an instance of two genes changing places and fusing together.
This gene fusion, T2:ERG, is believed to cause prostate cancer. Studies in prostate tissues show that the gene fusion almost always indicates cancer.
The new urine test looks for the T2:ERG fusion as well as another marker, PCA3. This is combined with the PSA measure to produce a risk assessment for prostate cancer. The test also predicts risk for having an aggressive tumor, helping doctors and patients make decisions about whether to wait and monitor test levels or pursue immediate biopsy.
The test is available to anyone but requires a request from a doctor. For further information, have your doctor's office can call the University of Michigan's MLabs at 800-862-7284.
BiopsyWhen indicated, prostate biopsy usually is performed as an office procedure by transrectal ultrasound guidance using an automated 18-gauge biopsy gun. The procedure is done without the need for anesthesia and carries a risk of significant infection of only 1 in 200. Some blood in the urine or in bowel movements can be common for 2-3 days following the biopsy. Blood in the semen may last for up to 2-3 weeks.
If the biopsy is negative, these men are typically followed by checking PSA and rectal exam annually. Repeat biopsy may be needed if PSA levels rise at abnormal rates (less than 0.8 ng/dL/year) or if rectal exam shows new nodularity or induration. Men in whom high-grade prostatic intraepithelial neoplasia is found on biopsy may undergo repeat biopsy, since about one-third will be found to have prostate cancer.
One caveat to PSA screening is its lack of specificity when the value lies between 4 and 10ng/cc, since many men with benign prostatic hyperplasia have PSA levels in this range. There have been several attempts to increase testing specificity, including the development of age-specific ranges, trends in PSA increase over time (PSA velocity), and calculations of the PSA density based on the volume of the prostate gland. A commonly employed test to increase testing specificity in this 'indeterminate zone' is the percent-free PSA. Currently, biopsy is recommended in men whose percent-free PSA is less than 10%, while biopsy is not necessary when percent-free PSA is less than 25%.
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