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Prostate cancer
Description
An in-depth report on the causes, diagnosis, treatment, and prevention of prostate cancer.
Tests to Determine Severity of Cancer
PSA Levels and Velocity
Once cancer is diagnosed, PSA levels may help to determine its extent. If PSA levels are less than 20 ng/mL, it is possible that the cancer has not spread to distant sites. PSA levels over 40 ng/mL are a strong indicator that cancer has metastasized (spread throughout the body). PSA levels are also monitored after treatments begin. Changes in the level can show if a treatment is working or if the cancer has come back.
Doctors also monitor how quickly PSA levels rise over time. This rate is called PSA velocity (PSAV). The PSAV is very helpful in determining when treatment should begin and which treatment should be used. A high rate of PSAV is considered to be 2 ng/mL a year. Recent research suggests that men with early-stage prostate cancer who have a slow PSAV are more likely to live longer than men with rapidly rising PSA levels.
Biological Markers
A number of biological factors are being used or investigated as markers for cancer or its severity:
Chromosomal Sets. The number of chromosomal sets in the nucleus of the tumor's DNA, known as its ploidy, is an important marker for patients in late stages of prostate cancer. Tumors with the normal two sets of chromosomes, called diploid tumors, usually have a more favorable outcome than tumors that have four sets of chromosomes (tetraploid tumors) or have an abnormal number of individual chromosomes (aneuploid tumors).
Blood Vessel Density. The density of blood vessels in the tumor is an important indicator of outcome. The greater the density, the more likely the tumor is to be aggressive.
Serum Acid Phosphatase. High levels of this enzyme indicate a more aggressive disease and the need for intensive treatments.
Testosterone Levels. Higher total testosterone levels may increase the risk for metastasis. A 2000 study found an association with low free testosterone and more extensive prostate cancer, suggesting free testosterone could be a marker for aggressive disease. (Free testosterone, as with free PSA, is not chemically bound.)
Genetic Markers. Researchers have identified a genetic marker (EZH2), which may prove to be an important marker for aggressive prostate cancer. It may, in fact, prove to be a better predictor of outcome than the tumor grade, stage, or surgical margins. Other genes beings studied are those that regulate tumor growth (p53, p27, bcl-2).
Other Markers. Other markers being investigated for predicting cancer progression include prostate-specific membrane antigen, prostatic acid phosphatase, and growth factors.
Nuclear Imaging Tests
The ProstaScint is a scanning technique that uses tiny amounts of radioactive material with a monoclonal antibody that can attach specifically to prostate cancer cells. A special camera then can detect tumor cells that cannot be detected with other diagnostic tools. It may be effective in helping doctors make better treatment decisions. The role of this test in the routine management of prostate cancer is still being defined.
Tests for Metastasis
If the biopsy indicates cancer, the doctor will order other tests to determine whether or how far the cancer has spread.
Bone Scans and X-Rays. Bone scans and X-rays may reveal whether the cancer has invaded the bones. To perform a bone scan, doctors inject low doses of a radioactive substance into the patient's vein, which accumulates in bones that have been damaged by cancer. A scanner then reveals how much of the radioactive material has accumulated. Arthritis and infections may also produce positive scans. Patients with PSA levels below 20 ng/mL are unlikely to have scans that show cancer in the bone.
A radiotracer is injected into a peripheral vein. As the radiotracer decays, gamma radiation is emitted and is detected by a Gamma camera. When the tracer has collected in the target organ the area is scanned. Radionuclide scans can detect abnormalities such as fractures, bone infections, arthritis, rickets, and tumors that have spread, among other diseases.
Computed Tomography and Magnetic Resonance Imaging. Computed tomography (CT) or magnetic resonance imaging (MRI) scans can further pinpoint the location of cancer that has spread beyond the prostate. Advanced MRI techniques are showing promise for staging and planning treatments.
Bone Metastasis Markers. Researchers are investigating chemical markers, such as a amino-terminal propeptide of type I procollagen (PINP), as early indicators of bone metastasis.
- Review Date: 7/9/2006
- Reviewed By: Harvey Simon, M.D., Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital.
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