Prostate cancer has no symptoms in the early stages, but it can be detected with a simple blood test. Elevated levels of a protein called prostate specific antigen (PSA) signal the presence of prostate cancer. Because PSA levels rise due to other prostate conditions, such as an inflamed or enlarged prostate, further tests must be done to confirm the diagnosis.
Prostate Cancer
Cancer of the prostate, a small gland at the base of the scrotum, is associated with high survival rates, primarily because it is usually detected in the early stages. Prostate cancer often grows slowly and may not be immediately life-threatening when it is first detected.
What is PSA
In addition to male hormones, the prostate gland produces a protein called prostate specific antigen (PSA). Low levels of PSA normally circulate in the blood of healthy men (NCI). Elevated PSA levels, however, may indicate prostate cancer. Prostatitis (inflammation of the prostate) or benign prostatic hyperplasia (prostate enlargement usually related to aging) may also cause a rise in PSA levels but does not lead to cancer.
PSA Test
Elevated PSA levels are a biological marker for cancer. The PSA blood test is often combined with a digital rectal exam, in which the physician feels the size and shape of the prostate gland through the rectal wall. If the PSA test or rectal exam reveal abnormal findings, additional tests, such as a prostate biopsy, may be performed. Although higher PSA levels suggests a stronger likelihood of cancer, no cutoff has been established indicating normal and abnormal levels. PSA levels naturally fluctuate; therefore, a single elevated PSA level may not necessarily indicate the need for further testing. A trend of rising PSA levels over time better predicts the presence of cancer. PSA tests are also used to monitor progress after completion of prostate cancer treatment. Increasing PSA levels usually signal the recurrence of cancer, and levels begin rising months or even years before other symptoms begin.
Screening Recommendations
No clear-cut guidelines exist for using the PSA test to screen for prostate cancer. Some guidelines call for annual PSA tests for all men older than 50 years whereas others recommend screening to begin between the ages of 40 to 45 years only for men at higher risk for prostate cancer. Risks for prostate cancer increase with age (older than 65 years); a family history of prostate cancer, particularly in a father or brother; and race. African-American men are more likely to develop prostate cancer compared with men of other races. Men who consume a diet high in animal fats are also at increased risk.
PSA Test Limitations
Despite its usefulness as an early indicator of cancer, the PSA test has limitations. An elevated PSA level may result from conditions other than cancer, or a single elevated level may be a normal fluctuation. Up to 35 percent of men who have a prostate biopsy because of elevated PSA levels are found not to have cancer. Conversely, cancer may be present even though PSA levels are low.
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