The prostate gland produces higher levels of a protein called PSA in response to the presence of cancer. "Normal" PSA levels, however, can vary from person to person, while cancer patients may not show elevated PSA at all.
PSA stands for prostate-specific antigen, a protein produced by the prostate gland.
Doctors recommend PSA testing for men once they reach the age of 50. The test measures PSA levels in the bloodstream. PSA levels under 4 nanograms per millileter generally indicate the absence of cancer.
No single PSA level seems to fit all patients. The National Cancer Institute mentions one study in which 65 to 75 per cent of patients with high PSA levels did not have prostate cancer. If "normal" PSA varies from case to case, then doctors must watch for sudden changes in an individual's PSA level.
In addition to prostate cancer, natural ageing or certain non-cancerous conditions can also raise PSA, according to the American Cancer Society.
The Mayo Clinic warns that prostate cancer may exist even without an abnormal change in PSA levels. This type of cancer may in fact prove more aggressive and spread faster than other varieties.
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