Prostate Cancer Diagnosis
Several tests are used to diagnose prostate cancer.
Digital Rectal Examination (DRE)
In a DRE, the physician inserts a lubricated, gloved finger into the rectum to feel the surface of the prostate gland. Healthy prostate tissue is soft, like the fleshy tissue of the hand where the thumb joins the palm. Malignant tissue is firm, hard, and often asymmetrical or stony, like the bridge of the nose. However, as many as one-third of patients diagnosed with prostate cancer have a normal DRE.
Transrectal Ultrasound (TRUS)
TRUS is used to measure the size of the prostate and visually identify tumors. A probe inserted into the rectum emits ultrasonic impulses against the prostate. The images are projected on a monitor, so the physician can examine the gland and surrounding tissue for tumors.
TRUS and the digital rectal examination are effective prostate-cancer screening tools.
PSA and PAP Tests
Blood tests taken to check the levels of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) in a patient who may have benign prostatic hyperplasia help the physician eliminate or confirm a diagnosis of prostate cancer.
Prostate-specific antigen (PSA) is produced by the cells of the prostate capsule (membrane covering the prostate) and periurethral glands. Patients with benign prostatic hyperplasia (BPH) or prostatitis produce greater amounts of PSA. The PSA level also is determined in part by the size and weight of the prostate.
The test measures the amount of PSA in the blood in nanograms per milliliter (ng/mL). A PSA of 4 ng/mL or lower is considered normal; 410 ng/mL, slightly elevated; 1020, moderately elevated; and 2035, highly elevated. Most men with slightly elevated PSA levels do not have prostate cancer, and many men with prostate cancer have normal PSA levels. A highly elevated level may indicate the presence of cancer.
The PSA test can produce false results. A false positive result occurs when the PSA level is elevated and there is no cancer. A false negative result occurs when the PSA level is normal and there is cancer. Because of this, a biopsy is usually performed to confirm or rule out cancer when the PSA level is high.
Free and Total PSA (also known as PSA II)
PSA in the blood may be bound molecularly to one of several proteins or may exist in a free, or unbound, state. Total PSA is the sum of the levels of both forms; free PSA measures the level of unbound PSA only. Studies suggest that malignant prostate cells produce more bound PSA; therefore, a low level of free PSA in relation to total PSA might indicate a cancerous prostate, and a high level of free PSA compared to total PSA might indicate a normal prostate, BPH, or prostatitis.
Evidence suggests that the PSA level increases with age. A PSA of up to 2.5 ng/mL for men age 4049 is considered normal, as is 3.5 ng/mL for men age 5059, 4.5 ng/mL for men age 6069, and 6.5 ng/mL for men 70 and older. The use of age-specific PSA levels is not endorsed by all medical professionals.
Use the PSA Age/Race Quiz to determine your risk of prostate cancer.
Prostatic Acid Phosphatase (PAP) test
Prostatic acid phosphatase is an enzyme produced by prostate tissue. The level of PAP increases as prostate disease progresses.