Screening and Diagnosis

The prostate specific antigen (PSA) blood test is widely available for screening men for prostate cancer. However, there is great uncertainty over whether regular screening has major benefits for most men. The most recent guidelines from the U.S. Preventive Services Task Force report that there is no conclusive evidence that routine prostate screening saves lives. Indeed, it may lead to invasive testing and treatments for many men who, considering the slow growth of the cancer, might derive no benefits from them. It is a difficult subject and men must discuss all aspects carefully with their doctor.

A 2006 study in the Archives of Internal Medicine also suggested that screening tests for prostate cancer may not reduce men’s risk of death. The small study of 1,000 men found no differences in survival between men who had prostate specific antigen tests or digital rectal exams, and men who were not screened. Doctors should inform men of the uncertainty of prostate cancer tests so that patients understand the relative risks and benefits of screening

Standard Screening Tests for Early Detection. Currently, two standard tests are used for early detection of prostate cancer:

• Digital rectal examination (DRE). With the DRE, a doctor palpates the prostate in order to feel lumps or masses.
• PSA test. The PSA blood test measures the level of a protein called prostate-specific antigen. It is able to detect early prostate cancer, although it has limitations.

If the digital rectal examination indicates the possible presence of cancer, regardless of the PSA results, a doctor may also obtain a visual image of the prostate through an ultrasound procedure called transrectal ultrasonography (TRUS). Only a biopsy, however, in which a tiny sample of prostate tissue is surgically removed, can actually confirm a diagnosis of prostate cancer.

Candidates for Annual Screening. Until major studies report on the survival benefits of prostate screening, expert groups recommend the following:

• Men ages 50 to 70 should be offered annual screening. (Some experts believe that men whose PSA levels are under 1.0 and possibly under 2.0 may safely be screened only every two years thereafter.)
• Men with a family history of prostate cancer and all African-American men should consider annual screening at about age 45.

The best age to start annual screening is under debate. Some experts advocate performing a first PSA test in all men aged 40 and then monitoring anyone whose PSA levels are over 0.60 ng/mL. They argue that such men are at high risk for developing prostate cancer within 25 years.

Digital Rectal Exam (DRE)

About 90% of all prostate cancers arise in the outer part of the prostate where they may be detected by a digital rectal exam (DRE), which is the simplest and most widely-performed screening procedure. The doctor inserts a gloved and lubricated finger into the patient's rectum and feels the prostate for bumps or other abnormalities. The exam is quick and painless but some men find it embarrassing. It is not very accurate in detecting early cancers, but studies indicate that regular DREs still save lives.

Prostate Cancer is the most common cancer in men in the United States. Prostate cancer forms in the prostate gland, and can sometimes be felt on digital rectal examination. This is one of the purposes of the digital rectal exam. The presence of cancer in

PSA Test

Prostate specific antigen (PSA) is a protein produced in the prostate gland that keeps semen in liquid form. Prostate cancer cells appear to produce this protein in elevated quantities. Measuring PSA levels increases the chance for detecting the presence of cancer when it is microscopic. There are many unresolved questions surrounding PSA testing. The test is not accurate enough to either completely rule out or confirm the presence of cancer. Relying too much on the test may lead to unnecessary biopsies. Not relying on it enough may miss cancers. It is still unclear if PSA testing is actually saving lives.

Click the icon to see an image of a PSA blood test.

Indications for Biopsy. A biopsy is usually performed to confirm or rule out cancer after screening tests that report the following:

• PSA level of 4.0 ng/mL or higher. Some evidence indicates that men with an initial test showing PSA levels above 4.0 should take a second PSA test several weeks afterward before having a biopsy, since many non-malignant factors can increase PSA levels. (Some experts urge biopsies even if PSA levels fall below 4.0 mg, particularly in men under 60, since lower levels do not necessarily rule out cancer.)
• Abnormal digital rectal examination (DRE).

Men with abnormal results from both tests have a 60% chance of prostate cancer. The chances for cancer if only one test is abnormal are considerably lower. To further complicate matters, biopsies themselves may miss very small cancers detected by PSA levels alone.

Factors Affecting PSA Levels. A number of factors and noncancerous conditions can influence PSA levels:

• Ethnicity. Normal levels in Caucasian males may be different from those for African-American or Asian men. For example, using PSA screening, one study suggested that 15% of Caucasians and 37% of African-Americans are overdiagnosed with prostate cancer based upon PSA results. Some experts believe that there should be different scales for determining risk among these groups, but there is still not enough information to determine a specific range for various ethnic groups.
• Age. PSA levels tend to rise naturally with age, so an elevated level in a man who is 70 may be less serious than the same level in a younger man. Some experts believe that men older than 65 who have low PSA levels are at such low risk for prostate cancer that they may be able to forgo further testing.
• Benign Prostatic Hyperplasia (BPH) and Its Treatments. Between 25 - 56% of patients with BPH have elevated PSA levels. Certain treatments for this condition can also elevate PSA.
• Prostatitis. About half of men with elevated PSA levels but no signs of cancer on biopsy have signs of prostatitis as indicated by urine and prostate secretion tests. (Prostatitis simply means inflammation in the prostate. Inflammation is usually due to bacterial infection but it can also be caused by nonbacterial factors.) In one study, screening for prostatitis increased the accuracy of the PSA test significantly and reduced the number of unnecessary biopsies.
• Other Noncancerous Conditions. Other noncancerous conditions that can increase PSA levels include surgical procedures or drug treatments for BPH, acute urinary retention, digital rectal examinations, and prostate biopsies themselves.
• Ejaculation. Ejaculation within 48 hours before testing can raise PSA levels, although one study suggested that this occurs only when PSA levels were already elevated.

Even with its limitation, the PSA test has increased the number of detectable early-stage and therefore treatable cancers. Because of the slow-growing nature of prostate cancer, however, it is not known whether all of these very early cancers will result in significant or life-threatening disease. It is possible that PSA screening could result in the detection of some possible cancers that would never have bothered the patient and would never have posed a threat to his life.

PSA Test Variations

To improve the accuracy of the PSA tests, particularly when PSA levels have risen to an intermediate range of between 4 and 10 ng/mL, researchers are developing methods for measuring other factors. To date, no test has emerged as clearly superior to the PSA test.

Free PSA Test. A small amount of prostate specific antigen leaks out of the prostate into the bloodstream. There, PSA can circulate without binding to other proteins and is referred to as free PSA. It can also form chemical combinations with other proteins. If cancer is present, PSA is more likely to be bound, and so there is less free PSA in circulation. The free PSA blood test, then, is a ratio of free PSA to the total PSA (free PSA plus chemically bound PSA).

The following results are used to determine if an elevated PSA level could mean cancer:

• A free-to-total PSA ratio of 20% or lower, plus total PSA levels of 4 to 10 ng/mL, are suggestive of prostate cancer. (Some experts use 25% as a cut-off, but studies suggest that using this cut-off would miss cancers in many African American and older men.)
• A free-to-total PSA level of more than 20% plus normal or even moderately elevated total PSA tend to indicate the presence of other, benign conditions, such as benign prostatic hyperplasia (but it still does not rule out cancer).

Some studies have reported that adding a test for free PSA may improve prostate cancer detection by roughly 40% and may also reduce the need for unnecessary biopsies. In addition, any cancers that the test misses would not develop into significant disease for many years, providing ample opportunity to identify them before they became serious. Not all studies support its advantages, however, compared to measuring total PSA alone, and to date there is no consensus among doctors for how it can be used.

Complexed PSA Test. Complexed PSA (cPSA) is a form of circulating PSA that is bound to a molecule called alpha1-antichymotrypsin. It represents about 90% of the total PSA in men and is significantly higher in men with prostate cancer than in those with BPH. To date, studies have reported conflicting results on its benefits for diagnosing prostate cancer, although a major 2002 European study was very favorable.

Transition Zone PSA Test.Some tests have been developed to measure the density of the PSA in the transition zone of the prostate gland. (The transition zone is the central area of the prostate that wraps around the urethra.) A major comparison study in 2002 reported more accurate results than with complexed PSA.

Ultrasound (Transrectal Ultrasonography)

An ultrasound procedure called transrectal ultrasonography (TRUS) provides a visual image of the prostate and is used if the DRE indicates the presence of cancer. Ultrasound is not effective as a diagnostic tool by itself because it cannot differentiate very well between benign inflammations and cancer, but the procedure may help to confirm an uncertain preliminary diagnosis and is useful as a guide for needle biopsies. Ultrasound enhancements, such as Doppler imaging or computer modeling techniques called artificial neural networks (ANN), may increase the accuracy of TRUS.

Biopsy

Initial Biopsies. If preliminary tests raise the suspicion of cancer, doctors will perform a biopsy. Biopsy is used to diagnose prostate cancer, and is a very accurate method for predicting the severity of an existing cancer. However, biopsies can still miss cancers if they are very small.

• Core Biopsy. The standard method is called a core biopsy, which uses a spring-loaded biopsy device inserted into the rectum. The device propels a needle into the prostate, obtaining a core of tissue, which is examined by pathologists.
• Fine Needle Aspiration. A more recent procedure called fine needle aspiration is less painful and may be as accurate as a core biopsy if the sample obtained is sufficient for analysis and if it is analyzed by a skilled pathologist.

More than half of the men who have a biopsy experience discomfort and anxiety, with men under 60 reporting higher levels of discomfort than older men. Taking a sedative 1 - 2 hours before the procedure can help reduce distress. Complications of biopsy are low, but urinary tract infection, fever, or bleeding occurs in 0.1 - 4% of men.

Repeat Biopsies. Because a biopsy can miss very small cancer cells, sometimes three or even more biopsies are recommended if cancer is still suspected after negative results, such as in the following circumstances:

• PSA levels are high. Two or more biopsies may be taken if a man has very high PSA levels and still has normal results on a biopsy. Even men with mildly elevated PSA (between 4 and 10 ng/mL) who test negative may be given a repeat biopsy. Cancer will be detected in about 10% of this group. Whether a third biopsy is useful in these men if they still test negative after a second biopsy is uncertain.
• DRE results are abnormal.
• Ultrasound results are abnormal.
• The initial biopsy yields microscopic findings that are suspicious.
• The initial biopsy detects precancerous cells known as high-grade prostatic intraepithelial neoplasia (PIN). No treatment is necessary with this finding, but these patients should be rechecked every 3 to 6 months for the next 2 years, and then annually.

Doctors may also perform a lymph node biopsy to see if the cancer has spread.