Screening

DRE

A digital rectal examination (DRE) is a quick and safe screening technique in which a doctor inserts a gloved, lubricated finger into the rectum to feel the size and shape of the prostate (See picture below). The prostate should feel soft, smooth, and even. The doctor examines for lumps or hard, irregular areas of the prostate that may indicate the presence of prostate cancer. The entire prostate cannot be felt during a DRE, but most of it can be examined, including the area where most prostate cancers are found.

When a tumor is small and located only within the prostate, it is often not detected during a DRE. However, if an abnormality is found during the DRE, the new ACS guidelines suggest a prostate biopsy, even if the PSA is normal.

Prostate-specific Antigen (PSA)

Prostate-specific antigen (PSA) is a substance produced by both normal and cancerous prostate cells. When prostate cancer grows or when other prostate diseases are present, the amount of PSA in the blood often increases.

A PSA test is generally said to be in the normal range when it is reported to be between 0 and 4 nanograms per milliliter, sometimes abbreviated as ng/mL on the lab report.

If the results are greater than 4 ng/mL, your physician may suggest a biopsy, which is the only test available to diagnose prostate cancer.

Guidelines published in 2005 by the National Comprehensive Cancer Network (NCCN) suggest that the threshold for consideration of a biopsy should be lower. The NCCN guidelines now recommend consideration of biopsies for men with PSA levels in the range of 2.5 to 4.0 ng/mL.¹

It may also be useful to keep track of how your PSA level changes over a period of time. If your PSA level is rising your physician may suggest a biopsy.

PSA test results can be confusing and do not mean that cancer is present. Certain other conditions, such as benign prostatic hypertrophy (also called BPH - a type of noncancerous prostate enlargement) and prostatitis (inflammation of the prostate), may cause an abnormal PSA result.

Additional PSA Tests

Because borderline PSA tests can be confusing, your physician may advise you to consider having one or more of the newer PSA tests. These are described below:

Percent Free-PSA Ratio

Percent free-PSA ratio is a blood test that measures how much PSA circulates by itself (unbound) in the blood and how much is bound together with other blood proteins. If PSA results are borderline and percent free-PSA ratio is low (25% or less), then prostate cancer is more likely to be present. If this is the case, a biopsy may be needed.

If the results of the percent free-PSA ratio are greater than 25%, even with a borderline PSA, you may be able to avoid a biopsy.

Complexed PSA (cPSA) is another test that measures PSA bound to a substance called alpha-1-antichymotrypsin.

The Age Factor

Another way of looking at PSA involves age-specific PSA reference ranges. PSA levels increase with age; therefore, higher PSA levels are normally seen in older men more often than in younger men, even without cancer. An age-specific PSA reference range compares the results of men in the same age group. If a man’s PSA levels are high compared to his own age group, then there is a greater chance that prostate cancer could be present. In older men with borderline PSA results, this comparison can be more confusing than useful. As a result, age-specific PSA reference ranges are not routinely done.

PSA Density

If you have had your PSA measured and also have had a transrectal ultrasound (TRUS), then PSA density (PSAD) can be determined. To calculate your PSAD, your physician will divide the PSA by the size, or volume, of the prostate (determined from the TRUS). There is a greater chance that prostate cancer is present with a high PSAD.

PSA Velocity

Finally, PSA velocity shows how quickly the PSA level rises over a period of time. Two or more PSA tests are required, often over several months of time. Although PSA velocity may be useful in helping your doctor better interpret borderline PSA results, it is not really used to diagnose prostate cancer. Instead, it is used more as a tool to keep track of how your PSA levels compare over a period of time.

PSA often rises as part of the natural aging process; an increase in the PSA from time to time does not necessarily indicate that prostate cancer is present. On the other hand, if PSA increases too quickly (as determined by your physician), prostate cancer is a possibility.

PSA-DT

If you have been diagnosed with prostate cancer, another factor your doctor may consider is PSA doubling time (PSA-DT), which is the time it takes your measured blood PSA levels to double. Generally, a shorter PSA-DT indicates that the prognosis of your prostate cancer may be worsening.

Newer PSA tests can be useful, but they are still too new for physicians to agree on when and how they should be used. If your PSA is borderline or abnormal, your doctor can help you determine which tests, if any, are right for you. A high PSA doesn’t necessarily mean that prostate cancer is present, and a low or normal PSA doesn’t always mean that prostate cancer isn’t present. In other words, the PSA test may provide false results. Therefore, it is used along with the results of the DRE to provide more accurate screening.

TRUS

If your PSA test results are borderline high, but your DRE results are normal, then your doctor may recommend a transrectal ultrasound (TRUS). During TRUS, a small probe is placed in recturn. This procedure causes little discomfort.

As illustrated below, this is a procedure that uses sound waves to create a picture of the prostate, which can be used to help identify abnormal areas requiring a biopsy. If the results of the TRUS are normal, you may be able to wait and repeat the PSA test a few months later and have a biopsy then if needed.

A transrectal ultrasound of the prostate.

How Is Prostate Cancer Detected?

The American Cancer Society (ACS) has developed guidelines to help doctors detect prostate cancer during its early stages. The ACS has recently revised these guidelines to reflect new scientific literature. The guidelines recognize that prostate cancer screening, including a digital rectal examination (DRE) and a test to measure prostate-specific antigen (PSA) in the blood, should be offered yearly to the general male population 50 years of age and older.²

In addition, males at increased risk for developing prostate cancer, such as men with a first-degree relative (father, brother, or son) affected by the disease or those of African-American descent, should consider annual screenings beginning at age 45. Men at even higher risk because they have several first-degree relatives who had prostate cancer at an early age should begin annual screenings at age 40.²

There are some instances in which prostate cancer screening may not be recommended. Because prostate cancer can be a slow-growing cancer, a man with a less than 10-year life expectancy would most likely die of some other illness, and, therefore, is not very likely to benefit from prostate cancer screening and treatment. For this reason, the new ACS guidelines include a statement for patients explaining the risks and benefits of prostate cancer screening. These guidelines can be found on the Internet at: www.cancer.org or by calling the American Cancer Society at 1-800-ACS-2345.

You and your physician can discuss the ACS guidelines together and determine if screening is right for you, and, if so, when you should begin.

References

1. Prostate Cancer Early Detection Clinical Practice Guidelines in Oncology. JNCCN, 2005. Available at: www.nccn.org. Accessed July 11, 2005.
   
   
2. American Cancer Society. Detailed Guide: Prostate Cancer. 2005. Available at: http://www.cancer.org/docroot/CRI/CRI_2_3x.asp. Accessed July 11, 2005.
   
   

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