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Experts Urge Doctors to Use New PSA Values to Detect Prostate Cancer in African-Americans

Experts Urge Doctors to Use New PSA Values to Detect Prostate Cancer in African-Americans

Physicians screening African-American men for prostate cancer should use different cut-off points for a popular blood test because they will accurately detect 95% of cases in this high-risk group, according to a study published in the August 1 issue of The New England Journal of Medicine. The revised normal values for the prostate-specific antigen (PSA) test are based on a new diagnostic strategy and age-specific ranges for African-Americans, who have the world's highest prostate cancer rate.

"The new values will improve our ability to find prostate cancers without searching for disease that isn't there, a risk if the cut-off points are set too low," says Dr. Judd W. Moul, LTC, MC, USA. "This is especially important for a group with such a high risk." Dr. Moul headed the study group, which included doctors from Walter Reed Army Medical Center, Washington, DC; the Mayo Clinic, Rochester, Minnesota; and the Uniformed Services University of the Health Sciences, Bethesda, Maryland.

Previous studies had established that African-American prostate cancer patients have higher PSA values than Caucasians at all ages, and that they tend to be diagnosed with the disease at a later stage, when there is less chance for a cure. The situation has been difficult to remedy, however, because doctors have lacked a reliable set of normal PSA values for African-Americans.

To establish accurate normal PSA values, the researchers determined serum PSA levels for 3,475 men without clinical evidence of prostate cancer (1,802 Caucasians, 1,673 African-Americans) and 1,783 men with the disease (1,372 Caucasians, 411 African-Americans) and analyzed the results with respect to age and race. The analysis found that normal PSA values were significantly higher for African-Americans than for Caucasians. It also confirmed serum PSA as a valid screening tool for prostate cancer.

The doctors found that the traditional age-adjusted reference ranges continued to work well when applied to white men older than 40 years. But the first set of age-adjusted reference ranges they derived for African-Americans would miss 41% of prostate cancers in these men; this was clearly unacceptable.

Sensitivity-Based Test Developed for African-Americans

The problem was that the traditional strategy was designed to ensure that 95% of men who had normal PSA results did not have prostate cancer--that is, that the test was 95% specific. The higher the specificity of a screening test, the lower is its ability to detect all cases of a disease--its sensitivity. For African-Americans, a PSA test based on 95% specificity had a sensitivity that was too low. So, using their new PSA data, the researchers developed a sensitivity-based strategy for African-Americans that would catch 95% of prostate cancers without sending too many healthy men for biopsies.

According to this strategy, the normal PSA ranges for African-Americans are: 0 to 2.0 ng/mL for men in their 40s; 0 to 4.0 ng/mL for those in their 50s; 0 to 4.5 ng/mL for those in their 60s; and 0 to 5.5 ng/mL for those 70 years or older. The corresponding specificity rates for these age groups are 93%, 88%, 81%, and 78%. On a standard test measuring how well a screening tool balances specificity and sensitivity, the new ranges scored higher than both the widely accepted Pap smear for cervical cancer and mammography for breast cancer.

The clinicians caution, however, that the new reference ranges should be used only as a guide. They note that physicians should consider any other risk factors a patient may have for prostate cancer, as well as his age and life expectancy, any conditions that affect his general health, and, more importantly, his desire to undergo further evaluation to confirm the presence of prostate cancer. The decision to proceed with diagnostic testing should be made jointly by the patient and physician.

Prostate Cancer Survival

Prostate cancer is the most common cancer in men in this country and the second leading cause of cancer death, according to the American Cancer Society (ACS). Some 317,100 new cases will be diagnosed in 1996, and 41,400 men will die of the disease this year.

Among men treated for prostate cancer diagnosed at an early stage, ACS statistics show a 5-year survival rate of 98%. However, research has shown that this rate does not apply equally to African-Americans and Caucasians. Some men, for example, are thought highly likely to have curable cancers because presurgical examination indicates that their tumor is confined to the prostate. At surgery, however, more than 70% of African-Americans in this category, as compared with 30% to 40% of Caucasians, are found to have cancer cells escaping the margins of the gland, indicating that their disease is, in fact, more advanced.

"We hope our study will help raise doctors' awareness of the special need to diagnose prostate cancer as early as possible in African-Americans and will give them the tools to approach this goal," says Dr. Moul. He and his research team work as part of the Department of Defense Center for Prostate Disease Research, a congressionally mandated program to study prostate cancer in the tri-service military health-care system. The program is administered by the Henry M. Jackson Foundation for the Advancement of Military Medicine in Rockville, Maryland.

 
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