DIAGNOSING PROSTATE PROBLEMS: PSA TESTS: AN OVERVIEW
An article in Cancer Journal provides an overview of this clinical dilemma in screening for prostate cancer. It states that any current diagnostic test can decrease mortality, but new information about optimal combinations of DRE, transrectal ultrasound, and the PSA test suggest that their combined predictive values can identify not only men at high risk but also those for whom continued frequent screening may not be cost-effective.
According to Dr. Ralph W. deVere White and associates from the University of California at Davis, PSA levels obtained from urine can be as accurate as those from blood. The team evaluated forty-three patients following radical prostatectomies and found that 77 percent of the patients had elevated urinary PSA, while only 33 percent had elevated serum (blood) PSA levels. They concluded that following surgery, close to 80 percent of the patients had tumor-bearing prostate tissues remaining locally, which the standard PSA blood tests did not recognize.
Overall, the study revealed that most men's urinary PSA level matched the blood serum PSA level, except following surgery. The investigators noted that after radical prostatectomies, urine PSA elevations were twice as common as elevated blood serum PSA levels. This suggested to the team that more patients have residual cancer than has previously been suspected.
The investigators will have to do more research before they are ready to claim that postoperative clinical treatment will be required for men whose urine PSA level is elevated while their blood serum PSA level is not.
Despite the shortcomings of the PSA test, the American Cancer Society and the American Urological Association recommend annual PSA testing for men beginning at age fifty, or at age forty if their family history puts them at a high risk for cancer. "Better to overdiagnose than underdiagnose," says cancer researcher Curtis Mertlin, "because by the time we find 40 percent of these cancers, it's too late to cure them."
Bob Dole, whose cancer was detected with the PSA test, encourages others to be tested. "I'm one of the many men who consider themselves living proof that early detection can mean a healthy future. Please have routine checkups, and don't neglect to have your doctor check for prostate disease. It could save your life."
It is interesting to note the attitudes of Europeans regarding diagnostic tests for prostate cancer. In northern Europe, PSA and DRE tests are not routinely used. Doctors there are concerned that indiscriminate use of these tests will lead to overdiagnosis and overtreatment. Information on the effectiveness of treatment from randomized trials is unavailable, and no evidence exists that early diagnosis and treatment will lead to an improvement of disease-related and overall mortality.
PSA vs. Quality of Life A new study adds more fuel to the debate. A JAMA report concluded that screening all men for prostate cancer is not cost-effective and doesn't significantly extend life. Based on the analysis, screening all men once, using the PSA test and a DRE, would add only six days to the life expectancies of fifty-year-old men and 1.7 days for seventy-year-old men. However, critics say that the report was based on statistics and assumptions and not clinical data.
Dr. Gerald Chodak, Professor of Surgery at the University of Chicago, is a vocal critic of the American Cancer Society's recommendations regarding PSA testing. "What I am for is providing better information to patients," he told Modem Medicine. "We don't know that screening will lower mortality from prostate cancer.
Until we do, the ACS shouldn't be making recommendations, and we should not be telling patients that screening will save their lives."
This argument doesn't make sense to Dr. Gerald P. Murphy, former Chief Medical Officer at die American Cancer Society. "We're not finding cancers that don't need treatment," he says. In one study of men who were diagnosed with prostate cancer by PSA and DRE, 85 percent of the cancers found were clinically significant.
PSAs, DREs, and Early Screenings A study that speaks highly of the PSA when performed in conjunction with a DRE was cited by Dr. E. David Crawford at die University of Colorado Health Sciences Center in Denver. He presented results obtained from 25,954 men who had prostate exams. Among a subgroup of 4,035 patients who had follow-up biopsies, 41.6 percent of those with elevated levels of PSA were found to have prostate cancer. Of the patients who had abnormal DREs, only 20 percent had prostate cancer. A positive predictive value of 44 percent was found when both tests were used.
"If you believe that screening is a worthwhile endeavor, then the combination of the two tests is better than either one alone," he told Modern Medicine. These data confirm the results of a 1991 study conducted by researchers at Washington University School of Medicine in St. Louis, Missouri, which concluded that the PSA test appears to be reliable. The researchers also determined that the combination of PSA testing and rectal examination with ultrasonography performed in patients with abnormal findings provides a better method of detecting prostate cancer than rectal examinations alone.
The PSA test is beneficial for early screening of cancer, according to a more recent study conducted by Dr. Charles Hennekens of Harvard Medical School and Brigham and Women's Hospital in Boston. It involved data from a continuing research project that included 22,071 doctors who were forty-two to eighty-four years old in 1982.
A survey to estimate the incidence of prostate cancer in Olmsted County, Minnesota, from 1983 through 1992 concluded that the increase is due in part to the expanded utilization of PSA testing; the more testing that is done, the more cancer will be found. The study also suggested that in terms of making a diagnosis, early detection efforts may be effective in identifying more early-stage, smaller cancers.
The PSA test can be valuable for patients who have prostate cancer and want to adopt a wait-and-see approach rather than go right into surgery. "A doctor who discovers a patient has prostate cancer must always ask the question, 'How big is the cancer?' As long as it's less than a milliliter in volumeabout the size of a sugar cubethe patient doesn't need any therapy. He is far more likely to die of something else long before the prostate, cancer spreads enough to bother him," said Dr. Thomas Stamey. To keep tabs on a tumor, doctors should monitor the patient with an annual PSA blood test, Stamey said. If the tumor grows larger, the patient may be a candidate for surgery.
The PSA test is also a good way to monitor the progress of prostate cancers after surgery or radiation treatment. Dr. Anthony Zietman, a radiation oncologist at Massachusetts general hospital (MGH), recently completed a study that affirmed die value of PSA tests in determining the most appropriate course of treatment and in predicting the likelihood of patients remaining cancer-free. Study results indicate that understanding the significance of specific PSA levels prior to treatment can help determine which patients will do well with radiation therapy alone and which patients will benefit from more aggressive treatment combining radiation therapy, surgery, and endocrine therapy. Establishing a baseline PSA level is important so it can be monitored to see how it is affected by a form of treatment.
Though PSA testing has been used routinely as a follow-up tool after prostate cancer treatment, the results of the MGH study indicate that by lowering what is considered an acceptable level of PSA, a recurrence of cancer can be detected earlier, allowing further treatment to begin at a more beneficial stage.
It is still undetermined whether the PSA test given yearly will reduce the death rate. The National Cancer Institute recently began a trial of 37,000 men, which v/ill help to answer that question in ten years.
During the tracking stage, it is important to remember that there are actually two types of PSA: complexed and free. Since different tests will weigh the two types in a dissimilar manner, the results reported by different labs can be confusing to a patient. Fortunately, this is about to change. An international group of researchers, clinicians, and pharmaceutical executives from around the world met recently and agreed to use a common standard for reporting PSA test results.
*25\284\2*
Men's Health Erectile Dysfunction