Enzyme Test for Bladder Cancer May Promote Early Diagnosis
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Measuring levels of the enzyme telomerase in urine may be a simple, inexpensive, and accurate way to detect bladder cancer early, according to investigators here.
About 20% of bladder cancer patients die each year, but chances of survival are good when the disease is diagnosed and treated in the early stage, the investigators said.
However diagnosis of bladder cancer is often delayed because symptoms such as hematuria are intermittent and can be attributed to common, benign disorders such as urinary tract infections, prostatitis, and renal stones. As a result patients with such symptoms often are not screened for cancer with cystoscopy, the current gold standard for diagnosing bladder cancer—but invasive and expensive.
For these reasons, and because urine cytology lacks sensitivity, especially for low-grade tumors, a better alternative is needed, the Italian research team said in the Oct. 26 issue of the Journal of the American Medical Association. Telomerase was chosen as a possible marker because elevated levels have been found in nearly all human tumor histotypes.
In a study of more than 200 men, the telomeric repeat amplification protocol (TRAP) achieved a sensitivity of 90%, which is equal to that of cytoscopy, reported Daniele Calistri, Ph.D., of the Morgagni-Pierantoni Hospital here and colleagues.
The TRAP test requires a small amount of urine and is noninvasive, inexpensive, and easy to perform, the researchers said. Furthermore, it is objective, reproducible, and not reliant on the expertise of a cytopathologist, they added.
The study included 218 men-84 healthy individuals and 134 patients with a first diagnosis of histologically confirmed bladder cancer. Urine samples from all patients were processed for cytological diagnosis and TRAP assay. The TRAP assay, which was performed in a blinded fashion, was compared to urine cytology for ability to detect bladder cancer.
Using a cutoff value of 50 arbitrary enzyme units, the sensitivity of the TRAP test was 90% (95% confidence interval=83%-94%) and its specificity was 88% (95% CI=79%-93%).
In a subgroup of patients 75 or younger, the sensitivity increased to 94% (95% CI=85%-98%).
The sensitivity of the TRAP test was similar for low-grade and high-grade tumors. For grade 1 tumors, the sensitivity was 93% (95% CI=70%-99%). For grade 2 tumors, the sensitivity was 87% (95% CI=76%-94%). And for grade 3 tumors, the sensitivity was 89% (95% CI=79%-85%).
“Indeed, one important advantage of this test is its proven ability to also identify low grade tumors, which often escape detection, thus largely contributing to false-negatives in cytologic examination,” the study authors wrote.
“However, notwithstanding the validated optimal diagnostic accuracy of the test, it is not recommended for use in routine screening programs because of the low incidence of bladder cancer, and should be aimed at high-risk subgroups. Specifically, smokers have about a 3-fold increased risk of developing bladder cancer compared with nonsmokers,” the authors concluded.
The current study was not designed to demonstrate that screening with the TRAP test improved survival or quality of life, two key criteria for accepting a new screening method, noted Herman Kattlove, M.D., M.P.H., speaking for the American Cancer Society.
Source: Journal of the American Medical Association
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