US multicenter study led by Dr. William J. Ellis of the University of Washington has found that the new, quantitative BTA TRAK Assay improves the detection of recurrent bladder cancer over cytology, the standard microscopic method. These results were reported in the December 1997 issue of Urology.
In the double-blind study, 144 patient samples with histologically confirmed bladder cancer were compared using the assay and urine cytology. Overall, the sensitivity of the BTA TRAK assay (68%) was significantly better than that of urine cytology (25%). The combination of both methods yielded only a small increase in sensitivity, which was not significantly different than that of the assay alone.
The BTA TRAK Assay is a new tool for monitoring bladder cancer that potentially could be used in the same way as PSA [prostate-specific antigen] for prostate cancer, said Dr. Ellis, associate professor in the Department of Urology and the studys lead author. Because it provides quantitative levels that physicians can follow over time, we are hoping that it allows us to perform cystoscopy less often.
The BTA TRAK test is an enzyme immunoassay that uses two monoclonal antibodies to measure a newly identified bladder tumor-associated antigen in human urine. This antigen has been characterized as a human complement factor H-related protein (hCFHrp), which is related, but not identical to, human complement factor H (hCFH). Like hCFH, hCFHrp may confer a selective growth advantage to cancer cells by protecting them from the patients own immune system.
Sensitivity Increases With Increasing Stage and Grade
The study showed that mean assay values increased with progressing stage and grade of disease, with the greatest sensitivity in high-grade disease. However, even in low-grade bladder cancer, the assays sensitivity was 54%, in contrast to only 7% for cytology.
The study also noted that the assay is significantly more sensitive than the original BTA Test, which measures a complex of molecules shed from the bladder wall. The original BTA Test was approved by the FDA in 1995. The BTA TRAK assay is awaiting FDA clearance but is currently available in Europe and other countries outside the United States.
Some 53,000 Americans are diagnosed with bladder cancer each year and approximately 500,000 people are routinely monitored for it in the United States. The cancer is most common among people over the age of 50, smokers, and workers exposed to chemicals in the rubber, leather tanning, metal, and dye industries. Bladder cancer is one of the most highly curable types of cancer, if detected early. Its recurrence rate, however, is between 50% and 80%, making life-long monitoring an essential health maintenance component.