CARPINTERIA, Calif—A newly available fluorescent-based immunocytologic test to detect superficial bladder cancer, ImmunoCyt, used in conjunction with urinary cytology, will likely reduce the need for periodic cystoscopies in patients with transitional cell bladder cancer and enhance the early detection of recurrent disease.
"Examination of the urine under the microscope has been found to be an inadequate way to detect recurrent bladder cancer. It requires patients diagnosed with bladder cancer to undergo frequent cystoscopic monitoring once surgical removal of any cancer has taken place," said Edward Messing, MD, chairman, Department of Urology, University of Rochester School of Medicine, Rochester, NY.
Because of this ongoing need to monitor for recurrences, "tests that may lessen the need for such invasive procedures as cystoscopy would be welcomed," Dr. Messing said during a telephone press conference. He emphasized the importance of detecting low-grade tumors as soon as possible.
"ImmunoCyt utilizes three monoclonal antibodies specific for two antigens expressed on the tumor cell surface," said Edward Barker, MD, PhD, who moderated the conference. Dr. Barker is a pathologist and president of Molecular Oncology International, Seattle, an independent laboratory involved in evaluating the immunologic test.
With ImmunoCyt, Dr. Barker said, bladder cancer cells are collected from a urine sample, filtered, spread on a slide, stained with the fluorescently labeled antibody mixture, and scanned under darkfield microscopy for the presence of red and/or green fluorescence on transitional cells. The cost of the test is about $250.
ImmunoCyt is licensed by DAKO Corporation of Carpinteria, California, from DiagnoCure, Inc. of Quebec City, Canada. The US Food and Drug Administration granted commercial clearance for the ImmunoCyt test in March 2000.
Antibody Detects Mucin, CEA
The antibodies used in the ImmunoCyt kit are designed to detect a mucin glycoprotein and a modified form of the carcinoembryonic antigen (CEA). Importantly, the CEA antigen scored for by this test is separate and distinct from the CEA antigen associated with colon cancer, diminishing the possibility for cross-reactivity that could yield inaccurate results.
Dr. Barker pointed out that conventional cytology detects low-grade tumors only about 40% of the time. When ImmunoCyt is used in conjunction with cytology, this sensitivity rate increases to roughly 95%. Moreover, the specificity of these combined tests ranges from 50% to 75%.
Michael Carter, MD, a urologist from Kelowna General Hospital, British Columbia, Canada, reported similar sensitivity rates. "We performed ImmunoCyt tests on urine samples obtained from 34 patients previously diagnosed with abnormalities on cystoscopy and detected 32 transitional cell cancers," Dr. Carter said. "In our laboratory, the overall sensitivity of ImmunoCyt plus cytology was 90.6%," he said, adding that at this level of accuracy, the likelihood of a false-negative result is very low.
Dr. Messing said that "the single most immediate advantage of this immunocytology test is its potential to reduce cystoscopies required of patients with a more indolent form of bladder cancer," which should also increase patient compliance with the necessary continual monitoring for recurrence. For example, the manufacturer’s suggested monitoring schedule for a low-risk patient (single tumor with negative cystoscopy exam at 3 months) is Immunocyt plus cytology every 6 months and cystoscopy every 12 months.
Dr. Messing also said that while future large-scale prospective studies are needed to fully evaluate the utility of such immunology-based cytology tests, the current data are a good first step toward increasing the detection rates of bladder cancer.
Notably, additional data in close to 60 patients from Dr. Carter’s studies are pending and should bolster these initial results.
