More dependable, less expensive tool to detect bladder cancer earlier
Feb 16, 2005 - 7:41:38 PM
Physicians now have a more dependable, less expensive tool to help detect bladder cancer earlier.
Researchers at The University of Texas M. D. Anderson Cancer Center found that a simple test that can be administered and read in the doctor's office was three times more effective than a conventional laboratory test for detecting bladder cancer.
In a study published in the February 16 issue of the Journal of the American Medical Association, researchers tested the NMP22 tumor marker assay in 1,331 patients at high risk for bladder cancer. Researchers determined through cystoscopy that 79 of the 1,331 patients examined had bladder cancer. The NMP22 assay was positive in 55 percent of the cases (44 out of 79 cases) while the conventional cytology test detected about 16 percent of malignancies (12 out of 76 cases).
This demonstrated that the NMP22 test was significantly more sensitive than cytology, or the conventional laboratory test, says H. Barton Grossman, M.D., professor in M. D. Anderson's Department of Urology and the study's lead author.
"Our challenge is to improve the detection of bladder cancer," says Grossman. "This test is easy and may save lives."
He cautions, however, that NMP22 should not be used alone to detect bladder cancer, but should be combined with bladder examination (cystoscopy) to provide an accurate diagnosis.
"No single procedure is 100 percent sensitive, so a combination of procedures is recommended," Grossman says.
The findings are seen as an advance in screening for bladder cancer, Grossman says, which is the fifth most common cancer in the United States. Five-year survival is 95 percent for cancer caught early, but it is much lower for the 25 percent of bladder tumors that are advanced when first diagnosed. It is estimated that more than 60,000 people living in the U.S. will be diagnosed with bladder cancer this year; 13,000 are predicted to die of the disease.
Grossman led a team of researchers at M. D. Anderson and 23 academic, private practice, and veterans' facilities in 10 states who enrolled patients into the clinical trial that examined the effectiveness of these different diagnostic tests.
Patients enrolled in the trial were suspected of having bladder cancer because they had evidence of blood in their urine and met some of the risk factors associated with the disease, which include a history of smoking, exposure to certain chemicals, being over age 40 and painful and frequent urination. Tobacco use is the most common risk factor, accounting for about 50 percent of bladder cancer, Grossman says.
To conduct the study, a sample of urine collected from the patients was divided in half, and one part was used for the NMP22 test. The rest was used for a cytology test, which is the screening method physicians traditionally use. The cytology test looks for abnormal cells in the urine and must be sent to outside laboratories for evaluation. Patients may wait as long as a week to receive these results, according to Grossman, while the results of the NMP22 test can be read within 30 to 50 minutes in the doctor's office.
The patients also received a cystoscopy, which uses a flexible endoscope to examine the bladder. This low-risk procedure can be performed under local anesthesia in a doctor's office and is considered the "gold standard" of diagnostic tests, but can fail to detect some bladder cancers, says Grossman.
In this study, the researchers looked at the sensitivity as well as the specificity of cytology versus the NMP22 test. Sensitivity refers to how frequently the test picked up the existence of cancer; specificity refers to whether the test detected cancer that truly existed, and not false positives.
Although NMP22 was more sensitive in this study, cytology was more specific (99 percent versus 86 percent), meaning that the number of false positives was higher for the NMP22 test. Still, the authors say "the high specificity of cytology is offset by low sensitivity, ambiguous test results, expense, and time lag to obtain reports."
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