Researchers at 23 clinical sites, led by The University of Texas M. D. Anderson Cancer Center, enrolled 668 patients with a history of bladder cancer in a prospective study to evaluate the effectiveness of the NMP22 assay for detecting recurrences of the disease. Each patient provided a urine sample, which was tested for the presence of the NMP22 protein using the tumor marker assay and urine cytology. Bladder examinations (cystoscopy) and biopsy were used to determine the presence of the disease. Recurrent bladder cancer was found in 103 participants. The NMP22 assay alone detected 49.5 percent of recurrences (51 out of 103) while urine cytology detected only 12.2 percent (12 out of 98).
H. Barton Grossman, M.D., professor in M. D. Anderson's Department of Urology and the study's principal investigator, sees the potential of this test to give patients, as well as their physicians, greater peace of mind.
"Many of our patients with bladder cancer live long after their disease is initially discovered and treated, but the rate of recurrence is very high," Grossman says. "Current recommendations indicate lifelong screenings, at least once a year, to monitor their status. A test like the NMP22 assay which is accurate and easy to administer, I believe, will help identify and treat patients earlier when they a have better chance for a good outcome."
This study comes after an article last year in JAMA, also led by Grossman, found that the NMP22 assay was three times more effective than urine cytology for the initial diagnosis of bladder cancer for high-risk individuals.
The NMP22 assay works by detecting elevated amounts of the NMP22 protein in just a few drops of urine. The test does not require cancer cells to be present in urine. Test results can be read in the doctor's office in 30 to 50 minutes. With urine cytology, whole cells must be present in the urine, and the test must be performed in a laboratory. Results typically are available in about a week after a sample has been collected.
The study also reports that eight of the nine cases initially missed by cystoscopy were detected by the NMP22 assay; seven of these cases were classified as high-grade tumors. In this case, the NMP22 was significantly more sensitive than urine cytology, which only detected three of these cases.
While Grossman is optimistic about the benefits of the NMP22 assay, he cautions it still should be performed in conjunction with a cystoscopy, which is considered the "gold standard" for bladder cancer detection. A cystoscopy is a low-risk procedure using a flexible endoscope to view the walls of the bladder. It is performed under local anesthetic in a doctor's office.
The combination of the NMP22 assay with cystoscopy significantly increased the overall detection rate to 99 percent, compared with 91 percent for cystoscopy alone. Urine cytology combined with cystoscopy only increased detection to 94.2 percent in this study.
Bladder cancer is the fifth most common cancer in the United States. For the 500,000 Americans with a history of bladder cancer, the probability of recurrence can be as high as 50 percent depending on the stage, grade and number of primary tumors. Risk factors for the disease include a history of smoking, exposure to certain industrial chemicals and being over age 40. Hematuria, or blood in the urine is a warning sign of bladder cancer.
"Until we reach 100 percent for detection, there is always room for improvement," Grossman says, "but I think many patients could benefit from a test like this that helps detect tumors before they become advanced and require more aggressive treatment."
Co-authors of the study include Mark Soloway, M.D., University of Miami School of Medicine; Edward Messing, M.D., University of Rochester Medical Center; Giora Katz, M.D., Lake City Veterans Administration Hospital; Barry Stein, M.D., Rhode Island Hospital; Vahan Kassabian, M.D., Georgia Urology; and Yu Shen, Ph.D., M. D. Anderson.
Matritech, makers of the NMP22 assay, which is commercially known as BladderCheck, sponsored the study. The NMP22 assay is believed to be the only point-of-care test approved by the Food and Drug Administration for the initial diagnosis and surveillance of bladder cancer.