Measurement of Urinary Protein Can Help Detect Recurrent Bladder Cancer

Measurement of a certain protein in urine can increase the ability to detect bladder cancer recurrence, with test results available during the patient's visit, according to a study in the January 18 issue of JAMA.

Bladder cancer is the fifth most common malignancy in the United States, according to background information in the article. In 2005, there were an estimated 63,210 new cases and more than 13,000 deaths. There are 500,000 patients in the United States with a history of bladder cancer, making its prevalence higher than that of lung cancer. The probability of recurrence ranges from 50 percent to 90 percent, depending on stage, grade, and number of primary tumors. Consequently, rigorous surveillance is advocated. A combination of methods is used to monitor patients at risk of recurrent bladder cancer because no single procedure is 100 percent sensitive. Cystoscopy (visual examination of the bladder with a medical instrument) is a standard approach but can fail to detect some bladder cancers. Cytologic (cell) analysis of urine frequently is used as an adjunctive test, but can have poor sensitivity and variability in interpreting results.

H. Barton Grossman, M.D., of the M. D. Anderson Cancer Center, Houston, and colleagues investigated the clinical utility of a noninvasive urine test, which can be used in the physician's office, for the protein NMP22, as an aid in detecting recurrent cancer in patients with a history of bladder cancer.

The researchers compared its usefulness with that of voided urine cytology, which must be analyzed in a clinical laboratory. The study, conducted from September 2001 to February 2002, included 23 academic, private practice, and hospital facilities in 9 U.S. states and enrolled 668 patients with a history of bladder cancer. Prior to undergoing cystoscopy, patients provided a urine sample for analysis of NMP22 protein and for cytology testing.

Bladder cancer was diagnosed in 103 patients. Cystoscopy alone identified 91.3 percent of the cancers. The combination of cystoscopy with the NMP22 assay detected 99.0 percent of the malignancies. The NMP22 assay detected 8 of 9 cancers that were not visualized during initial cystoscopy, including 7 that were high-grade. The sensitivity and specificity of the NMP22 test alone were 49.5 percent and 87.3 percent, respectively. Cytology based on voided urine detected only 3 of the malignancies missed during initial cystoscopy and did not significantly increase the sensitivity of cystoscopy (94.2 percent).

The authors conclude, "When combined with cystoscopy, the NMP22 test improves the detection of recurrence in patients with a history of bladder cancer."

(JAMA. 2006;295:299-305. Available pre-embargo to the media at http://www.jamamedia.org)