Rochester, NY--A point-of-care assay that measures the nuclear matrix protein NMP22 in urine significantly improves detection of recurrent bladder cancer when used with cystoscopy, according to a new study.
The study, published recently in JAMA (2006; 295:299-305), found that cystoscopy alone identified 91.3% of cancers, whereas the combination of cystoscopy and the NMP22 test (BladderChek, Matritech, Inc., Newton MA) detected 99% of cancers. The test is FDA-approved both as an aid in the initial diagnosis of bladder cancer and for surveillance.
The fifth most common malignancy, bladder cancer comes with a 50% to 90% chance of recurrence. The resulting need for frequent surveillance cystoscopies after the initial tumor resection tends to include supplemental cytology, which can pick up hidden or small tumors, according to Edward Messing, MD, a co-author of the JAMA study. However, the success of this traditional combination approach is hampered by inconsistencies.
The new study looked at subjects with a history of bladder cancer. The study, conducted between 2001 and 2002, included 23 academic, private practice, and hospital facilities in nine states.
Urine samples were collected from the 668 enrolled patients for analysis of the NMP22 protein and for cytology testing before they underwent follow-up cystoscopy.
Researchers reported that they found bladder cancer in 103 of the 668 patients. Cystoscopy alone identified 91.3% of the cancers (94/103; 95% CI, 84.1%-95.9%). The combination of cystoscopy with the NMP22 assay detected 99% of the cancers (102/103; CI, 94.7%-100%; p=.005), and the NMP22 assay detected eight of nine cancers missed by cystoscopy alone. Seven of those tumors were high grade.
Sensitivity of the NMP22 test alone was 49.5% (51/103; 95% CI, 39.5%-59.5%). Its specificity was 87.8% (493/565; 95% CI, 84.2%-89.9%).
Cytology based on voided urine detected only three malignancies missed during initial cystoscopy and did not significantly increase the sensitivity of cystoscopy (94.2%; 95% CI, 87.7%-97.8%; p=.08). The NMP22-cystoscopy combination missed one low-grade tumor, according to Dr. Messing.
"The critical part here, which surprised me, was that of the nine tumors that the NMP22 BladderChek picked up, almost all were very high-grade and aggressive cancers," he said. "They were the kind of cancers where a significant delay in diagnosis may have been very dangerous for the patient."