Potential of urinary biomarkers in early bladder cancer diagnosis.

Carcinoma of urinary bladder ranks among the top ten most common cancers worldwide. Approximately 80% of the disease is superficial (limited to mucosa and lamina propria) at the time of presentation. However, the majority of these tumors recur and 15-20% progress into muscle-invasive disease. Cystoscopic surveillance of the urinary bladder remains the standard of care to identify these recurrences on follow-up. Not only is this an invasive procedure, but the sensitivity of cystoscopy can be as low as 70%, so there can be up to 30% of tumors that are missed. Urinary cytology, with recognized limitations, has been used as an adjunct to this procedure, pending discovery of alternate urinary biomarkers. In the past decade there has been tremendous advancement in producing urinary biomarkers for urinary bladder cancer research, reflecting advancements in genomics and proteomics. An ideal biomarker should be able to replace cystoscopic examination and be cost effective. Unfortunately, most of the identified protein or molecular biomarkers have failed this test. This article critically appraises the status of these urinary biomarkers in urinary bladder cancer, in addition to highlighting some of the difficulties in this research area.