Urine cytology has been the primary laboratory method for diagnosing and monitoring UC for the past 50 years. Urine cytology has excellent specificity but poor sensitivity for the detection of UC.3 A survey of 20 published studies has shown that the sensitivity of urine cytology for grade 1,2, and 3 tumors over the past 20 years has been 21%, 53%, and 78%, respectively.3 The problem with false-negative urine cytology test results is that the patient's tumor, if not detected by cystoscopy either, will have 3 or more months to progress to a higher, potentially incurable state before it is detected. This is of particular concern for grade 3 UC, which inexorably progress if not removed or treated.
The suboptimal sensitivity of urine cytology has prompted investigators to develop new tests with improved sensitivity for UC detection. For the most part, assays for the detection of UC fall into one of three categories: morphologic tests, antigen-detection tests, and molecular tests. The only assay that uses cellular morphologic changes alone to determine whether cancer is present is urine cytology. Other assays such as Immunocyt and FISH use morphology as part of the assay but also utilize the detection of tumor-associated antigens or genetic alterations, respectively, as part of the detection method. Antigen-based assays such as the BTA stat test and NMP22 rely on the detection of antigens that are present at higher concentrations in the urine of patients with UC. Genetic assays such as MA, FISH, and DNA ploidy analysis by image or flow cytometry are based on the detection of genetic alterations in cells that strongly suggest the presence of UC or other tumors. Antigen-based tests often have statistically better sensitivity but worse specificity (approximately 70%) than urine cytology. False-positive results can occur with inflammatory states that lead to an increase in the concentration of the antigens that are being measured. The high false-positive rate for many of the antigen-based tests leads to the need for confirmatory cystoscopy to determine whether UC truly is present.
Molecular tests generally have high specificity and sensitivity but are more laborious than antigen-based assays. Molecular tests tend to have high specificity because the genetic alterations are generally specific for cancer and not found in normal or reactive cells. Reactive cells are nonneoplastic epithelial cells that exhibit atypical cytologic features due to the presence of inflammation, chemotherapy, or radiation.
Currently, there are no therapies that are directed to specific molecular targets in UC. However, therapeutic agents similar to Gleevec and Herceptin, which are used for patients with specific genetic alterations in chronic myel-ogenous leukemia (BCR/ABL translocation) and breast cancer (HER2/NEU amplification), respectively, will presumably become available for treatment of UC patients. When such agents become available, it will likely be important to evaluate the patient's tumor for the presence or absence of the genetic alteration that the drug targets.
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