Detection of Bladder Cancer in Urine Sediments by a Novel Multicolor Fluorescence In Situ Hybridization (Quartet) Test

Abstract

Background: Bladder cancer is among the common human malignancies that show a heavy mutational load and copy number variations of numerous chromosomes, which makes them a target for diagnostic explorations.

Objective: We aimed to design a multicolor fluorescence in situ hybridization (FISH) test referred to as the quartet test for the detection of bladder cancer in urine.

Design, setting, and participants: We performed genome-wide copy number variation analysis on cohorts from the University of Texas MD Anderson Cancer Center (n=40) and The Cancer Genome Atlas (n=129), and identified the most frequently amplified chromosomal regions. These data were used to select four of the amplified regions to design a multicolor FISH test, referred to as the quartet test. Assay validation was performed on urine samples from 98 patients with bladder cancer: 56 with low-grade papillary, 42 with high-grade invasive disease, and 48 benign controls.

Intervention: The quartet test can be used in clinical practice for noninvasive detection of bladder cancer.

Outcome measurements and statistical analysis: We initially analyzed samples using a fraction of abnormal cell scores and then by the quantitative score, which included not only the proportion of cells with abnormal copy numbers, but also the proportion of cells with numbers of altered copies and degree of amplification. We used receiver operator characteristic (ROC) curves to identify cutoff values for the scores at which performances of sensitivity and specificity were maximized.

Results and limitations: The copy number status assessed by probes detected in voided urine reflected the amplification status of the primary tumor. An ROC curve summarizing the proportion of assayed cells with any abnormal copy numbers gave specificity of 93.8% and sensitivity of 78.6% using the proportion of cells with abnormal copy numbers. The quantitative score giving extra weight to cells with multiple simultaneous amplifications provided 95.8% specificity and 76.8% sensitivity. Both percentage of abnormal cells and quantitative scores were highly effective for assessing the grade of the tumor. The full spectrum of potential clinical applications was not explored in the current study, and further validation studies are needed.

Conclusions: The quartet test shows promising specificity and sensitivity results, but it requires validation on a larger multi-institutional cohort of samples.

Patient summary: The quartet test can be used for noninvasive detection of bladder cancer in voided urine. It can also be used to assess the grade of the tumor and tumor recurrence as well as post-treatment effects.

Keywords: Bladder tumor; Copy number variation; Fluorescence in situ hybridization.