Clinical utility of fluorescence in situ hybridization for prediction of residual tumor after transurethral resection of bladder urothelial carcinoma.

OBJECTIVES To evaluate the use of a multiprobe fluorescence in situ hybridization (FISH) assay for predicting the residual tumor load after transurethral resection (TUR) of bladder urothelial carcinoma (UC). METHODS Voided urine specimens were collected from 125 consecutive patients with suspected UC who had been admitted for TUR. Of the 125 patients, 89 with UC diagnosed underwent a second procedure (repeated TUR or cystectomy) 4-6 weeks after the initial TUR and were included in the present study. Using the pathologic findings from the second procedure, the patients were divided into those with (n = 38) and those without (n = 51) residual tumor. Urine samples were taken both before and after the initial TUR. The multiprobe FISH assay was performed to detect aneuploidy of chromosomes 3, 7, and 17 and the loss of the 9p21 locus. RESULTS Before the first TUR, no significant difference was found in the FISH-positive percentage between those with and without residual tumor. After the first TUR, the FISH-positive percentage in those with residual tumor was significantly greater than in those without residual tumor (42.2% vs 17.6%, P = .003). Moreover, before and after the initial TUR, the percentage of conversion from FISH positive to FISH negative in those with residual tumor was significantly lower than in those without residual tumor (28.9% vs 58.9%, P < .001). No patients were observed with a FISH result of conversion from negative to positive in those with and without residual tumor after the initial TUR. CONCLUSIONS FISH appears to be useful for the prediction of the presence of the residual tumor load after TUR of bladder UC.