9p21 index as estimated by dual-color fluorescence in situ hybridization is useful to predict urothelial carcinoma recurrence in bladder washing cytology.

Recent studies have shown that chromosome 9p21 locus is frequently deleted in the early stages of urothelial carcinogenesis. To study the predictive value of the 9p21 aberrations in recurrence of urothelial carcinoma of the urinary bladder, we applied dual-color fluorescence in situ hybridization for 9p21 and chromosome 9 centromere to the bladder washing cytology samples that were obtained from the patients with urothelial carcinoma of the urinary bladder treated by transurethral resection. For the evaluation, the 9p21 index was defined as the ratio of the mean number of 9p21 signals per nucleus for that of the chromosome 9 centromere signals per nucleus in each of the bladder washing cytology samples. The 9p21 index values of the bladder washing cytology samples with no (G0) cytologic atypia were significantly higher than those of the bladder washing cytology samples with moderate (G2) (P < .01) and severe (G3) (P < .001) cytologic atypia, but the index values did not statistically differ from those of the bladder washing cytology samples with mild (G1) cytologic atypia. Recurrence-free survival in the patients with a low 9p21 index value (<0.9) was significantly poorer in comparison with the patients with a high 9p21 index value (>0.9). Furthermore, 2 patients of bladder washing cytology G1 with a low 9p21 index value recurred much sooner than the other patients of the bladder washing cytology G1 category. These findings indicate that a decreased 9p21 index value is associated with recurrence of urothelial carcinoma of the urinary bladder, and the 9p21 index may be useful as a marker to identify patients with elevated risk of recurrence of urothelial carcinoma of the urinary bladder.