The Impact of Fluorescence in situ Hybridization on the Staging of Upper Tract Urothelial Carcinoma

<b><i>Objectives:</i></b> The aim of the study was to evaluate the impact of fluorescence in situ hybridization (FISH) diagnostics on the T stage in final histology specimen of patients undergoing radical nephroureterectomy (RNU) due to upper tract urothelial carcinoma (UTUC) at a large tertiary care center. <b><i>Methods:</i></b> We retrospectively analyzed patients who underwent RNU at our center between 2008 and 2020. Inclusion criteria were RNU due to UTUC. Urine cytologies were used for FISH analysis to detect chromosomal abnormalities. Pre-FISH group was defined as patients without access to routine preoperative urinary FISH testing (2008–2014), and FISH group was defined as patients with access to routine FISH testing. Primary outcome was T stage in final histology. Statistical analysis was performed by χ² test and Mann-Whitney <i>U</i> test. <b><i>Results:</i></b> Out of 212 patients who underwent RNU at our center between 2008 and 2020, 155 patients were included into the final analysis. The median age was 71 (range 33–90) years, and 108 (69.7%) patients were male and 47 (30.3%) female. Age and gender were not differently distributed in both groups (age: <i>p</i> = 0.925; gender: <i>p</i> = 0.682). Organ-confined disease was found in 37/72 patients in the pre-FISH cohort and in 48/83 patients in the FISH cohort (<i>p</i> = 0.422). Within organ-confined disease, 18/37 patients revealed a T stage smaller than T1 in the pre-FISH cohort and 35/48 patients in the FISH cohort (<i>p</i> = 0.022). <b><i>Conclusions:</i></b> Preoperative FISH diagnostics add important information to preoperative diagnostic workup of patients with UTUC. Within organ-confined disease, a significant shift toward T stages lower than T1 is observed. Further research is required to determine the impact of this shift on survival in UTUC.