Assessing the impact of the absence of detrusor muscle in ta low-grade urothelial carcinoma of the bladder on recurrence-free survival

Background: Obtaining detrusor muscle (DM) in transurethral resection of bladder tumor (TURBt) specimen is considered a surrogate marker of resection quality. However, evidence was principally investigated in high-risk tumors. Therefore, DM sampling for low-grade (LG) urothelial carcinoma (UC) remains poorly investigated and certainly requires further investigation. Objective: To assess whether the absence of DM in TURBt specimen has a negative impact on recurrence-free survival (RFS) in patients with a Ta LG UC. Design, setting, and participants: A multicenter TURBt database was queried for "LG, Ta, UC of the bladder." All patients treated between 1996 and 2018 with tumor grade assessed according to both 1973 World Health Organization and 2004 WHO/International Society of Urological Pathology grading classifications and with a minimum follow-up of 1 yr were included. Patients with a previous history of high-grade UC, upper urinary tract UC, or bladder tumor differentiations other than UC were excluded. Intervention: TURBt. Outcome measurements and statistical analysis: Baseline demographic, clinical, and pathologic data were analyzed. The European Organization for Research and Treatment of Cancer (EORTC) risk group was recorded. Kaplan-Meier analysis was performed to assess the predictive role of clinical and pathologic data for RFS. Univariable and multivariable Cox regression analyses were performed to identify the predictors of recurrence. Results and limitations: Overall, 521 patients were included. At Kaplan-Meier analysis, the low-risk cohort displayed significantly higher RFS than the intermediate-risk cohort (1-yr RFS 87% vs 79%; log-rank p = 0.007). At univariable Cox regression analysis, only gender, multiple tumors, tumor diameter ≥3 cm, and EORTC risk group were significant predictors of recurrence. Absence of DM had no impact on RFS. Multivariable Cox regression analysis confirmed gender and EORTC risk group as independent predictors of recurrence. Conclusions: Absence of DM in TURBt specimen has negligible role in RFS of patients with Ta LG tumors of the bladder.