OBJECTIVE: To determine the risk factors associated with clinical outcome in patients with lymph node (LN)-positive urothelial carcinoma of the upper urinary tract (UTUC) treated with radical nephroureterectomy (RNU) and lymphadenectomy, focusing on the concept of LN density (LND). PATIENTS AND METHODS: Patients undergoing RNU with regional lymphadenectomy were identified through multi-institutional databases. All pathology slides were re-evaluated by genitourinary pathologists unaware of the clinical data. The exposure variable used was LND (continuously coded and that of all possible thresholds) with recurrence-free and disease-specific survival (DSS) serving as the outcome measures. RESULTS: Of 432 patients undergoing RNU with lymphadenectomy, 135 (31%) had LN metastases. Within a median follow-up of 4.1 years, 90 of the 135 patients with LN metastases (68%) had disease recurrence and 76 (58%) died from UTUC. The mean (sem) 5-year recurrence-free and DSS probabilities were 27 (4)% and 33 (5)%, respectively. The median (range) LND was 50 (3-100)%. The most informative threshold for LND in relation to outcome was 30%. In multivariable analyses that adjusted for the effects of tumour stage and grade, patients with a LND of ≥30% were at greater risk of both cancer recurrence, with 5-year rates of 25 (5)% vs 38 (8)% (hazard ratio 1.8, P = 0.021) and mortality, with 5-year rates of 30 (6)% vs 48 (9)% (1.7, P = 0.032) compared to those with a LND of <30%. Our results are primarily limited by a lack of standardization in the lymphadenectomy template. CONCLUSION: We evaluated the concept of LND for the first time in UTUC. LND provides additional prognostic information in patients with node-positive disease after RNU. The use of LND in clinical trials might provide an additional insight into the value of LN dissection in patients undergoing RNU.
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