External validation of a simplified prognostic model for survival in patients with extrinsic malignant ureteral obstruction treated with tandem ureteral stents–a retrospective cohort study

Introduction: Prognostic models of survival can identify patients with extrinsic malignant ureteral obstruction who will benefit from long-term drainage as offered by tandem ureteral stents. The study aims to validate a simplified prognostic model published by Cordeiro et al. and to identify additional prognostic predictors in a cohort of patients drained solely with tandem ureteral stents. Methods: Medical records of consecutive patients who underwent drainage of malignant ureteral obstruction with tandem ureteral stents between 2007 and 2020 were reviewed retrospectively; patients with benign ureteral obstruction were excluded. Risk factors for survival included were: [1] the number of malignancy-related events (categorized as ≥4 and <4) and [2] the Eastern Cooperative Oncology Group Index (categorized as ≥2 and <2)]. Patients with ≥1 risk factor were grouped as intermediate-unfavorable risk and those without risk factors as favorable risk. The Kaplan–Meier and log-rank tests were used for survival analysis. Univariable and multivariable Cox regression analyses were used to identify predictors of outcome. Results: The study cohort consisted of 65 patients; the median age was 60 years (IQR 51–72). The median follow-up time from diagnosis of hydronephrosis was 51 months (IQR 38–64). Estimated probabilities of survival at 1 month, 6 months 1 year, and 2 years were 100%, 87%, 75% and 57%, respectively in the favorable risk group (n = 40), and in the intermediate-unfavorable risk group (n = 25), 96%, 72%, 52%, and 20%, respectively, (p =.003). On multivariable analysis, the presence of ≥4 malignancy-related events (HR = 2.04, 95% CI [1.07–3.86], p =.03) and lung metastasis (HR = 2.37, 95% CI [1.0–5.6], p =.05) were associated with shorter survival. Conclusions: Our findings validate the prognostic model published by Cordeiro et al. The model can be applied when counseling patients being considered for drainage with tandem ureteral stents.