Cross-sectional analysis of indwelling ureteral stents in patients with malignant ureteral obstruction

To the Editor, We commend the efforts of Matsui et al.1 for their novel analysis of the degree of luminal obstruction in indwelling nonmetallic and metallic ureteral stents in patients with malignant ureteral obstruction (MUO) using the Primary Cancer Site (P), Laterality (La), Serum Creatinine (C), and Treatment (T) (PLaCT) classification system. Upon further reflection, our goal is to contribute to the discussion of the suitable treatment protocols for the MUO patient population by presenting our perspectives on this study. Although the treatment plan after ureteral stent placement was mentioned to be at the discretion of the attending physician, we are interested in learning more about the original location of the patients before the evaluation of ureteral stent failure (eg, the amount of patients admitted in the emergency department versus ambulatory settings), especially in relation the specific capabilities of the various multicenter university hospitals in which the patients were seen. This information would help elucidate the urgent or nonurgent setting in which the grade 1 to grade 4 clinical obstruction and clinical nonobstruction occurred, necessitating the replacement of the stent as detailed in Table 21. Similarly, during the study period from March 2020 to March 2024, we would like to know how many patients with enrolled stents presented with an acute illness (eg, fever, sepsis, and urosepsis) during the study duration. Such a clarification would assist in identifying the precise number of acutely managed patients who were excluded from the study versus those included in the 1-, 3-, and 6-month evaluation intervals for ureteral stent failure-free survival. Supplementary information compiled from the previously gathered clinical data, summarizing the hemodynamic status of each enrolled patient, could serve as an invaluable resource for the reader. We acknowledge the noteworthy findings in the intermediate PLaCT risk group, where the non-MUS that were clinically obstructed caused symptoms despite the lumen being preserved (ie, grade 1 or grade 2) in the majority of cases1. However, given that the mean age of the non-MUS group is about 65 years old, a timeline that documents the period from the original diagnosis of MUO requiring first ureteral stent insertion to the period of ureteral stent failure for each case would help to correlate the degree of luminal obstruction for the grade1 and grade 2 categories with how clinically relevant these cases are for attending physicians that are responsible for managing MUO. While a greater lumen patency was observed for metallic stents versus nonmetallic stents in the intermediate PLaCT risk group1, we are intrigued by the need to deepen our understanding regarding the management of patients who had an MUS as their first ureteral stent insertion. For cases where a significant amount of luminal obstruction was discovered (eg, grade 3 or grade 4) in a patient who previously received a metal stent, a comparison of how those patients would be evaluated using the current PLaCT risk classification score versus additional established criteria2 would be insightful. Granting the lumen patency grades, their clinical relevance is not always clearly contextualized. Specifically, it remains unclear at what threshold of luminal obstruction renal function is jeopardized or when urgent intervention is warranted. Further discussion of the functional consequences can help readers fully understand and interpret the results. Notwithstanding the number of stents and ureteral units reported in the study, it remains unclear whether clinical outcomes, such as survival and stent failure, were assessed on a per-patient or per-stent basis. This distinction is critical, particularly in cases of bilateral stent placement, as it may influence the interpretation of event rates and could potentially lead to overestimation if multiple stents from the same patient were treated as independent observations. Despite the PLaCT score providing a practical prognostic framework, it may not completely account for other important clinical variables, such as comorbidities or functional status, which are especially relevant in patients with complex or advanced disease. Therefore, information about how a washout period was conducted, or details regarding the crossover protocol from MUS failure to another form of urinary diversion, would also be welcome. Finally, we would like to have seen an addition to the baseline patient characteristics in the MUS and non-MUS groups in Table 11 to include all age range groups, from children to seniors. This categorization could both enhance our understanding of the specific patient population that benefited from MUS and non-MUS stent replacement and clarify the distribution of patients selected according to the study’s inclusion criteria.