Survival Outcomes of Patients with Treated vs Actively Surveilled Bosniak III or IV Kidney Cysts: A Systematic Review.

Background and objective: Bosniak III and IV kidney cysts have high malignancy rates, and treatment is often recommended. However, evidence suggests active surveillance (AS) may achieve similar cancer-specific survival (CSS) and overall survival (OS). We systematically reviewed studies comparing AS and treatment outcomes for these cysts. Methods: We searched Ovid MEDLINE, Ovid Embase, Scopus, and Web of Science to identify studies in English reporting CSS or OS outcomes for patients with Bosniak III or IV kidney cysts. Risk of bias was assessed with the Quality in Prognosis Studies tool. The Grading of Recommendations Assessment, Development, and Evaluation approach was used to provide a certainty of evidence summary. Per-study estimates were reported. Key findings and limitations: Five retrospective studies met the inclusion criteria. Across studies of Bosniak III cysts, 5-yr CSS was consistently >98% in both treated and AS cohorts, with several studies reporting no cancer-specific deaths among cases managed with AS. Studies of Bosniak IV cysts also had 5-yr CSS that exceeded 93% for both treatment strategies, including cohorts with 100% CSS in selected AS patients. OS was reported inconsistently and tended to be lower in AS cohorts with Bosniak III cysts, reflecting differences in baseline age, comorbidity burden, and competing causes of mortality rather than true differences in oncologic treatment. All studies were retrospective and nonrandomized, with moderate to high levels of selection bias and confounding. Conclusion and clinical implications: AS may be an appropriate management strategy for carefully selected patients with Bosniak III and IV cysts.