A Systematic Review and Meta-analysis of Oncological Outcomes of Treated and Untreated Complex Cystic Renal Masses

Complex cystic renal masses, classified using the Bosniak system, pose diagnostic and therapeutic challenges due to their variable malignant potential. This systematic review and meta-analysis aimed to assess oncological outcomes in patients with cystic renal masses managed with active surveillance (AS) or active treatment (AT), and to report transitions from AS to AT.

A systematic literature search was conducted in MEDLINE, Embase, and Cochrane Library up to October 2024, following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Studies reporting oncological outcomes for Bosniak IIF-IV lesions were included. Eligible patients were those managed with AS or AT; most studies were retrospective observational cohort studies. Outcomes included recurrence, metastasis, cancer-specific mortality (CSM), overall survival, and transitions from AS to AT. Data were pooled using a random-effect model. Study quality and risk of bias were assessed using the Quality In Prognosis Studies tool.

Twenty-eight studies comprising 4,175 patients were included. Of 2353 patients managed with AS, 8.3% transitioned to AT after a mean of 20.5 mo. The 5-yr recurrence rate was 3.0% (95% confidence interval [CI]: 1.0-5.0); 5-yr CSM rate was 1.0% (95% CI: 0.1-2.0). The metastasis-free survival rate was 99.6% at 5 yr in AS patients and 97.5% at 10 yr in treated patients. No new metastases were reported beyond 10 yr. Histology revealed that 26% of the resected lesions were benign. Limitations include study heterogeneity, retrospective design, and a lack of randomised comparisons.

While individualised care remains essential, AS appears to be a safe initial strategy for selected patients with cystic renal masses, particularly Bosniak IIF. These findings support reducing unnecessary surgeries and highlight the need for standardised surveillance protocols. Further prospective studies are warranted.