Multicenter study of active surveillance for small renal masses: Real world practice pattern.

Introduction: Active surveillance (AS) is a safe strategy for small renal masses (SRM) suspicious of renal cell carcinoma. In this study we analyze real world outcomes of active surveillance SRM from 5 tertiary Spanish centers, assessing clinical, radiological, and pathological characteristics, as well as therapeutic options.

Methods: A multicenter retrospective review was conducted including patients on AS from January 2012 to September 2024. We analyzed the indication for AS, initial lesion size, growth rate (GR), and progression on active surveillance. Cox regression analysis was performed to identify predictor of deferred intervention (DI).

Results: A total of 384 patients with renal tumors were included in AS, with an initial mean tumor size of 20.5mm. With a mean follow-up period of 43 months, the average GR across the cohort was 1.4 mm/y. About 15% of patients (n = 59) received active treatment (partial nephrectomy 56%, radical nephrectomy 16%, and radiofrequency 28%). Age, tumor size and tumor growth were factors correlated with delayed intervention, and only initial tumor size was correlated with GR. Pathological analysis after active treatment showed high grade clear cell carcinoma in 43.5% of cases with a GR of > 5 mm/y, as compared to 19.4% of oncocytomas in slow growing lesions. No disease progression nor cancer-specific deaths were observed in our series.

Conclusions: In our multicenter cohort, AS is a valid option for SRMs without affecting oncological outcomes, with clinical factors such as age, tumor size, GR and initial biopsy influencing decisions on intervention.