Active Surveillance of Small Renal Masses in a Large Danish Cohort: Assessing Proficiency in Patient Selection.

Small renal masses (SRMs) are often benign or early-stage cancers with low metastatic potential. The risk of overtreating SRMs is a particular concern in elderly or comorbid patients, for whom the risks associated with active surveillance (AS) are lower than the risks of surgical management. The aim is to systematically analyse a large cohort of AS patients to provide valuable insights into patient selection and outcomes concerning delayed intervention (DI) and AS termination. We retrospectively analysed data from 563 AS patients across three institutions from 2012 to 2023. Patients were classified into three groups: those currently in AS (n=283), those who underwent DI (n=75), and those who terminated AS (n=205). DI patients were younger, and had larger initial tumour size and higher growth rates (GRs) than AS patients. A significant number of patients terminated their AS, mainly due to comorbidities and death from non-kidney cancer causes, suggesting unsuitability for initial AS enrolment. AS appears to be a safe initial management strategy for SRMs, with an overall low GR and only one patient developing metastasis. The patient selection for AS appears inconsistent, highlighting the need for improved criteria to identify AS candidates, especially considering comorbidities and the possibility of subsequent active treatment in the event of progression.