BACKGROUND AND OBJECTIVE: While active surveillance (AS) is an alternative to surgical interventions in patients with small renal masses (SRMs), evidence regarding its oncological efficacy is still debated. We aimed to evaluate oncological outcomes for patients with SRMs who underwent AS in comparison to surgical interventions. METHODS: In April 2024, PubMed, Scopus, and Web of Science were queried for comparative studies evaluating AS in patients with SRMs (PROSPERO: CRD42024530299). The primary outcomes were overall (OS) and cancer-specific survival (CSS). A random-effects model was used for quantitative analysis. KEY FINDINGS AND LIMITATIONS: We identified eight eligible studies (three prospective, four retrospective, and one study based on Surveillance, Epidemiology and End Results [SEER] data) involving 4947 patients. Pooling of data with the SEER data set revealed significantly higher OS rates for patients receiving surgical interventions (hazard ratio [HR] 0.73; p = 0.007), especially partial nephrectomy (PN; HR 0.62; p < 0.001). However, in a sensitivity analysis excluding the SEER data set there was no significant difference in OS between AS and surgical interventions overall (HR 0.84; p = 0.3), but the PN subgroup had longer OS than the AS group (HR 0.6; p = 0.002). Only the study based on the SEER data set showed a significant difference in CSS. The main limitations include selection bias in retrospective studies, and classification of interventions in the SEER database study. CONCLUSIONS AND CLINICAL IMPLICATIONS: Patients treated with AS had similar OS to those who underwent surgery or ablation, although caution is needed in interpreting the data owing to the potential for selection bias and variability in AS protocols. Our review reinforces the need for personalized shared decision-making to identify patients with SRMs who are most likely to benefit from AS. PATIENT SUMMARY: For well-selected patients with a small kidney mass suspicious for cancer, active surveillance seems to be a safe alternative to surgery, with similar overall survival. However, the evidence is still limited and more studies are needed to help in identifying the best candidates for active surveillance.

Cancer Prognostics and Health Outcomes Unit University of Montreal Health Centre Montreal Canada

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; 2nd Department of Urology Centre of Postgraduate Medical Education Warsaw Poland

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Collegium Medicum Faculty of Medicine WSB University Dąbrowa Górnicza Poland

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Biomedical Sciences Humanitas University Pieve Emanuele Italy

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Jikei University School of Medicine Tokyo Japan

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama Japan

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Semmelweis University Budapest Hungary

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Shariati Hospital Tehran University of Medical Sciences Tehran Iran

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Shimane University Faculty of Medicine Shimane Japan

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology Shimane University Faculty of Medicine Shimane Japan; Department of Urology Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama Japan

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology University Medical Center Hamburg Eppendorf Hamburg Germany

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Department of Urology University of Texas Southwestern Medical Center Dallas TX USA; Department of Urology Weill Cornell Medical College New York NY USA; Department of Urology 2nd Faculty of Medicine Charles University Prague Czechia; Division of Urology Department of Special Surgery The University of Jordan Amman Jordan; Karl Landsteiner Institute of Urology and Andrology Vienna Austria; Department of Urology Semmelweis University Budapest Hungary; Research Center for Evidence Medicine Urology Department Tabriz University of Medical Sciences Tabriz Iran

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Institute for Urology and Reproductive Health Sechenov University Moscow Russia

Department of Urology Comprehensive Cancer Center Medical University of Vienna Vienna Austria; Unit of Oncologic Minimally Invasive Urology and Andrology Department of Experimental and Clinical Medicine Careggi Hospital University of Florence Florence Italy

Department of Urology Okayama University Graduate School of Medicine Dentistry and Pharmaceutical Sciences Okayama Japan

Unit of Urological Robotic Surgery and Renal Transplantation Careggi Hospital University of Florence Florence Italy; Department of Experimental and Clinical Medicine University of Florence Florence Italy; European Association of Urology Young Academic Urologists Renal Cancer Working Group Arnhem The Netherlands

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