Intermediate- and long-term oncological outcomes of active surveillance for localized renal masses: a systematic review and quantitative analysis

Objective: To evaluate intermediate- and long-term oncological outcomes of active surveillance (AS) for localized renal masses (LRMs). Methods: This systematic literature review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement and registered on PROSPERO (CRD42021230416). Studies on AS for LRMs with at least 3 years' follow-up were eligible. Two review authors independently screened the literature, extracted data, and assessed risk of bias. The primary outcomes were metastasis rate, renal cell carcinoma (RCC)-specific mortality (RCC-SM) and all-cause mortality (ACM). Pooled estimates were obtained from random-effects models. Subgroup analyses were performed for small renal masses (SRMs; ≤4 cm) and non-SRMs (>4 cm). Results: We analysed 18 unique cohorts comprising 2066 patients. The pooled initial maximum tumour size was 2.8 cm (95% confidence interval [CI] 2.7–3.0) and the percutaneous biopsy rate was 28%. The pooled mean annual growth rate was 2.8 mm (95% CI 2.1–3.4). Within a pooled mean follow-up of 53 months, 2.1% (95% CI 1.0–3.6) of patients developed metastatic disease, 1.0% (95% CI 0.3–2.1) died from RCC and 22.6% (95% CI 15.8–30.2) died from any cause. For patients with SRMs (nine studies, n = 987), the pooled metastasis rate was 1.8% (95% CI 0.5–3.7), RCC-SM was 0.6% (95% CI 0–2.1), and ACM was 28.5% (95% CI 17.4–41.4). Across five studies reporting on outcomes of 239 patients with non-SRMs, the pooled metastasis rate was 5.1% (95% CI 0–17.3), RCC-SM was 2.1% (95% CI 0–8.9) and ACM was 29.1% (95% CI 13.6–47.3). This review is limited by non-standardized inclusion criteria, definitions and follow-up, data heterogeneity, limited patient numbers in sub-analyses and absence of high-quality studies. Conclusions: Active surveillance is a safe intermediate- and long-term management option for well-selected patients with LRMs, especially those with SRMs. Limited data are available for non-SRMs, but current evidence would support further evaluation of this approach in selected patients. It is not possible to draw definitive conclusions until more high-quality data become available.