Conditional Survival of Patients with Small Renal Masses Undergoing Active Surveillance

To determine conditional survival for patients with small renal masses (SRM) undergoing active surveillance (AS).

Patients were enrolled in a prospective AS protocol at our institution between May 2005 and January 2016. Patients with SRM ≤4cm with serial cross-sectional imaging available in-house for review were included. Overall survival (OS) was estimated using Kaplan-Meier method and modeled via Cox proportional hazards models. The primary end points analyzed were the conditional probability of survival and tumor growth over time. Landmark analysis was used to evaluate survival outcomes beyond the 2-year mark after the initial scan. The relative conditional survival of AS patients was compared to those undergoing partial nephrectomy (PN) using inverse probability of treatment weighting (IPTW).

A total of 272 patients were included in this analysis. Mean initial SRM size was 1.74 cm ± 0.77 and the mean mass size closest to the 2-year mark was 1.97 cm ± 0.83. The likelihood of continued survival to 5 years improved after the 2-year landmark. Patients with masses <3cm who survived the first 2-years on active surveillance had a 0.84-0.85 chance of surviving to 5 years, and if they survived 3 years, the probability of surviving to 5 years improved to 0.91. A slow tumor growth (beta: 0.12; p<0.001) with parallel growth rates were found for tumors <3cm. Patients on AS and those who underwent PN had similar OS for approximately 7 years, beyond which PN demonstrated a trend of lower risk of death compared to AS, (HR 0.57; p=0.07).

Conditional survival probability of patients with SRM <3cm on AS increases after 2 years. This information may prove useful to urologists and patients who are considering continuing AS vs intervention after the first 2 years on AS. This article is protected by copyright. All rights reserved.

BJU international. 2018 Jul 14 [Epub ahead of print]

Firas G Petros, Aradhana M Venkatesan, Diana Kaya, Chaan S Ng, Bryan M Fellman, Jose A Karam, Christopher G Wood, Surena F Matin

Department of Urology, The University of Texas MD Anderson Cancer Center, Houston, Texas., Department of Diagnostic Radiology, The University of Texas MD Anderson Cancer Center, Houston, Texas., Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas.