Active Surveillance for Localized Renal Masses: Tumor Growth, Delayed Intervention Rates, and >5-yr Clinical Outcomes

Active surveillance (AS) has gained acceptance as a management strategy for localized renal masses.

To review our large single-center experience with AS.

From 2000 to 2016, we identified 457 patients with 544 lesions managed with AS from our prospectively maintained kidney cancer database. A subset analysis was performed for patients with ≥5-yr follow-up without delayed intervention (DI).

Linear growth rates (LGRs) were estimated using linear regression for the initial LGR (iLGR) AS interval and the entire AS period. Overall survival (OS) and cumulative incidence of DI were estimated with Kaplan-Meier methods utilizing iLGR groups, adjusting for covariates. DI was evaluated for association with OS in Cox models.

Median follow-up was 67 mo (interquartile range [IQR] 41-94 mo) for surviving patients. Cumulative incidence of DI (n=153) after 1, 2, 3, 4, and 5 yr was 9%, 22%, 29%, 35%, and 42%, respectively. Median initial maximum tumor dimension was 2.1cm (IQR 1.5-3.1cm). Median iLGR and overall LGR were 1.9 (IQR 0-7) and 1.9 (IQR 0.3-4.2) mm/yr, respectively. Compared with the no growth group, low iLGR (hazard ratio [HR] 1.25, 95% cumulative incidence [CI] 0.82-1.91), moderate iLGR (HR 2.1, 95% CI 1.31-3.36), and high iLGR (HR 1.87, 95% CI 1.23-2.84) were associated with DI (p=0.003). The iLGR was not associated with OS (p=0.8). DI was not associated with OS (HR 1.34, 95% CI 0.79-2.29, p=0.3). Five-year cancer-specific mortality (CSM) was 1.2% (95% CI 0.4-2.8%). Of 99 patients on AS without DI for >5 yr, one patient metastasized.

At >5 yr, AS±DI is a successful strategy in carefully managed patients. DI often occurs in the first 2-3 yr, becoming less likely over time. Rare metastasis and low CSM rates should reassure physicians that AS is safe in the intermediate to long term.

In this report, we looked at the outcomes of patients with kidney masses who elected to enroll in active surveillance rather than immediate surgery. We found that patients who need surgery are often identified early and those who remain on active surveillance become less likely to need surgery over time. We concluded that active surveillance with or without delayed surgery is a safe practice and that, when properly managed and followed, patients are unlikely to metastasize or die from kidney cancer.