Predictors of Delayed Intervention for Patients on Active Surveillance for Small Renal Masses: Does Renal Mass Biopsy Influence Our Decision?

Objective To review our clinical T1a renal mass active surveillance (AS) cohort to determine whether renal mass biopsy was associated with maintenance of AS. Materials and Methods From our prospectively maintained database we identified patients starting AS from June 2009 to December 2011 who had at least 5 months of radiologic follow-up, unless limited by unexpected death or delayed intervention. The primary outcome was delayed intervention. Clinical, radiologic, and pathologic variables were compared. We constructed Kaplan-Meier survival curves for maintenance of AS. Cox multivariable regression analysis was performed to assess predictors of delayed intervention. Results We identified 118 patients who met criteria for inclusion with a median radiologic follow-up of 29.5 months. The delayed intervention group had greater initial mass size and faster growth rate compared to those who continued AS. Rate of renal mass biopsy was similar between the 2 groups. In the multivariable analysis, size >2 cm (hazard ratio [HR] 3.65, 95% confidence interval [CI] 1.28-10.38, P  = .015), growth rate (continuous by mm/year: HR 1.26, 95% CI 1.12-1.41, P P  = .29), were associated with increased risk of delayed intervention. Time-to-event curves also showed that size was closely associated with delayed intervention whereas renal mass biopsy was not. Conclusion At our institution, growth rate and initial tumor size appear to be more influential than renal mass biopsy results in determining delayed intervention after a period of AS. Further analysis is required to determine the role of renal biopsy in the management of patients being considered for AS.