Active surveillance of renal masses: an analysis of growth kinetics and clinical outcomes stratified by radiological characteristics at diagnosis

ABSTRACT

AIMS To determine the growth rate of renal masses (RMs) under active surveillance (AS), and to describe the clinical outcome of AS patients. Materials and Methods We conducted a retrospective review of an AS database to obtain demographics, radiological and pathologic characteristics and RM size of patients. RMs were followed at 6-12 month intervals for ≥1 year with computed tomography (CT), magnetic resonance imaging (MRI), or renal ultrasound. Kaplan-Meier analysis determined the annual likelihood of intervention. RMs were divided into 3 radiographic subcategories (solid, cystic, and angiomyolipoma). A linear regression model determined RM growth rates. Results 131 RMs in 114 patients were included. Median age, Charlson Comorbidity Index score and mean follow-up were 69.1 years, 4.0 and 4.2±2.6 years, respectively. Maximal tumor diameter (MTD) at diagnosis was 2.1±1.3 cm. 49 RMs exhibited negative or zero net growth. Mean MTD growth rate for all RMs was 0.72±3.2 (95% CI 0.16-1.28) mm/year. When stratified by MTD at diagnosis, mean RM growth rates were 0.84, 0.84, 0.44, 0.74 and 0.71 mm/year for RMs <1 cm, 1-<2cm, 2-<3cm, 3-<4cm and ≥4cm, respectively (p<0.01). The 5 and 10-year freedom from intervention rates were 93.1% and 88.5%, respectively. There was a single case of suspected metastases, but no deaths related to kidney cancer. Conclusions RMs under AS grew slowly, and had a low incidence of requiring surgical intervention and progression. Solid enhancing masses grew slowly, and were more likely to trigger intervention. AS should be considered for selected patients with small RMs. .