Small renal masses progressing to metastases under active surveillance

Abstract

Purpose We conducted a systematic review and pooled analysis of small renal masses under active surveillance to identify progression risk and characteristics associated with metastases. Materials and Methods A MEDLINE search was performed to identify all clinical series reporting surveillance of localized renal masses. For studies reporting individual level data, clinical and radiographic characteristics of tumors without progression were compared to those progressing to metastases. Results 18 series (880 patients, 936 masses) met screening criteria from which 18 patients progressing to metastasis were identified (mean 40.2 months). Six studies (259 patients, 284 masses) provided individual level data for pooled analysis. With a mean follow up of 33.5±22.6 months, mean initial tumor diameter was 2.3±1.3 cm and mean linear growth rate was 0.31±0.38 cm/year. 65 masses (23%) exhibited zero net growth under surveillance; of which none progressed to metastasis. Pooled analysis revealed increased age (75.1±9.1 vs. 66.6±12.3 years, p=0.03), initial tumor diameter (4.1±2.1 vs. 2.3±1.3 cm, p<0.0001), initial estimated tumor volume (66.3±100.0 vs. 15.1±60.3 cm3, p<0.0001), linear growth rate (0.8±0.65 vs. 0.3±0.4 cm/yr, p=0.0001), and volumetric growth rate (27.1±24.9 vs. 6.2±27.5 cm3/yr, p<0.0001) in the progression cohort. Conclusions A substantial proportion of small renal masses remain radiographically static following an initial period of active surveillance. Progression to metastases occurs in a small percentage of patients and is generally a late event. These results indicate that in patients with competing health risks, radiographic surveillance may be an acceptable initial approach with delayed intervention reserved for those exhibiting significant linear or volumetric growth.

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