Long-term Surveillance of Complex Cystic Renal Masses & Heterogeneity of Bosniak 3 Lesions

To better characterize the frequency of Bosniak cyst class changes and identify predictors of change and progression. To determine the average growth rate of cysts and validate the safety of active surveillance.

Consecutive patients referred for management of complex cysts (>= Bosniak 2F) were included. All imaging studies were re-evaluated and any stage change was reviewed with a blinded genitourinary radiologist. Bosniak 3 cysts were sub-classified into septated enhancing Bosniak cysts (3s) and cysts with wall or septation-only nodularity (3n). Multivariate Cox proportional hazards model identified predictors Bosniak classification change. Kaplan-Meier (KM) curves analyzed Bosniak cyst progression/regression.

A total 140 lesions were included and necessitated a review of 1011 abdominal scans in the 111 patients. Median follow-up was 46 months [IQR 23, 65.5] and patients underwent a mean 6.8 diagnostic scans. On multivariate analysis nodular cysts progressed (Hazard ratio (HR) 6.16 [2.58,14.72], p<0.00004) and entirely endophytic cysts were less likely to progress HR 0.21 [0.05,0.85], p=0.028). On KM analysis Bosniak 3s cysts were more likely to regress (p=0.0178) while Bosniak 3n cysts were more likely to progress than 3s cysts (p=0.0002). The growth rate of 3n cysts was 0.19cm/year (p=0.0493) and 2F cysts was 0.11cm/year (p=0.0327). No patients developed locally advanced or metastatic disease.

Diagnostic change among Bosniak 3s and 2F cysts is common; Bosniak 3n cysts behave more like Bosniak 4. Most complex kidney cysts can be safely monitored without intervention and the interval between serial imaging should be increased.

The Journal of urology. 2018 Aug 01 [Epub ahead of print]

Deepak K Pruthi, Qianqian Liu, Iain D C Kirkpatrick, Jonathan Gelfond, Darrel E Drachenberg

Department of Urology, University of Texas Health San Antonio. Electronic address: ., Department of Biostatistics, University of Texas Health San Antonio., Department of Diagnostic Radiology, University of Manitoba., Department of Urology, University of Manitoba.