SUO 2017: Long-term Active Surveillance of Cystic Renal Masses

Washington, DC ( Active surveillance (AS) is increasingly being considered for these entities, as their relatively indolent clinical course is better characterized. In this series, the authors provide their institutional evaluation of AS for cystic renal masses. 

In an 11-year period, consecutive patients referred for management of complex cysts (>= Boniak 2f) were included; patients required at least 6 months of diagnostic imaging follow-up until the patient was discharged, deceased, underwent surgery, or was lost to follow-up. Patients were excluded if they had greater than 2 complex cysts, immediately underwent surgery, or had pre-existing renal disorders. All imaging studies were re-evaluated and any stage change was reviewed with a blinded radiologist. Interesting, they sub classified the Bosniak 3 cohort into 2 groups: septated enhancing Bosniak cysts (3s) and Bosniak 3 cysts with cyst wall only nodularity (3n). 

For the 140 patients initially included, a total 1640 images were reviewed. After exclusions, there were 140 lesions identified in 106 patients. Median follow-up for all patients was 46 months [IQR 23, 65.5] and patients underwent median number of 7 [IQR 4,9] diagnostic scans.

On multivariable analysis, progression was determined by cysts that were nodular (HR 6.16 [2.58,14.72], p<0.00004). Cysts that were entirely endophytic were less likely to progress HR 0.21 [0.05,0.85], p=0.028). Interestingly, 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). There was no significant difference in growth rate between Bosniak 4 and non-Bosniak 4 lesions. No patients developed metastatic disease. 

Based on this, the authors concluded that classification of Bosniak 3 cysts into 3n and 3s better characterizes their clinical behavior. Diagnostic change among Bosniak 3s and 2f cysts is common, while Bosniak 3n cysts behave more like Bosniak 4s. 

Regardless, however, there was no metastasic spread in the entire cohort, including Bosniak 4 cysts. Despite the selection bias, this study confirms recently published results that complex cysts do very well on AS. However, they do add some novel data regarding the subclassification of Bosniak 3 cysts into Bosniak 3s and Bosniak 3n, which may help better determine clinical management in the future.

Limitations / Discussion Points:

1. Patients that underwent intervention up front (therefore selected for higher complexity or patient uncertainty) were excluded – this biases the cohort towards better outcomes in patients that were surveyed.

Presented by: Deepak Pruthi, MD, UT Health San Antonio

Co-Authors: Qianqian Liu, Iain Kirkpatrick, Jonathan Gelfond, Darrel Drachenberg
Affiliation: University of Manitoba, Winnipeg, Manitoba, Canada

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, twitter: @tchandra_uromd at the 18th Annual Meeting of the Society of Urologic Oncology, November 20-December 1, 2017 – Washington, DC