Tumor Growth Kinetics and Oncologic Outcomes of Patients Undergoing Active Surveillance for Residual Renal Tumor following Percutaneous Thermal Ablation.

Purpose: To evaluate growth kinetics and oncologic outcomes of patients with renal tumors undergoing active surveillance (AS) for residual viable tumor following percutaneous ablation.

Materials And Methods: Following percutaneous thermal ablation, residual tumor was detected in 21/133 (16%) patients on initial follow-up imaging, and AS was undertaken in 17/21 (81%) patients. Initial tumor volumes and volumes after ablation were assessed from cross-sectional imaging to calculate volumetric growth rate (VGR) and volume doubling time (VDT) of residual tumor. The rate of metastasis, overall survival, and renal cell carcinoma (RCC)-specific survival were compared between patients in the AS group and in the routine follow up group of patients who did not have residual tumor.

Results: Median tumor volume prior to ablation, after first ablation, and at final follow-up were 25 cm(3), 6 cm(3), and 6 cm(3), respectively, in patients with residual tumor. Stable, mild, and moderate VGR occurred in 8/17 (47%), 4/17 (24%), and 5/17 (29%) cases, respectively. The 4 cases with fastest VDT underwent delayed intervention with ablation (n = 1) and nephrectomy (n = 3) without subsequent residual, recurrence, or metastasis. There was no significant difference in the rates of RCC metastasis, overall survival, or RCC-specific survival between AS and routine follow-up groups. Metastatic RCC and subsequent death occurred in 1 patient in the AS group, after the patient had refused offers for retreatment for local progression over 60.7 months of follow-up.

Conclusions: In cases when patients are not amenable to further intervention, AS of residual tumor may be an acceptable alternative and allows for successful delayed intervention when needed.