Presentation Authors: Leo D. Dreyfuss*, Shane A. Wells, Sara L. Best, Timothy J. Ziemlewicz, Meghan G. Lubner, J. Louis Hinshaw, Fred T. Lee, Stephen Y. Nakada, E Jason Abel, Madison, WI
Introduction: The recommended frequency and intensity of imaging surveillance following percutaneous ablation of renal cell carcinoma (RCC) is variable among institutions. The purpose of this study was to evaluate patterns of post ablation RCC recurrence in patients treated with percutaneous microwave (MW) or cryoablation (CA).
Methods: Consecutive patients with non-metastatic clinical T1a pathologically confirmed RCC treated with MW or CA from 2001-2017 were included. RCC syndrome patients were excluded. Images were reviewed by abdominal radiologists experienced with thermal ablation. Surveillance included abdominal cross-sectional imaging and chest x-ray q3-6 months for 2 years and yearly thereafter. Local recurrences (LR) were defined radiographically as enhancing tumor within the ablation site following complete ablation.
Results: 299 patients with pathologically diagnosed pT1a RCC were treated with percutaneous ablation including 184 MW and 115 CA. Six patients treated with CA had repeat ablation for residual tumor. No patients with T1a treated with MW had initially incomplete ablation.Of 115 T1a RCC patients treated with CA, median (IQR) follow-up was 41 months (20-68). A total of 8 (6%) tumors recurred at a median (IQR) 24 months (15-35). LR were identified for 6 T1a RCC CA at 15, 16, 24, 33, 35 and 67 months. Of 184 patients with T1a RCC treated with MW, median (IQR) follow-up was 21 months (12-40). T1a LR following MW were identified in 8 (4%) patients at 9, 9, 11, 12, 17, 29, 32, and 49 months following ablation. Of all T1a tumors, 0/299 recurred from 0-6 months, 11 (4%) recurred between 6-20 months, 5 (2%) recurred between years 2-3, with 2 (1%) recurred > 4 years. 9 T1a LR were treated with repeat ablation (5 CA, 4 MW), 3 had surgery (2 CA, 1 MW) and 2 had surveillance alone. Distant metastasis was rare (2%). One T1a (MW) patient had metastasis to femur and spine at 16 months. One T1a (CA) patient and one T1a (MW) progressed to lung metastasis at 14 and 18 months. One T1a (MW) progressed to the liver at 20 months.
Conclusions: Surveillance for T1a RCC treated with percutaneous ablation should focus on imaging time points between 6-20 months, between 24-36 months, and >4 years after ablation to identify 100% of recurrences. Metastatic progression for T1a RCC treated with thermal ablation is rare.