Skin-to-tumor Distance Predicts Treatment Failure of T1A Renal Cell Carcinoma Following Percutaneous Cryoablation

Objective To determine the impact of skin-to-tumor (STT) distance on the risk for treatment failure following percutaneous cryoablation (PCA). Methods We retrospectively reviewed patients who underwent PCA with documented T1a recurrent renal cell carcinoma (RCC) at 2 academic centers between 2005 and 2015. Patient demographics, tumor characteristics, and perioperative and postoperative course variables were collected. Additionally, we measured the STT distance by averaging the distance from the skin to the center of the tumor at 0°, 45°, and 90° on preoperative computed tomography imaging. Results We identified 86 patients with documented T1a RCC. The mean age at the time of surgery was 69 years (range: 37-91 years), and the mean tumor size was 2.7 cm (range: 1.0-4.0 cm). With a mean follow-up of 24 months (range: 3-63 months), 11 (12.8%) treatment failures occurred. Patients with treatment failure had significantly higher mean STT distance than those without: 11.0 cm (range: 6.3-20.1 cm) compared to 8.4 cm (range: 4.4-15.2 cm), respectively ( P  = .002). STT distance was an independent predictor of treatment failure (odds ratio: 1.32, 95% confidence interval: 1.04-1.69, P  = .029). STT distance greater than 10 cm had a fourfold increased risk of tumor treatment failure (odds ratio: 4.43, 95% confidence interval: 1.19-16.39, P  = .018). Tumor size, R.E.N.A.L. Nephrometry score, and number of cryoprobes placed were not associated with treatment failure. Conclusion STT, an easily measured preoperative variable, may inform the risk of RCC treatment failure following PCA.