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External Validation of the Renal Ablation-Specific (MC)2 Risk Scoring System in Predicting Complications from Percutaneous Renal Cryoablation



The (MC)2 score is a renal ablation-specific risk scoring system to predict major complications from percutaneous renal cryoablation (PRCA). However, it is untested in an external population of patients. The purpose of this study is to validate the ability of the (MC)2 score to predict major complications after PRCA in an external population.

Materials and Methods

Retrospective review of patients who underwent PRCA from 2004 to 2019. Patient demographics, medical histories, and tumor characteristics were collected. The (MC)2 score was calculated and patients were assigned to low risk (< 5), moderate risk (5–8) and high-risk (> 8) groups. Complications were recorded. Major complications were classified according to CIRSE guidelines.


Two hundred and one patients [M = 116; F = 85; median age = 65 (range 27–90)] met inclusion criteria. Eleven patients (5.5%) developed major complications and 50 patients (24.9%) developed minor complications. Of patients with major complications, mean tumor diameter was 39 mm (± 10.4), seven patients (63.6%) had a central tumor, four patients (36.4%) had complicated diabetes, and one patient (9.1%) had a prior MI. Major complication rates were 2.1%, 14%, and 14.3% in the (MC)2 low risk, moderate risk, and high risk groups, respectively. The mean (MC)2 score for patients with major complications [6.2 (± 2.4)] was higher than the mean score for patients with minor complications [4.7 (± 2.4) (p = 0.07)] and no complications [3.9 (± 1.9) (p < 0.01)]. The area under the ROC curve to predict major complications was 0.78.


The (MC)2 risk scoring system appropriately identifies patients at risk for major complications from PRCA in this external patient population.

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Correspondence to Benjamin J. McCafferty.

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Dr. Gunn is speaker and consultant for Boston Scientific, a speaker for Terumo, a consultant for Varian, and receives research support from Penumbra. None of the other authors report a potential conflict of interest associated with this work and there is no grant support associated with this work.

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McCafferty, B.J., Huang, J.J., El Khudari, H. et al. External Validation of the Renal Ablation-Specific (MC)2 Risk Scoring System in Predicting Complications from Percutaneous Renal Cryoablation. Cardiovasc Intervent Radiol (2021).

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  • Cryoablation
  • Risk stratification
  • Renal cell carcinoma
  • (MC)2 score