Image-guided percutaneous renal cryoablation: preoperative risk factors for recurrence and complications.

Objective: To investigate the value of the R.E.N.A.L nephrometry scoring system in predicting treatment success for image-guided percutaneous cryoablation (PCA).

Patients And Methods: The study included 139 patients with renal masses treated with PCA. Preoperative computed tomography or magnetic resonance images were reviewed by a urology resident. The primary endpoint variable was incomplete treatment or tumour recurrence. R.E.N.A.L. scores were categorized into low (4-6), moderate (7-9), and high (10-12). Logistic regression analysis was conducted to predict tumour recurrence. Additional variables collected included age at surgery, American Society of Anesthesiologists score, lesion size, skin-to-tumour distance, skin-to-hilum distance, and number of treatment cryoprobes.

Results: At a median follow-up of 24 months, there were 10 tumour recurrences (six moderate and four high R.E.N.A.L. score categories). Nephrometry score and number of probes used were not associated with recurrence (odds ratio [OR] 1.02, P = 0.9 and P = 0.53, respectively). The tumour distances for patients with recurrence and no recurrence were 10.8 cm and 8.5 cm, respectively (P ≤ 0.05), the skin-to-tumour distance was associated with treatment failure (OR 1.24, P = 0.015); for each unit increase in the mean value, patients were 1.5 times more likely to have a tumour recurrence (95% confidence interval [CI] 1.04-1.72). The model that best predicted complications included the number of probes used (P = 0.002) and R.E.N.A.L. score (OR 1.35, P = 0.027). For each additional probe used, patients were twice as likely to have complications (OR 1.98, 95% CI 1.28-3.05). With each unit increase in R.E.N.A.L. score, patients were 1.5 times more likely to experience a complication (OR 1.49, 95% CI 1.05-2.11).

Conclusions: An increased skin-to-tumour distance is associated with a higher risk of treatment failure after PCA. Furthermore, an increase in both R.E.N.A.L nephrometry score and number of probes used was associated with an increased risk of complications after PCA. The R.E.N.A.L. nephrometry score as a measure of tumour complexity was not associated with tumour recurrence.