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Friday, October 2, 2020

Intermediate to Long-Term Clinical Outcomes of Percutaneous Renal Masses Cryoablation

Intermediate to Long-Term Clinical Outcomes of Percutaneous Cryoablation for Renal Masses

Clinical question
What is the intermediate- and long-term efficacy and safety of percutaneous cryoablation (CA) in the treatment of renal masses?

Take-away point
CA is effective in treating renal masses with low rates of complications during the procedure and over intermediate- and long-term follow-up periods.

Knox J, Kohlbrenner R, Kolli K, et al. Intermediate to Long-Term Clinical Outcomes of Percutaneous Cryoablation for Renal Masses. J Vasc Interv Radiol. 2020;31(8):1242-1248.

Click here for abstract

Study design
Retrospective cohort study

Funding source
Self-funded or unfunded

Single institution, University of California San Francisco

Figure. Graph of overall survival (OS) Kaplan-Meier curve in patients with RCC


Procedural treatment of renal masses has classically been accomplished using partial or total nephrectomy. While newer percutaneous cryoablation (CA) and thermal ablation techniques have been shown to be safe and effective compared to surgery for T1 disease, there is a paucity of data on their intermediate- and long-term safety and efficacy.

In this study, the investigators sought to assess the intermediate- and long-term safety and efficacy of percutaneous CA for renal masses at a single institution. Patients who had undergone ablation with percutaneous CA for T1a or b renal masses were selected. Patients with multiple masses, history of prior nephrectomy, and inherited tumor syndromes were included. Outcomes included renal function pre- and post-procedure, intra- and post-procedure complications, local recurrence, new metastatic disease, or complete response. R.E.N.A.L. nephrectomy score, a metric evaluating renal mass complexity that was previously validated as a measure of 30-day nephrectomy morbidity, was also calculated for each renal cell carcinoma (RCC) mass.

277 patients, 297 renal masses, and 299 CA procedures were analyzed. 207 masses were <3 cm, 74 were between 3 and 4 cm, and 16 were greater than 4 cm. 22 patients underwent multiple ablations; 12 due to separate mass, 7 due to incomplete initial ablation, and 3 due to recurrence. 46 patients had a history of prior renal surgery before CA. 4 patients had a known underlying genetic disease associated with their renal masses. 234 masses were confirmed RCC, 40 had nondiagnostic biopsies, and 8 had no biopsy results. 15 were biopsied at time of CA but were later found to be benign. Of the 234 RCC tumors, there were 93 (39.7%), 114 (50.8%), and 27 (11.5%) low-, intermediate-, and high-nephrectomy scoring masses respectively. There was no significant difference between pre-and 1-day post-procedural eGFR, but eGFR declined an average of 2.4 mL/min/1.73 m2 from preprocedural values to 3-month follow-up. There was no difference in decline between patients with and without prior renal surgeries or between patients with or without history of contralateral nephrectomy.

12 major complications occurred in 9 procedures (3%) with none resulting in death or permanent disability. AKI requiring hospitalization occurred 5 times, with none of the patients requiring hemodialysis. One patient suffered a retroperitoneal hematoma requiring transfusion and one patient had a renal artery pseudoaneurysm treated with embolization. Additionally, single occurrences of hemothorax, NSTEMI, post-procedural pulmonary embolism, high fever, and traumatic bladder catheter placement were all noted. Major complications occurred at a higher mean age (73.1) compared to uncomplicated procedures (65.6) (p=0.03). Tumor characteristics and high nephrectomy score did not affect complication rate (p=0.97) but significantly more complications occurred in patients with history of prior renal surgery (p<0.05).

For the 199 patients with RCC masses and follow-up information, mean clinical and imaging follow-up length was 29.7 months and 27.4 months respectively. Complete response was achieved in 195 masses (95.6%) after one procedure and 200 (98%) after 2 procedures. Mean time to complete response was 4.2 months. Local recurrence was noted in 3 cases (1.5%). Mean time to recurrence was 42.9 months (19.9-76.9 mo.). There was no association between recurrence and specific RCC mass characteristics. Recurrence did occur more often in patients with history of prior renal surgery (p=0.03). 10 patients developed metastatic disease (5.2%) at a mean follow-up time of 38.3 months. Independent factors associated with metastatic progression or local recurrence included history of prior kidney surgery, increased mass size, and clear cell subtype.


In this cohort, CA was demonstrated to be a safe and effective treatment modality for patients with renal masses. It offered high response rates with low recurrence and metastatic progression, and had lower complication rates than previous partial nephrectomy studies. Noted decreases in eGFR at 3-month follow-up were unlikely clinically significant and were less than those reported for partial nephrectomy. Patients with prior kidney surgery were at higher risk of complications, local recurrence, or metastatic disease, consistent with prior studies. Additionally, patients who experienced metastatic progression had aggressive disease features, bilateral disease, or did not have complete response after their first ablation. This study is limited by its retrospective nature and single arm design. Future studies will prospectively compare partial nephrectomy and CA procedures over extended follow-up periods.

Post Author
Jared Edwards, MD
General Surgery Intern (PGY-1)
Department of General Surgery
Naval Medical Center San Diego, San Diego, CA


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