Cryoablation of bone metastases from renal cell carcinoma for local tumor control

Background: Patients with bone metastases from renal cell carcinoma often are not surgical candidates and have a poor prognosis. There are limited data on the use of cryoablation as a locoregional therapy for bone metastases. Our objective was to assess the local tumor-control rate following cryoablation of bone metastases in the setting of renal cell carcinoma. Methods: We retrospectively reviewed the medical records of patients with metastatic renal cell carcinoma who underwent cryoablation for bone metastases between 2007 and 2014. We excluded patients if the intent of treatment was for pain palliation only, if cryoablation was performed without an attempt for complete tumor control (cytoreduction), or if the patient had no further follow-up beyond the cryoablation procedure. We recorded patient demographics, procedural variables, and complications. Cross-sectional imaging and clinical follow-up were reviewed to determine disease recurrence. The median overall survival and recurrence-free survival were determined using the Kaplan-Meier method. Results: Forty patients (30 male and 10 female) with 50 bone metastases were included for analysis. The mean patient age was 62 years (range, 47 to 82 years). The median follow-up was 35 months (95% confidence interval [CI], 22.7 to 74.4 months). Twenty-five (62.5%) of the 40 patients had oligometastatic disease, defined as £5 metastases at the time of ablation. The mean tumor size was 3.4 ± 1.5 cm. Metastases in the pelvic region represented 68% of the treated tumors (34 of 50). The overall local tumor-control rate per lesion was 82% (41 of 50). Patients with oligometastatic disease experienced better local tumor control (96% [24 of 25]) compared with patients who had >5 metastases (53.3% [8 of 15]) (p = 0.001). The local tumor-control rate was better for lesions for which a larger mean difference between maximum iceball diameter and maximum lesion diameter was achieved (2.2 ± 0.9 cm for those without recurrence versus 1.35 ± 1.2 cm for those with recurrence; p = 0.005). There were 3 grade-3 complications and 1 grade-4 complication. Conclusions: Cryoablation can be effective for achieving local oncologic control in bone metastases from renal cell carcinoma and may represent a valuable alternative to surgical metastasectomy in select patients. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.