T. Wittmann1, S. Best1, S. Wells1, T. Ziemlewicz1, J. L. Hinshaw1, M. Lubner1, F. Shi1, F. T. Lee1, S. Nakada1, E. J. Abel1 1University Of Wisconsin School Of Medicine And Public Health,Madison, WI, USA
Introduction: While surgery is the gold standard treatment for small (≤4cm) renal cell carcinoma (RCC), percutaneous cryoablation provides a nephron-sparing alternative that may also result in curative outcomes. In addition, the recent development of high-powered microwave ablation (MWA) may offer potential benefits over cryoablation. The objective of this study was to evaluate disease recurrence after treatment for patients with small RCC treated with ablation or surgery.
Methods: A total of 489 patients were treated with percutaneous ablation or surgery for localized RCC (confirmed with biopsy or surgical pathology) at our institution from 2001-2015. Differences in patient and disease characteristics among patient cohorts were evaluated using t-test or chi squared analysis.
Results: Of the 489 patients, 314 (64.2%) were treated surgically, 100 (20.4%) were treated using MWA and 75 (15.3%) had cryoablation. There was no difference in gender, race, body mass index, smoking history, R.E.N.A.L. nephrometry score, laterality, tumor diameter, or histologic RCC subtype among ablative treatments or surgery (p=0.13, 0.08, 0.08, 0.18, 0.16, 0.29, 0.80, 0.3).
Patients treated surgically were younger (p<0.0001) with median age 56.9 (IQR 48-66) compared to MWA (median age 67.0 IQR 59-72) or cryoablation (median age 65, IQR 60-74). Patients treated surgically were also more likely to have symptoms at presentation (p=0.01) compared to ablative treatments and more likely to have higher nuclear grade compared to ablative treatments (0.0002). Median Charlson Comorbidity Index was 2 (IQR 1-3) in surgically treated patients, compared to 3 (IQR 2-4) and 3 (IQR 2-4) in MWA and cryoablation respectively (p<0.0001).
Median follow-up was 9 months (IQR 6-18) for patients treated with MWA compared to 40 months (IQR 24-60) for cryoablation and 41 months (IQR 15-80) for surgery (p<0.0001).
Local recurrence was identified in 11(14.7%) patients following cryoablation compared to 1(1%) patients following MWA or 3(1%) after surgery, (p<0.0001). Development of metastatic RCC was observed in 2 (2.7%), 0 (0%), and 12 (3.8%) of patients following cryoablation, MWA or surgery respectively, (p=0.13).
Conclusion: Local recurrence is rare after surgery or percutaneous microwave ablation for small localized RCC. Cryoablation is associated with higher rates of local recurrence and retreatment compared to surgery. Future studies with longer follow-up are necessary to determine whether local recurrence rates are superior after treatment with MWA compared to cryoablation.