Long-Term Clinical Outcomes Following Radiofrequency and Microwave Ablation of Renal Cell Carcinoma at a Single VA Medical Center

https://doi.org/10.1067/j.cpradiol.2017.05.006Get rights and content

Purpose

Microwave ablation (MWA) is a relatively newer treatment modality for treatment of renal cell carcinoma (RCC), and only a few small studies have examined the short- and long-term outcomes for MWA applied to renal tumors. The purpose of this retrospective review is to assess the initial experience including technical short- and long-term success rates of using radiofrequency ablation (RFA) and MWA for RCC at a single Veterans Affairs (VA) medical center.

Materials and Methods

Tumor characteristics were recorded using the R.E.N.A.L. nephrometry score. Group comparisons were performed by using univariate logistic regression analysis to determine factors affecting primary treatment success, failure, and effectiveness. Kaplan-Meier local tumor progression-free survival following ablation was calculated.

Results

MWA and RFA groups were not significantly different in primary treatment success (P = 0.82). MWA primary treatment success (90.2%) was not associated with R.E.N.A.L criteria, whereas primary success in the RFA group (88.2%) was predicted by smaller tumor size (P = 0.002). Primary treatment effectiveness rates were not significantly different in MWA (88.2%) and RFA (80.3%) groups (P = 0.29). Although overall primary technique effectiveness was associated with size (P = 0.02), univariate analysis showed a significant association between tumor size and primary effectiveness for RFA (P = 0.002) but not MWA. There was no significant association between R.E.N.A.L score or criteria and primary treatment effectiveness in the RFA or MWA groups.

Conclusion

RFA and MWA both represent effective treatment modalities for RCC; larger tumor size may be associated with decreased efficacy of thermal ablation techniques.

Introduction

Open or laparoscopic partial nephrectomy, with a 97% 5-year recurrence-free survival, is considered the gold-standard treatment for renal cell carcinoma (RCC).1 Percutaneous treatments such as cryoablation (CRA) and radiofrequency ablation (RFA), however, have demonstrated 5-year survival rates (87%-89%) nearly approaching partial nephrectomy for stage T1a tumors.1, 2, 3, 4 Although each modality may have relative advantages and drawbacks, there are no data definitively favoring CRA or RFA for treatment of RCC.1

The relatively recent introduction of microwave ablation (MWA) adds yet another minimally invasive treatment option with specific potential treatment advantages. Potential advantages of MWA over RFA include reduced sensitivity to heat-sink effects and the ability to create larger, more uniform ablation zones compared to RFA.5 These same attributes, however, may also introduce increased theoretical risk to adjacent vascular structures, organs, and the renal collecting sytem.6 Importantly, the intermediate and long-term outcomes of MWA for RCC have not been extensively investigated.5 This retrospective study examines the short- and long-term treatment success and effectivness rates of RFA and MWA for RCC at a single Veterans Affairs (VA) medical center.

Section snippets

Study Cohort

We performed a retrospective analysis of each patient receiving RFA and MWA for biopsy-proven or presumed RCC by imaging at a single large VA medical center. Institutional review board approval was received for conducting this study. The study cohort included patients treated with percutaneous thermal ablation for RCC between January 2007 and December 2014. Inclusion criteria included (1) patients with biopsy-proven RCC or imaging findings and clinical presentation typical of RCC, (2) dedicated

Results

A total of 71 patients with 78 renal lesions underwent ablation (Fig. 1, Fig. 2, Fig. 3, Fig. 4). Further, 61 and 17 lesions were treated with RFA and MWA, respectively; 53.8% of lesions were biopsied before ablation; and 51% of all lesions were biopsy-proven RCC. MWA and RFA groups were not statistically different in R.E.N.A.L. parameters, patient demographics, tumor size, or tumor histopathology. Mean follow-up time for RFA (41 months) was significantly longer than MWA (12 months) (P <

Discussion

The R.E.N.A.L. nephrometry score is a reproducible scoring system of renal lesion complexity that has been validated in the surgical literature as a useful guide for surgical approach for renal lesion resection and predictor of treatment success and complications following surgery.3, 8 More recently, it has been shown that the R.E.N.A.L. nephrometry score, or at least specific components of the nephrometry score including tumor diameter and distance from the hilum, may be useful for predicting

Main Points

  • RFA and MWA both represent effective treatment modalities for T1a RCC.

  • Correlation of outcomes following ablation of renal tumors using a nephrometry score in future large studies with long-term follow-up may yield additional insight into tumor parameters associated with treatment failure or recurrence risk.

  • Larger tumor size may be associated with the lower treatment effectiveness.

References (11)

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Prior presentation/publications: These data were presented as an oral presentation in the same name at 2015 RSNA.

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