Introduction

Small renal cell carcinomas (RCC) may be treated using percutaneous microwave ablation (MW) but few data are available to evaluate treatment for tumors 4 - 7 cm in size. The purpose of this study was to evaluate safety, feasibility, and oncologic efficacy for consecutive biopsy-proven clinical T1b RCC treated with MW ablation.

Methods

Thirty-five biopsy-proven cT1b RCC in 34 consecutive patients (19M/15F, median age 66, IQR: 62.5 - 66.0) from May 2012 and October 2016. Patient and procedural data were collected including body mass index (BMI), comorbidities, RENAL nephrometry score. Technical success was evaluated with immediate contrast enhanced post-procedural imaging. Local tumor progression, incidence of complications, and changes in renal function were assessed at follow-up. The Kaplan-Meier method was used for survival analysis.

Results

Median tumor diameter and nephrometry score were 4.5 cm (IQR: 4.2 - 5.1) and 8.0 (IQR: 8.0 - 9.0), respectively. Median Charlson Co-Morbidity Index was 5.0 (IQR: 4.0 - 7.0). Clear cell RCC histology represented 33/35 (94%) tumors (1 Chromophobe and 1 Papillary Type 2 RCC). There was no significant change in eGFR (p = 0.963). There were 5 (14.7%) high-grade (Clavien-Dindo III-IV) procedure-related complications. Post-operatively one patient developed urosepsis, one developed a urinoma requiring stent placement, and one developed a retroperitoneal hematoma. The remaining two complications were related to the anesthetic. Of 25 patients with follow-up imaging available, the median duration of imaging and clinical follow-up was 17.0 months (IQR = 8.5 - 26.0) and 20.7 months (IQR = 13.9 - 27.6), respectively. Immediate technical success was achieved for 33/35 (94%) tumors. There were 2 patients with difficulty visualizing residual enhancing tumor during initial ablation that required repeat ablation. Local tumor recurrence occurred in 1 (2.8%) patient at 26.3 months. The 3 treatment failures were successfully treated with salvage microwave ablation conferring a secondary efficacy of 100%. Estimated 3-yr local progression-free survival, cancer specific survival and overall survival were 83%, 100% and 76%, respectively.

Conclusions

Conclusion: Percutaneous MW ablation is feasible and safe for clinical T1b RCC. Long-term follow-up is needed to establish oncologic efficacy.

Funding

None