Purpose: To retrospectively evaluate solid renal tumor sizes before and after treatment with radiofrequency (RF) thermal ablation to assess for immediate changes on cross-sectional imaging.
Materials and methods: Medical records were retrospectively reviewed in consecutive patients who underwent percutaneous image-guided RF thermal ablation for solid renal tumors between December 12, 2000, and December 13, 2006. All patients underwent noncontrast computed tomography (CT) immediately before and after RF ablation. Maximum renal tumor diameters were measured before and after ablation. Statistical analysis of tumor sizes before and after ablation and change in tumor sizes was performed with the paired Student t test with confidence intervals calculated.
Results: Seventy-two renal tumors were treated with RF ablation in 66 patients (42 men, 24 women; mean age, 68.4 years; range, 25-88 y). Mean tumor sizes were 27.5 mm (range, 9.8-64.8 mm; 95% CI, 24.9-30.1 mm) before ablation and 22.1 mm (range, 5.3-67.3 mm; 95% CI, 19.4-24.8 mm) immediately after ablation. An average decrease in renal tumor size of 21% (range, -10% to 50%) was identified, with a mean tumor diameter decrease of 5.4 mm (P < .05; 95% CI, 4.4-6.4 mm). No relationship between size or location of tumors and percentage decrease in size after RF ablation was identified. Measurement of tumors on 1-month follow-up CT showed no appreciable change compared with immediate postprocedural measurements.
Conclusions: Renal tumors decrease in size immediately after treatment with RF thermal ablation. Immediate tumor involution after RF ablation should be anticipated and follow-up imaging studies should ideally be compared to a baseline tumor size measured as soon as possible after ablation.