The aim of the present study was to evaluate the safety and efficacy of computed tomography (CT)-guided percutaneous microwave ablation (MWA) of renal cell carcinoma (RCC) along with identifying prognostic factors affecting the progression survival rate. Institutional database retrospective research identified 69 patients with a biopsy proven solitary T1a (82.6%) or TIb (17.4%) RCC who have underwent percutaneous CT-guided MWA. Kaplan–Meier survival estimates for events were graphed and Cox regression analysis was conducted. Mean patient age was 70.4 ± 11.5 years. Mean size of the lesions was 3 ± 1.3 cm. Mean follow up time was 35.6 months (SD = 21.1). The mean progression free survival time from last ablation was 84.2 months. For T1a tumors, the cumulative progression free survival rate for 1, 6, 12 and 36 months were 100% (SE = 0%), 91.2% (SE = 3.7%), 91.2% (SE = 3.7%) and 87.5% (SE = 4.4%); the recurrence free survival rate for T1a RCC was 94.9%. For T1b tumors, the cumulative progression free survival rate for 1, 6, 12 and 36 months were 100% (SE = 0%), 63.6% (SE = 14.5%), 63.6% (SE = 14.5%) and 63.6% (SE = 14.5%). Grade 1 complications were recorded in 5 (7.2%) patients. Significantly greater hazard for progression was found in cases with a tumor size > 4 cm (HR = 9.09, p = 0.048). No statistically important difference regarding tumor progression was recorded between T1a tumors with a diameter ≤3 cm and >3 cm. In summary, the results of the present study show that CT guided percutaneous MWA is an effective technique for treatment of T1a renal cell carcinomas, irrespective of tumor size. T1b tumors were associated with higher progression rates.

To compare different parameters of the sphericity index of the ablation zone following microwave ablation (MWA) on cirrhotic- and healthy-liver parenchyma in a series of patients treated with the same MWA system. Institutional database research identified 46 patients (77 lesions) who underwent MWA. “Cirrhotic liver group” (CLG) included 35 hepatocellular carcinoma lesions; “healthy liver group” (HLG) included 42 metastatic lesions. The long axis (LAD), short axis 1 (SAD-1) and 2 (SAD-2), the mean SAD-1 and SAD-2 (mSAD) diameter (in mm) and the mean sphericity (mSPH) index of the ablation zones were evaluated for each treated lesion in both groups from baseline to follow-up. A mixed model analysis of variance reported significant main effect of group on SAD-1 (p = 0.023), SAD-2 (p = 0.010) and mSAD (p = 0.010), with HLG showing lower values compared to CLG. No differences were detected on the LAD (p_FDR = 0.089; d = 0.45), and mSPH (p_FDR = 0.148, d = 0.40) between the two groups. However, a significant main effect of time was found on LAD (p < 0.001), SAD-1 (p < 0.001), SAD-2 (p < 0.001) and mSAD (p < 0.001), with decreased values in all indices at follow-up compared to baseline. A significant group by time interaction was observed on mSPH (p = 0.044); HLG had significantly lower mSPH at follow-up where CLG did not show any significant change. Our findings indicate that although in cirrhotic liver short axis diameter of the MWA zone seems to be significantly longer, this has no effect on the sphericity index which showed no significant difference between cirrhotic vs. healthy liver lesions. On the contrary, on one month follow-up ablation zones tend to become significant more ellipsoid in healthy whilst remains stable in cirrhotic liver.