Related Experiment Video
Updated: Jul 7, 2025
Focal Laser Ablation of Prostate Cancer: An Office Procedure
Published on: March 30, 2021
Prospective Margin Estimates Predict Local Tumor Progression Following Microwave Ablation of Small Renal Masses
Franklin Iheanacho1, Nathaniel Rex1, Karim Oueidat2
1Department of Diagnostic Imaging, The Warren Alpert Medical School of Brown University, 593 Eddy Street, Providence, RI, 02903, USA.
Purpose:
To evaluate the relationship between prospectively generated ablative margin estimates and local tumor progression (LTP) among patients undergoing microwave ablation (MWA) of small renal masses (SRMs).
Materials And Methods:
Between 2017 and 2020, patients who underwent MWA for SRM were retrospectively identified. During each procedure, segmented kidney and tumor shapes were coregistered with intraprocedural helical CT images obtained after microwave antenna placement. Predicted ablation zone shape and size were then overlaid onto the resultant model, and a model-to-model distance algorithm was employed to calculate multiple ablative margin estimates. LTP was modeled as a function of each margin estimate by hazard regression. Models were evaluated using hazard ratios and Akaike information criterion. Receiver operating characteristic curve area under the curve was also estimated using Harrell's and Uno's C indices (HI and UI, respectively).
Results:
One hundred and twenty-eight patients were evaluated (median age 72.1 years). Mean tumor diameter was 2.4 ± 0.9 cm. LTP was observed in nine (7%) patients. Analysis showed that decreased estimated margin size as measured by first quartile (Q1; 25th percentile), maximum, and average ablative margin metrics was significantly associated with risk of LTP. For every one millimeter increase in Q1, maximum, and mean ablative margin, the hazard of LTP increased 67% (HR: 1.67; 95% CI = 1.25-2.20, UI = 0.93, HI = 0.77), 32% (HR: 1.32; 95% CI 1.09-1.60; UI = 0.93; HI = 0.76), and 48% (HR: 1.48; 95% CI 1.18-1.85; UI = 0.83; HI = 0.75), respectively.
Conclusion:
Prospectively generated ablative margin estimates can be used to predict the risk of local tumor progression following microwave ablation of small renal masses. LEVEL OF EVIDENCE 3: Retrospective cohort study.
Insights
Smaller ablative margins after microwave ablation for small renal masses increase the risk of local tumor progression. This study demonstrates that margin size is a key predictor for treatment success in MWA of SRMs.
Area of Science:
- Urology
- Interventional Radiology
- Oncology
Background:
- Small renal masses (SRMs) are often treated with minimally invasive techniques like microwave ablation (MWA).
- Accurate assessment of the ablation zone is crucial for predicting treatment outcomes.
- Local tumor progression (LTP) remains a concern after MWA for SRMs.
Purpose of the Study:
- To investigate the association between prospectively estimated ablative margins and the risk of local tumor progression (LTP) in patients with SRMs treated with MWA.
- To determine if quantitative margin assessments can predict MWA treatment efficacy.
Main Methods:
- Retrospective analysis of 128 patients who underwent MWA for SRMs between 2017-2020.
- Intraprocedural CT imaging was used to create 3D models of the kidney, tumor, and predicted ablation zone.
- A model-to-model distance algorithm calculated various ablative margin estimates.
- Hazard regression analysis modeled LTP as a function of margin estimates.
Main Results:
- Nine (7%) patients experienced LTP.
- Decreased estimated ablative margin size (measured by Q1, maximum, and average) was significantly associated with an increased risk of LTP.
- Each 1 mm increase in Q1, maximum, and mean margin size correlated with a 67%, 32%, and 48% increase in LTP hazard, respectively.
Conclusions:
- Prospectively generated ablative margin estimates are valuable predictors of LTP risk following MWA for SRMs.
- Quantitative margin assessment can aid in evaluating treatment effectiveness and guiding follow-up strategies.
- This retrospective cohort study (Level of Evidence 3) highlights the importance of margin size in MWA outcomes.
