Review for 10.1186/s12876-025-04025-4 (2025)

Title: Clinical significance of contrast extravasation on computed tomography immediately after
thermal ablation for hepatic tumors
Version: 2 Date: 09 Apr 2025
Reviewer's report:
This retrospective single-center study evaluates the clinical significance of contrast
extravasation observed on immediate post-ablation CT in 30 patients undergoing thermal
ablation for hepatic tumors. Key findings suggest that contrast extravasation is typically benign,
requiring conservative management unless involving extrahepatic arteries, where embolization
is effective. The authors report high local tumor progression-free survival (96.4% at 1 year)
and overall survival (95.2% at 2 years), supporting the safety of observational approaches.
While the study addresses a clinically relevant gap, several methodological limitations and
unacknowledged confounders temper the strength of its conclusions.
Major Comments
1. Sample Size and Generalizability
- The small cohort (30 patients, 6 undergoing angiography) limits statistical power and
generalizability. Larger, multicenter studies are needed to validate findings, particularly
regarding rare extrahepatic arterial bleeding (only 2 cases).
2. Retrospective Design and Selection Bias
- Retrospective data collection introduces potential bias, especially in selecting patients for
angiography based on subjective "hemodynamic instability." Standardized criteria (e.g., specific
blood pressure/heart rate thresholds) are lacking, risking inconsistent clinical decisions.
3. Heterogeneity of Ablation Modalities
- Combining RFA, MWA, and cryoablation obscures modality-specific risks. These techniques
differ in thermal profiles and complication rates; pooled analysis may mask important
distinctions.
4. Absence of a Control Group
- Without comparing outcomes to patients without contrast extravasation, the true clinical
significance of extravasation (e.g., impact on survival or recurrence) remains unclear.
5. Short Follow-Up Period
- A mean follow-up of 23.3 months is insufficient to assess long-term outcomes, particularly in
cancer patients where recurrence or mortality may manifest later.
Minor Comments
1. Definition of High-Risk Locations
- Clarify how proximity to structures like the diaphragm or gastrointestinal tract influences
bleeding risk. Examples or imaging correlations would enhance understanding.
2. Statistical Methods
- For small samples (e.g., hemoglobin/hematocrit comparisons in 28 patients), non-parametric
tests (Wilcoxon signed-rank) may be more appropriate than paired t-tests. Justify test selection.
3. Figure and Table Consistency
- Ensure all figures/tables are referenced correctly (e.g., Table 1 lists 32 tumors in 30 patients,
but the text states "total number of tumors was 32").
4. Terminology Clarification
- The conclusion states "contrast extravasation... not associated with treatment efficacy," but
LTPFS is a surrogate for efficacy. Explicitly link findings to clinical endpoints.
5. Integration with Prior Literature
- Highlight how this study advances knowledge beyond prior RFA-focused reports, particularly
by including MWA and cryoablation.
Unacknowledged Limitations
1. Unadjusted Confounders
- Tumor size, location, cirrhosis severity, and comorbidities may influence bleeding risk and
outcomes but were not adjusted for in analyses.
2. CT Timing and Protocol Variability
- The interval between ablation and CT, as well as contrast administration protocols, could affect
extravasation detection. Standardization details are missing.
3. Operator Expertise
- Interventional radiologists' experience may impact complication rates and embolization
success. This variable is unaddressed.
4. Ethical Considerations
- While IRB approval was obtained, clarify if any patients were excluded due to incomplete data
and how this might bias results.