Laboratory Investigation
Dual-Energy CT–Derived Volumetric Iodine Concentration for the Assessment of Therapeutic Response after Microwave Ablation in a Rabbit Model with Intrahepatic VX2 Tumor

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Abstract

Purpose

To evaluate whether changes in volumetric iodine concentration (VIC) could serve as a suitable predictor of therapeutic response to microwave (MW) ablation in a rabbit intrahepatic VX2 tumor model.

Materials and Methods

Sixteen intrahepatic VX2 tumors were transplanted in 8 New Zealand White rabbits treated with MW ablation. Contrast-enhanced dual-energy CT scans were obtained at baseline and follow-up. Therapeutic response assessment by modified Response Evaluation Criteria In Solid Tumors (mRECIST), Choi criteria, and VIC changes was performed. An intraclass correlation coefficient (ICC) was used to characterize consistency of assessment results among the criteria used. Technical success was evaluated with explant pathologic findings as a reference. Correlations between technical success and variations in diameter, CT density, and VIC were analyzed.

Results

Disease control was observed in 4, 8, and 10 of the 16 tumors per mRECIST, Choi criteria, and VIC changes, respectively. VIC exhibited strong consistency (ICC = 0.807, P < .0001) with Choi criteria. According to explant pathology, technical success was achieved in 10 of the 16 tumors. There was a moderate correlation between VIC changes and technical success (r = 0.532, P = .034), and no correlation was found between technical success and variations in diameter or CT density.

Conclusions

Compared with mRECIST and Choi criteria, dual-energy CT–derived VIC allowed for better prediction of therapeutic response after MW ablation and could provide a potential imaging biomarker of tumor response to MW ablation in patients with hepatocellular carcinoma.

Section snippets

Animal Care

All experiments were approved by the animal care committee of our institution and performed in compliance with institutional guidelines. Ten male New Zealand White rabbits (aged 3–4 mo, weighing 2–2.5 kg; purchased from the department of laboratory animals of the study institution) were used in the study. The rabbits were housed in individual cages under controlled laboratory conditions with a temperature of 22°C ± 1 and air humidity of 55%. The lights were on for 12 hours every day, and the

Quantitative Response Assessment Measurement

The diameter of the viable tumor, CT density, and VIC at baseline and follow-up are shown in Table 2. The tumor diameters were significantly increased (P = .010). The mean CT density and mean VIC decreased from baseline to follow-up, but not significantly (P = .051 and P = .238, respectively).

Comparison of Different Evaluation Results

The results of response assessment using the different criteria are shown in Table 3. The disease control rate was significantly higher with the use of VIC changes versus mRECIST (P = .033). No significant

Discussion

The present study showed that dual-energy CT–derived VIC change is the imaging assessment method that more closely replicated pathologic findings after MW ablation compared with mRECIST and Choi criteria. VIC showed a better correlation with technical success than diameter or CT density did, and has the potential to be a better tumor response biomarker for MW ablation in patients with HCC.

A previous study (23) showed that volumetric iodine uptake could be used in assessing tumor response to

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  • L.Z. and N.W. contributed equally to this work.

    X.D. and B.F. contributed equally to this work.

    None of the authors have identified a conflict of interest.

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