Accuracy of cross-sectional imaging in predicting tumor viability using the LI-RADS treatment response algorithm after image-guided percutaneous ablation with radiologic-pathologic explant correlation.

BACKGROUND

Accurate assessment of viable HCC on pre-transplant cross sectional imaging is important for correct organ allocation and overall patient outcome following liver transplantation.

PURPOSE

Determine accuracy of LI-RADS TRA compared to explant pathology in patients treated with thermal ablation, using contrast enhanced multiphase CT and MRI.

MATERIALS AND METHODS

Imaging studies for 119 consecutive adult HCC patients treated with thermal ablation and liver transplantation from March 2001 to September 2019 at a single tertiary care hospital were retrospectively studied by three Board-certified radiologists. LI-RADS TRA categories for each tumor were compared with explant pathology. Cohens Kappa test and inter-reader agreement by Fleiss κ test, with 95% confidence intervals obtained with bootstrap technique were used.

RESULTS

Of the 119 patients (median age 59 years, 95 [80%] male) with 165 HCCs treated with percutaneous thermal ablation, 68% were completely necrotic and 32% were viable on pathologic analysis. Tumors viable on explant were larger on pre-treatment imaging (median 2.4 vs. 2.1 cm; p = 0.02) with no difference in pre-transplant ablation cavity sizes between groups (4.0 vs. 3.9 cm, respectively; p = 0.58). NPV of LI-RADS TRA for viable tumor was 71% (68-74); PPV of 62.5% (39-81) (p = 0.01) with a sensitivity of 19% (9.4-32), specificity of 95% (89-98), and accuracy of 70% (63-77). On explant, 55 incidental treatment naïve viable tumors, not visible on pre-transplant imaging, were found in 33 patients.

CONCLUSION

The "non-viable" category of LI-RADS TRA even when applied to a relatively uniform percutaneous ablation cohort, demonstrated low sensitivity in predicting absence of viable tumor. MRI had more accuracy than CT in predicting tumor viability when compared to explant pathology.