Imaging of the Liver Following Interventional Therapy for Hepatic Neoplasms

Predicting early necrosis of colorectal liver metastases using volumetric enhancement on baseline MRI and oil deposition on post-cTACE unenhanced CT

PURPOSE

To predict tumor necrosis after conventional TACE (cTACE) in patients with colorectal liver metastasis (CRLM) based on volumetric oil deposition on CT one day after treatment.

METHODS

Thirty-four lesions in 20 men and 6 women were included in this IRB-approved HIPAA-compliant, retrospective lesion-by-lesion-based study. Semiautomatic volumetric segmentation of target lesions was performed on baseline MRI and post-treatment CT. Predicted percentage of tumor necrosis was defined as 100%-(%baseline MRI enhancement-%CT oil deposition). Necrosis on post-TACE MRI was measured after volumetric segmentation to assess the accuracy of predicting tumor necrosis. The relationship between predicted necrosis percent and post-cTACE measured necrosis percent on MRI was compared using Pearson correlation analysis. Inter-reader agreement was calculated by intraclass correlation coefficient (ICC) after using the same method.

RESULTS

Patients in this cohort had a mean age of 64 ± 14 years. Mean percentage of the viable tumor on pre-cTACE venous phase MRI was 58.5% ± 23.9%. Mean oil deposition was 19.8% ± 14.6%. Mean percentage of calculated necrosis one month after cTACE was 59.2% ± 22.7% on venous phase MRI, which had a significant correlation with predicted necrotic percentage of 61.3% ± 19.3% (r = 0.89, p < 0.0001). ICC for enhancement percentage on pre-cTACE and post-cTACE venous phase MRIs were 0.93 (95% CI 0.83, 0.97) and 0.86 (95% CI 0.66, 0.94), respectively. ICC for oil deposition was 0.92 (95% CI 0.81, 0.96).

CONCLUSION

Measuring oil deposition of the whole tumor on CT one day after cTACE can assist to predict post-cTACE tumor necrosis.

Evolution of Radioembolization in Treatment of Hepatocellular Carcinoma: A Pictorial Review

Transarterial radioembolization (TARE) with yttrium 90 has increasingly been performed to treat hepatocellular carcinoma (HCC). TARE was historically used as a palliative lobar therapy for patients with advanced HCC beyond surgical options, ablation, or transarterial chemoembolization, but recent advancements have led to its application across the Barcelona Clinic Liver Cancer staging paradigm. Newer techniques, termed radiation lobectomy and radiation segmentectomy, are being performed before liver resection to facilitate hypertrophy of the future liver remnant, before liver transplant to bridge or downstage to transplant, or as a definite curative treatment. Imaging assessment of therapeutic response to TARE is challenging as the intent of TARE is to deliver local high-dose radiation to tumors through microembolic microspheres, preserving blood flow to promote radiation injury to the tumor. Because of the microembolic nature, early imaging assessment after TARE cannot rely solely on changes in size. Knowledge of the evolving methods of TARE along with the tools to assess posttreatment imaging and response is essential to optimize TARE as a therapeutic option for patients with HCC. ^©RSNA, 2021.

Evaluation of Hepatocellular Carcinoma Treatment Response After Locoregional Therapy

Locoregional therapy (LRT) for hepatocellular carcinoma can be used alone or with other treatment modalities to reduce rates of progression, improve survival, or act as a bridge to cure. As the use of LRT expands, so too has the need for systems to evaluate treatment response, such as the World Health Organization and modified Response Evaluation Criteria In Solid Tumors systems and more recently, the Liver Imaging Reporting and Data System (LI-RADS) treatment response algorithm (TRA). Early validation results for LI-RADS TRA have been promising, and as research accrues, the TRA is expected to evolve in the near future.

Post Locoregional Therapy Treatment Imaging in Hepatocellular Carcinoma Patients: A Literature-based Review

Imaging plays a crucial role in the diagnosis of hepatocellular carcinoma (HCC) as well as in determining treatment efficacy, or complications, following therapy. Unlike other cancers, HCC is most commonly treated by locoregional therapies (LRTs) such as thermal ablation, transarterial chemoembolization, and transarterial radioembolization. These treatments can lead to changes on imaging that make determination of residual/recurrent disease difficult. This literature-based review discusses the expected postimaging findings following LRT.

Hepatic imaging following intra-arterial embolotherapy

PURPOSE

To discuss guidelines and salient imaging findings of solid tumors treated with common intra-arterial procedures used in interventional oncology.

METHODS

A meticulous literature search of PubMed-indexed articles was conducted. Key words included "imaging + embolization," "imaging + TACE," "imaging + radioembolization," "imaging + Y90," "mRECIST," and "EASL." Representative post-treatment cross-sectional images were obtained from past cases in this institution.

RESULTS

Intra-arterial therapy (IAT) in interventional oncology includes bland embolization, chemoembolization, and radioembolization. Solid tumors of the liver are the primary focus of these procedures. Cross-sectional CT and/or MR are the main modalities used to image tumors after treatment. Traditional size-based response criteria (WHO and RECIST) alone are of limited utility in determining response to IAT; tumoral necrosis and enhancement must be considered. Specifically for HCC, the EASL and mRECIST guidelines are becoming widely adopted response criteria to assess these factors. DWI, FDG-PET, and CEUS are modalities that play an adjunctive but controversial role.

CONCLUSIONS

Radiologists must be aware that the different forms of intra-arterial therapy yield characteristic findings on cross-sectional imaging. Knowledge of these findings is integral to accurate assessment of tumor response and progression.