Response assessment of hepatocellular carcinoma treated with yttrium-90 radioembolization: inter-reader variability, comparison with 3D quantitative approach, and role in the prediction of clinical outcomes

DWI/ADC in response assessment after local-regional treatment of HCC - Pearls and Pitfalls

Many patients with hepatocellular carcinoma (HCC) present with advanced-stage disease or multifocal tumors which make them unsuitable for radical treatment options. In such cases, locoregional therapy (LRT) such as transarterial chemoembolization (TACE), transarterial radioembolization (TARE) can be used as a bridge to liver transplantation or to downstage borderline tumors. However, post treatment response assessment can be very difficult, especially in the case of TARE. The recently updated Liver Imaging Reporting and Data System treatment response algorithm (LI-RADS TRA) 2024 guidelines has included ancillary features of mild-moderate T2 signal intensity and diffusion restriction into the assessment algorithm. Diffusion-weighted imaging (DWI) would be particularly important in post-TARE assessment as early response assessment using traditional size and enhancement criteria can be challenging following TARE. However, the interpretation of restricted diffusion in post-treatment imaging can be challenging as DWI can be affected by various factors such as inflammatory changes, haemorrhage, or T2-relaxation time of the surrounding parenchyma. In this review article, we provide an overview of the advantages and challenges in the use of DWI to interpret treatment response after LRT.

Increased Voxel-Based Y90 Radioembolization Dose to Hepatocellular Carcinoma Improves Imaging Response

PURPOSE

To evaluate the relationship between radioembolization tumor dose and imaging response for hepatocellular carcinoma (HCC) treated with radioembolization.

MATERIALS AND METHODS

Retrospective single-institution evaluation of treatment-naïve patients with HCC who underwent TARE between November 2017 and September 2020. Dose-volume histograms (DVHs) were calculated from post 90Y single-photon emission computed tomography. Cross-sectional imaging was obtained at 3 months after radioembolization and evaluated by three blinded abdominal radiologists.

RESULTS

Forty-one patients underwent radioembolization who met the inclusion criteria. Median age was 67 years (range 41-84); 11 were female. At 3 months, 23/41 (56%) had complete response (CR), 9/41 (22%) had partial response (PR), and 8/41 (20%) had stable disease (SD) by mRECIST criteria. DVH analysis demonstrated that increased dose to different tumor volumes was predictive of a complete imaging response at 3 months (p < 0.05 for all). Receiver operating characteristic (ROC) analysis demonstrated a dose threshold of 687 Gy to 95% of the tumor volume resulted in the highest area under curve (AUC) at 0.86 (CI 0.73-0.95) and a positive predictive value (PPV) of 82% to predict complete response by mRECIST criteria.

CONCLUSION

Voxel-based dosimetry demonstrates that several dose thresholds are predictive of a complete imaging response by mRECIST criteria. A threshold dose of 687 Gy to at least 95% of the tumor volume led to the highest accuracy in predicting complete response by mRECIST criteria.

LEVEL OF EVIDENCE

Level 3, Cohort Study.

Prognostic value of early response in predicting survival in hepatocellular carcinoma patients treated with selective internal radiation therapy

OBJECTIVES

This study evaluates the prognostic value of tumor response on CT at 3 months, assessed by Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST (mRECIST), and Liver Imaging Reporting and Data System Treatment Response Algorithm (LR-TRA) in patients with hepatocellular carcinoma (HCC) treated with selective internal radiation therapy (SIRT).

MATERIALS AND METHODS

A retrospective analysis was conducted on 102 HCC patients treated with SIRT between 2018 and 2020. RECIST, mRECIST, and LR-TRA were assessed at 3 months post-SIRT. Overall survival (OS) and progression-free survival (PFS) were assessed using Kaplan-Meier analysis and Cox proportional-hazards models.

RESULTS

The median age was 71 years, and most patients (90%) had advanced-stage tumors (Barcelona Clinic Liver Cancer-C). After a median follow-up of 32.0 months (95% CI: 16.8-60.9), 60/102 patients died (59%), and 90/102 patients showed tumor progression (88%). Median OS was 20.4 months (95% CI: 15.4-33.0), and median PFS was 14.5 months (95% CI: 6.5-24.5); 1-year OS and PFS rates were 65.6% and 50.7%. Multivariable analysis revealed that early response according to RECIST 1.1 (HR 1.66, p = 0.30), mRECIST (HR 1.40, p = 0.215), and LR-TRA (HR 0.67, p = 0.30) were not predictors of OS. Disease progression evaluated by RECIST (HR 2.55, p < 0.001) and mRECIST (HR 2.53, p < 0.001), bilirubin levels (HR 1.03, p < 0.001), and prothrombin time (HR 0.98, p = 0.005) were predictors of OS. For PFS, neither RECIST nor mRECIST response, disease progression, nor LR-TRA viability were predictors.

CONCLUSION

In this advanced-stage HCC population, early response assessed by RECIST, mRECIST, and LR-TRA criteria did not predict OS or PFS after SIRT. However, early disease progression and liver function indicators were prognostic factors for OS.

KEY POINTS

QuestionHow well does early tumor response, assessed at 3 months post-selective internal radiation therapy (SIRT), predict survival in advanced hepatocellular carcinoma (HCC) patients? Findings Early response, assessed by RECIST, mRECIST, and LR-TRA, did not predict overall or progression-free survival; disease progression and liver function indicators were significant predictors. Clinical relevance This study highlights the limitations of early imaging criteria in predicting survival outcomes in advanced HCC post-SIRT, suggesting the need for alternative or complementary prognostic indicators to guide treatment decisions.

Temporal evolution of the LI-RADS radiation treatment response assessment on multiphase CT/MRI in patients undergoing selective internal radiation therapy for hepatocellular carcinoma

OBJECTIVES

To assess the temporal evolution and interobserver agreement of the early categories per the liver imaging reporting and data system (LI-RADS) radiation treatment response assessment (TRA) algorithm in patients receiving selective internal radiation therapy (SIRT) with Yttrium-90 for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

This single-center retrospective study included consecutive patients with treatment-naïve HCC who underwent serial contrast-enhanced CT/MRI before and after SIRT. Three masked radiologists independently evaluated response at 3-6 months. Another senior radiologist assessed response at 9, 12, 15, 18, 21, 24, and > 24 months after comprehensive review of available clinical-radiological information.

RESULTS

65 patients (mean age, 66.7 ± 11.2 years; 48 men) were included. At 3-6 months after SIRT, 47.7% (31/65) of lesions were assigned to the nonprogressing category, and the remaining 52.3% (34/65) to the nonviable category. Among early nonprogressing lesions, 64.5% (20/31) regressed to the nonviable category, 25.8% (8/31) remained nonprogressing, and 9.7% (3/31) evolved into the viable category at ≥ 12 months. The nonprogressing category decreased in number over time, with 61.3% (19/31) conversion to the nonviable category at 9 months. Among the early nonviable lesions, 91.2% (31/34) remained nonviable at ≥ 12 months, and 8.8% (3/34) evolved into the viable category. Agreement for the 3-6 months LR-TR category assignment was moderate (kappa = 0.46) with CT but almost perfect (kappa = 0.85) with MRI.

CONCLUSIONS

SIRT induced a delayed and sustained response in the majority of HCC patients after ≥ 12 months. MRI demonstrated superior agreement over CT in assessing response at 3-6 months.

KEY POINTS

Question Tumor response to SIRT can change; there is limited evidence on the evolution of the imaging appearance of HCC following SIRT. Findings Sixty-four and five-tenths of early nonprogressing lesions regressed to nonviable, and 91.2% of early nonviable lesions remained free of viability. LR-TR category assignment agreement was moderate with CT but almost perfect with MRI. Clinical relevance SIRT induced a delayed and sustained response in HCC, underscoring the necessity of dynamic evaluation of long-term changes in treated lesions. MRI with subtraction imaging may be preferred over CT for long-term monitoring, which may help prevent premature retreatment decisions.

Application of LI-RADS CT/MRI Radiation Treatment Response Assessment Version 2024: a study after transarterial radioembolization for hepatocellular carcinoma

PURPOSE

To compare the performance of the LI-RADS CT/MRI Radiation Treatment Response Assessment (TRA) version 2024 (v2024) after transarterial radioembolization (TARE) for hepatocellular carcinoma (HCC) with that of the LI-RADS CT/MRI TRA version 2017 (v2017).

METHODS

This retrospective study included patients with HCC treated with TARE followed by hepatic surgery between November 2012 and April 2023 at two tertiary referral centers. Each treated lesion was assigned an LI-RADS treatment response (LR-TR) category based on a consensus reading of three radiologists using both v2024 and v2017. The sensitivity and specificity of the two TRA versions were compared using the McNemar test, with histopathology as a reference standard.

RESULTS

A total of 46 (mean age, 56.2 years; 39 men) patients with 46 TARE-treated lesions (23 with incomplete [< 100%] necrosis) were included. The distribution of categories based on v2024 was as follows: LR-TR Nonviable, 52.2% (24/46); LR-TR Nonprogressing, 39.1% (18/46); and LR-TR Viable, 8.7% (4/46). While no category change was noted for LR-TR Nonviable lesions, 16 lesions classified as LR-TR Viable in v2017 were recategorized as LR-TR Nonprogressing in v2024. For predicting histopathologically incomplete necrosis, the LR-TR Viable or Nonprogressing categories of v2024 and the LR-TR Viable or Equivocal categories of v2017 showed equivalent high sensitivity (87.0%; 20/23; 95% confidence interval [CI]: 67.9, 95.5) and specificity (91.3%; 21/23; 95% CI 73.2, 97.6) (all P > 0.99).

CONCLUSION

While applying the updated radiation TRA v2024 resulted in recategorization, its diagnostic performance in predicting tumor viability was comparable to that of TRA v2017.

CT/MRI LI-RADS 2024 Update: Treatment Response Assessment

With the rising incidence of hepatocellular carcinoma, there has been increasing use of local-regional therapy (LRT) to downstage or bridge to transplant, for definitive treatment, and for palliation. The CT/MRI Liver Imaging Reporting and Data System (LI-RADS) Treatment Response Assessment (TRA) algorithm provides guidance for step-by-step tumor assessment after LRT and standardized reporting. Current evidence suggests that the algorithm performs well in the assessment of tumor response to arterial embolic and loco-ablative therapies and fair when assessing response to radiation-based therapies, with limited data to validate the latter. Both evidence-based and expert-based refinements of the algorithm are needed to improve its diagnostic accuracy after varying types of LRT. This review provides an overview of the challenges and limitations of the LI-RADS TRA algorithm version 2017 and discusses the refinements introduced in the updated 2024 LI-RADS algorithm for CT/MRI.

Early post-treatment MRI predicts long-term hepatocellular carcinoma response to radiation segmentectomy

OBJECTIVES

Radiation segmentectomy using yttrium-90 plays an emerging role in the management of early-stage HCC. However, the value of early post-treatment MRI for response assessment is uncertain. We assessed the value of response criteria obtained early after radiation segmentectomy in predicting long-term response in patients with HCC.

MATERIALS AND METHODS

Patients with HCC who underwent contrast-enhanced MRI before, early, and 12 months after radiation segmentectomy were included in this retrospective single-center study. Three independent radiologists reviewed images at baseline and 1st follow-up after radiation segmentectomy and assessed lesion-based response according to mRECIST, LI-RADS treatment response algorithm (TRA), and image subtraction. The endpoint was response at 12 months based on consensus readout of two separate radiologists. Diagnostic accuracy for predicting complete response (CR) at 12 months based on the 1st post-treatment MRI was calculated.

RESULTS

Eighty patients (M/F 60/20, mean age 67.7 years) with 80 HCCs were assessed (median size baseline, 1.8 cm [IQR, 1.4-2.9 cm]). At 12 months, 74 patients were classified as CR (92.5%), 5 as partial response (6.3%), and 1 as progressive disease (1.2%). Diagnostic accuracy for predicting CR was fair to good for all readers with excellent positive predictive value (PPV): mRECIST (range between 3 readers, accuracy: 0.763-0.825, PPV: 0.966-1), LI-RADS TRA (accuracy: 0.700-0.825, PPV: 0.983-1), and subtraction (accuracy: 0.775-0.825, PPV: 0.967-1), with no difference in accuracy between criteria (p range 0.053 to > 0.9).

CONCLUSION

mRECIST, LI-RADS TRA, and subtraction obtained on early post-treatment MRI show similar performance for predicting long-term response in patients with HCC treated with radiation segmentectomy.

CLINICAL RELEVANCE STATEMENT

Response assessment extracted from early post-treatment MRI after radiation segmentectomy predicts complete response in patients with HCC with high PPV (≥ 0.96).

KEY POINTS

• Early post-treatment response assessment on MRI predicts response in patients with HCC treated with radiation segmentectomy with fair to good accuracy and excellent positive predictive value. • There was no difference in diagnostic accuracy between mRECIST, LI-RADS, and subtraction for predicting HCC response to radiation segmentectomy.

Updates on LI-RADS Treatment Response Criteria for Hepatocellular Carcinoma: Focusing on MRI

As the incidence of hepatocellular carcinoma (HCC) and subsequent treatments with liver-directed therapies rise, the complexity of assessing lesion response has also increased. The Liver Imaging Reporting and Data Systems (LI-RADS) treatment response algorithm (LI-RADS TRA) was created to standardize the assessment of response after locoregional therapy (LRT) on contrast-enhanced CT or MRI. Originally created based on expert opinion, these guidelines are currently undergoing revision based on emerging evidence. While many studies support the use of LR-TRA for evaluation of HCC response after thermal ablation and intra-arterial embolic therapy, data suggest a need for refinements to improve assessment after radiation therapy. In this manuscript, we review expected MR imaging findings after different forms of LRT, clarify how to apply the current LI-RADS TRA by type of LRT, explore emerging literature on LI-RADS TRA, and highlight future updates to the algorithm. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 2.

Comparison of quantitative volumetric analysis and linear measurement for predicting the survival of Barcelona Clinic Liver Cancer 0- and A stage hepatocellular carcinoma after radiofrequency ablation

PURPOSE

The prognostic role of the tumor volume in patients with hepatocellular carcinoma (HCC) at the Barcelona Clinic Liver Cancer (BCLC) 0 and A stages remains unclear. This study aims to compare the volumetric measurement with linear measurement in early HCC burden profile and clarify the optimal cut-off value of the tumor volume.

METHODS

The consecutive patients diagnosed with HCC who underwent initial and curative-intent radiofrequency ablation (RFA) were included retrospectively. The segmentation was performed semi-automatically, and enhanced tumor volume (ETV) as well as total tumor volume (TTV) were obtained. The patients were categorized into high- and low-tumor burden groups according to various cutoff values derived from commonly used diameter values, X-tile software, and decision-tree analysis. The inter- and intra-reviewer agreements were measured using the intra-class correlation coefficient. Univariate and multivariate time-to-event Cox regression analyses were performed to identify the prognostic factors of overall survival.

RESULTS

A total of 73 patients with 81 lesions were analyzed in the whole cohort with a median follow-up of 31.0 (interquartile range: 16.0–36.3). In tumor segmentation, excellent consistency was observed in intra- and inter-reviewer assessments. There was a strong correlation between diameter-derived spherical volume and ETV as well as ETV and TTV. As opposed to all linear candidates and 4,188 mm3 (sphere equivalent to 2 cm in diameter), ETV >14,137 mm3 (sphere equivalent to 3 cm in diameter) or 23,000 mm3 (sphere equivalent to 3.5 cm in diameter) was identified as an independent risk factor of survival. Considering the value of hazard ratio and convenience to use, when ETV was at 23,000 mm3, it was regarded as the optimal volumetric cut-off value in differentiating survival risk.

CONCLUSION

The volumetric measurement outperforms linear measurement on tumor burden evaluation for survival stratification in patients at BCLC 0 and A stages HCC after RFA.

Modified quantitative and volumetric response evaluation criteria for patients with hepatocellular carcinoma after transarterial chemoembolization

Objective

This study aimed to investigate the cutoff value of quantitative and volumetric response evaluation criteria for patients with hepatocellular carcinoma (HCC) after transarterial chemoembolization (TACE) and compare the performance of the modified criteria to one-dimensional criteria in survival prediction.

Methods

A retrospective single-center study was performed for treatment-naive patients with HCC who underwent initial TACE between June 2015 and June 2019. Treatment response assessment was performed after the first observation by contrast CT or MRI, with the measurement of diameters by modified Response Evaluation Criteria in Solid Tumors (mRECIST) and volumes by quantitative European Association for Study of the Liver (qEASL). Overall survival (OS) was the primary endpoint of this study. The new cutoff value for volumetric response evaluation criteria was created using restricted cubic splines. The performance of modified qEASL (mqEASL, with the new cutoff value) and mRECIST on survival prediction was compared by Cox regression models in internal and external validation.

Results

A total of 129 patients (mean age, 60 years ± 11 [standard deviation]; 111 men) were included and divided into training (n=90) and validation (n=39) cohorts. The cutoff value for the viable volume reduction was set at 57.0%. The mqEASL enabled separation of non-responders and responders in terms of median OS (p<0.001), 11.2 months (95% CI, 8.5-17.2 months) vs. 31.5 months (95% CI, 25.5-44.0 months). Two multivariate models were developed with independent prognostic factors (tumor response, metastasis, portal vein tumor thrombus, and subsequent treatment) to predict OS. Model 2 (for mqEASL) had a greater Harrel's C index, higher time-dependent area under the receiving operator characteristic curve (AUROC), and more precise calibration on 6-month survival rates than Model 1 (for mRECIST).

Conclusions

With the modified cutoff value, the quantitative and volumetric response of HCC patients to TACE becomes a precise predictor of overall survival. Further studies are needed to verify this modification before application in clinical practice.

Assessment of HCC response to Yttrium-90 radioembolization with gadoxetate disodium MRI: correlation with histopathology

BACKGROUND AND AIMS

Transarterial ⁹⁰Y radioembolization (TARE) is increasingly being used for hepatocellular carcinoma (HCC) treatment. However, tumor response assessment after TARE may be challenging. We aimed to assess the diagnostic performance of gadoxetate disodium MRI for predicting complete pathologic necrosis (CPN) of HCC treated with TARE, using histopathology as the reference standard.

METHODS

This retrospective study included 48 patients (M/F: 36/12, mean age: 62 years) with HCC treated by TARE followed by surgery with gadoxetate disodium MRI within 90 days of surgery. Two radiologists evaluated tumor response using RECIST1.1, mRECIST, EASL, and LI-RADS-TR criteria and evaluated the percentage of necrosis on subtraction during late arterial, portal venous, and hepatobiliary phases (AP/PVP/HBP). Statistical analysis included inter-reader agreement, correlation between radiologic and pathologic percentage of necrosis, and prediction of CPN using logistic regression and ROC analyses.

RESULTS

Histopathology demonstrated 71 HCCs (2.8 ± 1.7 cm, range: 0.5-7.5 cm) including 42 with CPN, 22 with partial necrosis, and 7 without necrosis. EASL and percentage of tumor necrosis on subtraction at the AP/PVP were independent predictors of CPN (p = 0.02-0.03). Percentage of necrosis, mRECIST, EASL, and LI-RADS-TR had fair to good performance for diagnosing CPN (AUCs: 0.78 - 0.83), with a significant difference between subtraction and LI-RADS-TR for reader 2, and in specificity between subtraction and other criteria for both readers (p-range: 0.01-0.04). Radiologic percentage of necrosis was significantly correlated to histopathologic degree of tumor necrosis (r = 0.66 - 0.8, p < 0.001).

CONCLUSIONS

Percentage of tumor necrosis on subtraction and EASL criteria were significant independent predictors of CPN in HCC treated with TARE. Image subtraction should be considered for assessing HCC response to TARE when using MRI.

KEY POINTS

• Percentage of tumor necrosis on image subtraction and EASL criteria are significant independent predictors of complete pathologic necrosis in hepatocellular carcinoma treated with⁹⁰Y radioembolization. • Subtraction, mRECIST, EASL, and LI-RADS-TR have fair to good performance for diagnosing complete pathologic necrosis in hepatocellular carcinoma treated with⁹⁰Y radioembolization.

LI-RADS Treatment Response versus Modified RECIST for Diagnosing Viable Hepatocellular Carcinoma after Locoregional Therapy: A Systematic Review and Meta-Analysis of Comparative Studies

Purpose

To systematically compare the performance of liver imaging reporting and data system treatment response (LR-TR) with the modified Response Evaluation Criteria in Solid Tumors (mRECIST) for diagnosing viable hepatocellular carcinoma (HCC) treated with locoregional therapy (LRT).

Materials and Methods

Original studies of intra-individual comparisons between the diagnostic performance of LR-TR and mRECIST using dynamic contrast-enhanced CT or MRI were searched in MEDLINE and EMBASE, up to August 25, 2021. The reference standard for tumor viability was surgical pathology. The meta-analytic pooled sensitivity and specificity of the viable category using each criterion were calculated using a bivariate random-effects model and compared using bivariate meta-regression.

Results

For five eligible studies (430 patients with 631 treated observations), the pooled per-lesion sensitivities and specificities were 58% (95% confidence interval [CI], 45%–70%) and 93% (95% CI, 88%–96%) for the LR-TR viable category and 56% (95% CI, 42%–69%) and 86% (95% CI, 72%–94%) for the mRECIST viable category, respectively. The LR-TR viable category provided significantly higher pooled specificity (p < 0.01) than the mRECIST but comparable pooled sensitivity (p = 0.53).

Conclusion

The LR-TR algorithm demonstrated better specificity than mRECIST, without a significant difference in sensitivity for the diagnosis of pathologically viable HCC after LRT.

How to Use LI-RADS to Report Liver CT and MRI Observations

Primary liver cancer is the fourth leading cause of cancer-related deaths worldwide, with hepatocellular carcinoma (HCC) comprising the vast majority of primary liver malignancies. Imaging plays a central role in HCC diagnosis and management. As a result, the content and structure of radiology reports are of utmost importance in guiding clinical management. The Liver Imaging Reporting and Data System (LI-RADS) provides guidance for standardized reporting of liver observations in patients who are at risk for HCC. LI-RADS standardized reporting intends to inform patient treatment and facilitate multidisciplinary communication and decisions, taking into consideration individual clinical factors. Depending on the context, observations may be reported individually, in aggregate, or as a combination of both. LI-RADS provides two templates for reporting liver observations: in a single continuous paragraph or in a structured format with keywords and imaging findings. The authors clarify terminology that is pertinent to reporting, highlight the benefits of structured reports, discuss the applicability of LI-RADS for liver CT and MRI, review the elements of a standardized LI-RADS report, provide guidance on the description of LI-RADS observations exemplified with two case-based reporting templates, illustrate relevant imaging findings and components to be included when reporting specific clinical scenarios, and discuss future directions. An invited commentary by Yano is available online. Online supplemental material is available for this article. Work of the U.S. Government published under an exclusive license with the RSNA.

Up-to-Date Role of CT/MRI LI-RADS in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of mortality worldwide and a major healthcare burden in most societies. Computed tomography (CT) and magnetic resonance imaging (MRI) play a pivotal role in the medical care of patients with or at risk for hepatocellular carcinoma (HCC). When stringent imaging criteria are fulfilled, CT and MRI allow for diagnosis, staging, and assessment of response to treatment, without the need for invasive workup, and can inform clinical decision making. Owing to the central role of these imaging modalities in HCC management, standardization is essential to facilitate proper imaging technique, accurate interpretation, and clear communication among all stakeholders in both the clinical practice and research settings. The Liver Imaging Reporting and Data System (LI-RADS) is a comprehensive system that provides standardization across the continuum of HCC imaging, including ordinal probabilistic approach for reporting that directs individualized management. This review discusses the up-to-date role of CT and MRI in HCC imaging from the LI-RADS perspective. It also provides a glimpse into the future by discussing how advances in knowledge and technology are likely to enrich the LI-RADS approach.