Using Indocyanine Green Extraction to Predict Liver Function After Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma

Evolution of Response-Based Radiotherapy for Hepatocellular Cancer

ABSTRACT

Stereotactic body radiation therapy has emerged as a safe and effective treatment modality for properly selected hepatocellular cancer (HCC) patients with normal liver function. However, many HCC patients have reduced baseline liver function due to underlying cirrhosis or prior liver-directed therapies. Therefore, because of the increased risk of hepatotoxicity, the use of stereotactic body radiation therapy for patients with reduced liver function has been approached with caution. Individualized, response-based radiotherapy incorporates models, imaging tools, and biomarkers that determine the dose-response relationship of the liver before, during, and after treatment and has been useful in reducing the likelihood of liver damage without sacrificing tumor control. This review discusses the evolution of response-based radiotherapy for HCC and highlights areas for further investigation.

A human-in-the-loop based Bayesian network approach to improve imbalanced radiation outcomes prediction for hepatocellular cancer patients with stereotactic body radiotherapy

Background

Imbalanced outcome is one of common characteristics of oncology datasets. Current machine learning approaches have limitation in learning from such datasets. Here, we propose to resolve this problem by utilizing a human-in-the-loop (HITL) approach, which we hypothesize will also lead to more accurate and explainable outcome prediction models.

Methods

A total of 119 HCC patients with 163 tumors were used in the study. 81 patients with 104 tumors from the University of Michigan Hospital treated with SBRT were considered as a discovery dataset for radiation outcomes model building. The external testing dataset included 59 tumors from 38 patients with SBRT from Princess Margaret Hospital. In the discovery dataset, 100 tumors from 77 patients had local control (LC) (96% of 104 tumors) and 23 patients had at least one grade increment of ALBI (I-ALBI) during six-month follow up (28% of 81 patients). Each patient had a total of 110 features, where 15 or 20 features were identified by physicians as expert knowledge features (EKFs) for LC or I-ALBI prediction. We proposed a HITL based Bayesian network (HITL-BN) approach to enhance the capability of selecting important features from imbalanced data in terms of accuracy and explainability through humans' participation by integrating feature importance ranking and Markov blanket algorithms. A pure data-driven Bayesian network (PD-BN) method was applied to the same discovery dataset of HCC patients as a benchmark.

Results

In the training and testing phases, the areas under receiver operating characteristic curves of the HITL-BN models for LC or I-ALBI prediction during SBRT are 0.85 (95% confidence interval: 0.75-0.95) or 0.89 (0.81-0.95) and 0.77 or 0.78, respectively. They significantly outperformed the during-treatment PD-BN model in predicting LC or I-ALBI based on the discovery cross-validation and testing datasets from the Delong tests.

Conclusion

By allowing the human expert to be part of the model building process, the HITL-BN approach yielded significantly improved accuracy as well as better explainability when dealing with imbalanced outcomes in the prediction of post-SBRT treatment response of HCC patients when compared to the PD-BN method.

Role of Functional MRI in Liver SBRT: Current Use and Future Directions

Stereotactic body radiation therapy (SBRT) is an emerging treatment for liver cancers whereby large doses of radiation can be delivered precisely to target lesions in 3-5 fractions. The target dose is limited by the dose that can be safely delivered to the non-tumour liver, which depends on the baseline liver functional reserve. Current liver SBRT guidelines assume uniform liver function in the non-tumour liver. However, the assumption of uniform liver function is false in liver disease due to the presence of cirrhosis, damage due to previous chemo- or ablative therapies or irradiation, and fatty liver disease. Anatomical information from magnetic resonance imaging (MRI) is increasingly being used for SBRT planning. While its current use is limited to the identification of target location and size, functional MRI techniques also offer the ability to quantify and spatially map liver tissue microstructure and function. This review summarises and discusses the advantages offered by functional MRI methods for SBRT treatment planning and the potential for adaptive SBRT workflows.

LRFNet: A deep learning model for the assessment of liver reserve function based on Child-Pugh score and CT image

BACKGROUND AND OBJECTIVE

Liver reserve function should be accurately evaluated in patients with hepatic cellular cancer before surgery to evaluate the degree of liver tolerance to surgical methods. Meanwhile, liver reserve function is also an important indicator for disease analysis and prognosis of patients. Child-Pugh score is the most widely used liver reserve function evaluation and scoring system. However, this method also has many shortcomings such as poor accuracy and subjective factors. To achieve comprehensive evaluation of liver reserve function, we developed a deep learning model to fuse bimodal features of Child-Pugh score and computed tomography (CT) image.

METHODS

1022 enhanced abdomen CT images of 121 patients with hepatocellular carcinoma and impaired liver reserve function were retrospectively collected. Firstly, CT images were pre-processed by de-noising, data amplification and normalization. Then, new branches were added between the dense blocks of the DenseNet structure, and the center clipping operation was introduced to obtain a lightweight deep learning model liver reserve function network (LRFNet) with rich liver scale features. LRFNet extracted depth features related to liver reserve function from CT images. Finally, the extracted features are input into a deep learning classifier composed of fully connected layers to classify CT images into Child-Pugh A, B and C. Precision, Specificity, Sensitivity, and Area Under Curve are used to evaluate the performance of the model.

RESULTS

The AUC by our LRFNet model based on CT image for Child-Pugh A, B and C classification of liver reserve function was 0.834, 0.649 and 0.876, respectively, and with an average AUC of 0.774, which was better than the traditional clinical subjective Child-Pugh classification method.

CONCLUSION

Deep learning model based on CT images can accurately classify Child-Pugh grade of liver reserve function in hepatocellular carcinoma patients, provide a comprehensive method for clinicians to assess liver reserve function before surgery.

Clinical and technical challenges of cancer reirradiation: Words of wisdom

Since the development of new radiotherapy techniques that have improved healthy tissue sparing, reirradiation (reRT) has become possible. The selection of patients eligible for reRT is complex given that it can induce severe or even fatal side effects. The first step should therefore be to assess, in the context of multidisciplinary staff meeting, the patient's physical status, the presence of sequelae resulting from the first irradiation and the best treatment option available. ReRT can be performed either curatively or palliatively to treat a cancer-related symptom that is detrimental to the patient's quality of life. The selected techniques for reRT should provide the best protection of healthy tissue. The construction of target volumes and the evaluation of constraints regarding the doses that can be used in this context have not yet been fully codified. These points raised in the literature suggest that randomized studies should be undertaken to answer pending questions.

Gadoxetic Acid Uptake Rate as a Measure of Global and Regional Liver Function as Compared to Indocyanine Green Retention, Albumin-Bilirubin Score, and Portal Venous Perfusion

Purpose

Global and regional liver function assessments are important for defining the magnitude and spatial distribution of dose to preserve functional liver parenchyma and reduce incidence of hepatotoxicity from radiation therapy for intrahepatic cancer treatment. This individualized liver function-guided radiation therapy strategy is critical for patients with heterogeneous and poor liver function, often observed in cirrhotic patients treated for hepatocellular carcinoma. This study aimed to validate k₁ as a measure of global and regional function through comparison with 2 well-regarded global function measures: indocyanine green retention (ICGR) and albumin-bilirubin (ALBI).

Methods and Materials

Seventy-nine dynamic gadoxetic acid enhanced magnetic resonance imaging scans were acquired in 40 patients with hepatocellular carcinoma in institutional review board approved prospective protocols. Portal venous perfusion (k_pv) was quantified from gadoxetic acid enhanced magnetic resonance imaging using a dual-input 2-compartment model, and gadoxetic acid uptake rate (k₁) was fitted using a linearized single-input 2-compartment model chosen for robust k₁ estimation. Four image-derived measures of global liver function were tested: (1) mean k₁ multiplied by liver volume (k₁V_L) (functional volume), (2) mean k₁ multiplied by blood distribution volume (k₁V_dis)_, (3) mean k_pv, and (4) liver volume (V_L). The measure's correlation with corresponding ICGR and ALBI tests was assessed using linear regression. Voxel-wise similarity between k₁ and k_pv was compared using Spearman ranked correlation.

Results

Significant correlations (P < .05) with ICGR and ALBI were found for k₁V_L, k₁V_dis, and V_L (in order of strength), but not for mean k_pv. The mean ranked correlation coefficient between k₁ and k_pv maps was 0.09. k₁ and k_pv maps were predominantly mismatched in patients with poor liver function.

Conclusions

The metric combining function and liver volume (k₁V_L) was a stronger measure of global liver function compared with perfusion or liver volume alone, especially in patients with poor liver function. Gadoxetic acid uptake rate is promising for both global and regional liver function.

LI-RADS Treatment Response Algorithm: Performance and Diagnostic Accuracy With Radiologic-Pathologic Explant Correlation in Patients With SBRT-Treated Hepatocellular Carcinoma

PURPOSE

Our purpose was to evaluate the accuracy of LI-RADS Treatment Response Algorithm (LR-TRA) for assessing the viability of hepatocellular carcinoma (HCC) treated with stereotactic body radiation therapy (SBRT), using explant pathology as the gold standard.

METHODS AND MATERIALS

This retrospective study included patients who underwent SBRT for locoregional treatment of HCC between 2008 and 2019 with subsequent liver transplantation. Five radiologists independently assessed all treated lesions by using the LR-TRA. Imaging and posttransplant histopathology were compared. Lesions were categorized as either completely (100%) or incompletely (<100%) necrotic, and performance characteristics and predictive values for the LR-TR viable and nonviable categories were calculated for each reader. Interreader reliability was calculated using the Fleiss kappa test.

RESULTS

A total of 40 treated lesions in 26 patients (median age, 63 years [interquartile range, 59.4-65.5]; 23 men) were included. For lesions treated with SBRT, sensitivity for incomplete tumor necrosis across readers ranged between 71% and 86%, specificity between 85% and 96%, and positive predictive value between 86% and 92%, when the LR-TR equivocal category was treated as nonviable, accounting for subject clustering. When the LR-TR equivocal category was treated as viable, sensitivity of complete tumor necrosis for lesions treated with SBRT ranged from 88% to 96%, specificity from 71% to 93%, and negative predictive value from 85% to 96%. Interreader reliability was fair (k = 0.22; 95% confidence interval, 0.13-0.33). Although a loss of arterial phase hyperenhancement (APHE) was highly correlated with pathologically nonviable tumor on explant, almost half of the patients with APHE had pathologically nonviable tumor on explant.

CONCLUSIONS

LR-TRA v2018 performs well for predicting complete and incomplete necrosis in HCC treated with SBRT. In contrast to other locoregional therapies, the presence of APHE after SBRT does not always indicate viable tumor and suggests that observation may be an appropriate strategy for these patients.

Leveraging Blood-Based Diagnostics to Predict Tumor Biology and Extend the Application and Personalization of Radiotherapy in Liver Cancers

While the incidence of primary liver cancers has been increasing worldwide over the last few decades, the mortality has remained consistently high. Most patients present with underlying liver disease and have limited treatment options. In recent years, radiotherapy has emerged as a promising approach for some patients; however, the risk of radiation induced liver disease (RILD) remains a limiting factor for some patients. Thus, the discovery and validation of biomarkers to measure treatment response and toxicity is critical to make progress in personalizing radiotherapy for liver cancers. While tissue biomarkers are optimal, hepatocellular carcinoma (HCC) is typically diagnosed radiographically, making tumor tissue not readily available. Alternatively, blood-based diagnostics may be a more practical option as blood draws are minimally invasive, widely availability and may be performed serially during treatment. Possible blood-based diagnostics include indocyanine green test, plasma or serum levels of HGF or cytokines, circulating blood cells and genomic biomarkers. The albumin–bilirubin (ALBI) score incorporates albumin and bilirubin to subdivide patients with well-compensated underlying liver dysfunction (Child–Pugh score A) into two distinct groups. This review provides an overview of the current knowledge on circulating biomarkers and blood-based scores in patients with malignant liver disease undergoing radiotherapy and outlines potential future directions.

Evaluation of Pretreatment Magnetic Resonance Elastography for the Prediction of Radiation-Induced Liver Disease

Purpose

Magnetic resonance (MR) elastography (E) is a noninvasive technique for quantifying liver stiffness (LS) for fibrosis. This study evaluates whether LS is associated with risk of developing radiation-induced liver disease (RILD) in patients receiving liver-directed radiation therapy (RT).

Methods and Materials

Based on prior studies, LS ≤3 kPa was considered normal and LS >3.0 kPa as representing fibrosis. RILD was defined as an increase in Child-Pugh (CP) score of ≥2 from baseline within 1 year of RT. Univariate and multivariate Cox models were used to assess correlation.

Results

One hundred two patients, 51 with primary liver tumors and 51 with liver metastases, were identified with sufficient follow-up. In univariate models, pre-RT LS >3.0 kPa (hazard ratio [HR] 4.9; 95% confidence interval [CI], 1.6-14; P = .004), body mass index (BMI), clinical cirrhosis, CP score, albumin-bilirubin (ALBI) grade 2, primary liver tumor, and mean liver dose were significantly associated with risk of post-RT RILD. In a multivariate analysis, LS >3.0 and mean liver dose both were significantly associated with RILD risk.

Conclusions

Elevated pre-RT LS is associated with an increased risk of RILD in patients receiving liver-directed RT.

The Potential for Midtreatment Albumin-Bilirubin (ALBI) Score to Individualize Liver Stereotactic Body Radiation Therapy

PURPOSE

Our individualized functional response adaptive approach to liver stereotactic body radiation therapy (SBRT) with assessment of indocyanine green (ICG) retention at baseline and midtreatment to detect subclinical changes in liver function, permitting dose adjustment, has decreased toxicity while preserving efficacy. We hypothesized that assessment of the albumin-bilirubin (ALBI) score at baseline and midtreatment would allow for more practical identification of patients at risk for treatment-related toxicity (TRT).

METHODS AND MATERIALS

Patients with hepatocellular carcinoma were treated on 3 prospective institutional review board-approved trials using baseline and midtreatment ICG to deliver individualized functional response adaptive liver SBRT. Patients received 3 or 5 fractions, with fraction 3 followed by a 1-month treatment break. TRT was a ≥2-point rise in Child-Pugh score within 6 months of SBRT. Logistic regression was used to estimate odds ratios (ORs) and confidence intervals (CIs) for assessment of TRT. Area under the receiver operating curve was used to compare predictive ability across models.

RESULTS

In total, 151 patients underwent 166 treatments. Baseline Child-Pugh class and ALBI grade were A (66.9%), B (31.3%), or C (1.8%) and 1 (25.9%), 2 (65.7%), or 3 (8.4%), respectively. Thirty-five patients (20.3%) experienced TRT. On univariate analysis, baseline ALBI (OR, 1.8; 95% CI, 1.24-2.62; P = .02), baseline ICG (OR, 1.66; 95% CI, 1.17-2.35; P = .04), and change in ALBI (OR, 3.07; 95% CI, 1.29-7.32; P = .003) were associated with increased odds of TRT. ALBI-centric models performed similarly to ICG-centric models on multivariate analyses predicting toxicity (area under the receiver operating curve of 0.79 for both). In a model incorporating baseline and midtreatment change in ALBI and ICG, both ALBI values were statistically significantly associated with toxicity, whereas ICG values were not.

CONCLUSIONS

Incorporation of midtreatment change in ALBI in addition to baseline ALBI improves the ability to predict TRT in patients with hepatocellular carcinoma receiving SBRT. Our findings suggest that functional response adaptive treatment could be implemented in a practical manner because the ALBI score is easily obtained from standard laboratory values.

TNFR1 and the TNFα axis as a targetable mediator of liver injury from stereotactic body radiation therapy

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Elevated soluble TNFR1 levels are predictive of liver toxicity among patients receiving radiation.

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Soluble TNFR1 levels do not independently predict liver toxicity when included in models with ALBI and mean liver dose.

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Data suggest that liver inflammation mediates toxicity after liver irradiation and that the TNFα axis is associated with this inflammation.

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Future studies of should evaluate approaches that target pre-treatment inflammation to reduce the risk of toxicity.

Introduction

Radiation therapy for the management of intrahepatic malignancies can adversely affect liver function. Liver damage has been associated with increased levels of inflammatory cytokines, including tumor necrosis factor alpha (TNFα). We hypothesized that an inflammatory state, characterized by increased soluble TNFα receptor (sTNFR1), mediates sensitivity of the liver to radiation.

Materials/Methods

Plasma samples collected during 3 trials of liver radiation for liver malignancies were assayed for sTNFR1 level via enzyme-linked immunosorbent assay (ELISA). Univariate and multivariate logistic regression and longitudinal models were used to characterize associations between liver toxicity (defined as a ≥2-point increase in Child-Pugh [CP] score within 6 months of radiation treatment) and sTNFR1 levels, ALBI score, biocorrected mean liver dose (MLD), age, and baseline laboratory values.

Results

Samples from 78 patients given liver stereotactic body radiation therapy [SBRT] (92%) or hypofractionated radiation were examined. There was a significant association between liver toxicity and sTNFR1 levels, and higher values were associated with increased toxicity over a range of mean liver doses. When ALBI score and biocorrected dose were included in the model with sTNFR1, baseline ALBI score and change in ALBI (ΔALBI) were significantly associated with toxicity, but sTNFR1 was not. Baseline aminotransferase levels also predicted toxicity but not independently of ALBI score.

Conclusions

Elevated plasma sTNFR1 levels are associated with liver injury after liver radiation, suggesting that elevated inflammatory cytokine activity is a predictor of radiation-induced liver dysfunction. Future studies should determine whether administration of agents that decrease inflammation prior to treatment is warranted.

Serum Levels of Hepatocyte Growth Factor and CD40 Ligand Predict Radiation-Induced Liver Injury

BACKGROUND: Declining liver function is a concerning side effect associated with radiation therapy. Biomarkers of liver toxicity would be useful in personalizing therapy. METHODS: As part of two prospective clinical trials examining adaptive radiation therapy, we collected serum samples from patients receiving liver radiation. We performed a screen of 22 cytokines using a multiplex assay then used ELISA to quantify the cytokines of greatest interest. Subjects were split into screening and validation cohorts. Toxicity was defined as an increase in Child-Pugh score of 2 points or greater within 6 months. Logistic regression models were used to estimate the relationship between our toxicity endpoint and serum cytokine concentrations. RESULTS: Our initial screen (46 subjects, 11 events) identified hepatocyte growth factor (HGF), CD40L (CD154), and eotaxin (CCL11) as potentially predictive of toxicity. We then tested these markers in an expanded patient cohort (104 subjects, 18 events) with a batch correction due to varying age of the samples which confirmed that high HGF and low CD40L were associated with a subsequent decline in liver function following radiation therapy. Multivariate analysis factoring in baseline Child-Pugh score and mean liver radiation dose demonstrated that HGF and CD40L were potentially predictive of toxicity (HGF OR 4.3, P = .009; CD40L OR 0.5 P = .06). Additionally, higher than median baseline HGF levels (1.4 ng/ml) were significantly associated with decreased survival following liver radiation (27.1 vs 14.5 months, P = .03). CONCLUSIONS: Our study identifies high HGF and low CD40L as potential markers of liver toxicity following radiation therapy.

Clinical Case Panel: Treatment Alternatives for Inoperable Hepatocellular Carcinoma

Surgical resection or liver transplantation offers the best chance of cure for patients with hepatocellular carcinoma (HCC). Unfortunately, most patients are not good candidates for liver resection due to locally advanced disease or compromised liver function. Moreover, liver transplantation waiting lists are long. For those cases not amenable for resection, a variety of local treatment modalities are available, such as image-guided ablative procedures, transarterial chemoembolization, and radioembolization, as well as external beam radiation. HCC presentation can vary considerably in size, number, and location of lesions. The management of inoperable HCC is, therefore, quite complex, and there is a lack of consensus on the best local treatment modality for each type tumor presentation. Here, we present 4 clinical case scenarios representative of commonly seen cases in the clinical setting, with different therapeutic perspectives from institutions with high expertise in the management of HCC.

Radiation-Induced Liver Disease and Modern Radiotherapy

Modern radiotherapy techniques have enabled high focal doses of radiation to be delivered to patients with primary and secondary malignancies of the liver. The current clinical practice of radiation oncology has benefitted from decades of research that have informed how to achieve excellent local control and survival outcomes with minimal toxicities. Still, one of the most devastating consequences of radiation to the liver remains a challenge: radiation-induced liver disease (RILD). Here, we will review the current understanding of classic and nonclassic RILD from a clinical perspective, the evaluation and management of patients who are at risk of developing RILD, methods to reduce the likelihood of RILD using modern radiation techniques, and the diagnosis and treatment of radiation-related liver toxicities.

Radiotherapy for Hepatocellular Carcinoma

For patients with unresectable or medically inoperable hepatocellular carcinoma, there are many local and regional therapies available, including stereotactic body radiotherapy, radiofrequency ablation, and transcatheter embolic approaches. This article will describe these treatment options and review the current comparative literature, suggesting that stereotactic body radiotherapy provides similar or better tumor control and a favorable side effect profile.