Yttrium-90 Radiation Segmentectomy of Hepatocellular Carcinoma: A Comparative Study of the Effectiveness, Safety, and Dosimetry of Glass-Based versus Resin-Based Microspheres

Radiation segmentectomy for early hepatocellular carcinoma is curative

In this expert opinion, we provide the rationale for concluding that radiation segmentectomy (using the RADSEG method) - a technique involving the transarterial delivery of an ablative, complete necrosis-inducing dose of yttrium-90 radiotherapy - is curative in limited-disease burden hepatocellular carcinoma (HCC). Currently, curative options for early stage and other carefully selected HCC cases include transplantation, resection, and ablation. Because of issues with organ availability, co-morbidities preventing resection, and tumour size and location limiting ablation, other treatments are necessary for this selected patient population. The RADSEG method has evolved into an intra-arterial approach in this setting, with long-term outcomes comparable to ablation, resection, and transplantation. It is proposed that yttrium-90 radioembolisation, applying the RADSEG technique, be formally recognised as curative for early HCC.

Dose-response relationships in Y90 resin microsphere radioembolization for patients with hepatocellular carcinoma: insights from a Brazilian cohort

OBJECTIVE

To evaluate the relationship between the absorbed dose and radiological response in patients with hepatocellular carcinoma undergoing resin microsphere radioembolization to enhance treatment precision and potentially adjust protocols for better outcomes.

METHODS

This single-center retrospective study was conducted at a quaternary care center in Brazil and comprised 27 patients with 58 target lesions treated between November 2014 and April 2023. The patients' dosimetric profiles were analyzed using advanced imaging software to assess post-treatment clinical and radiological responses. This study explored the correlation between the absorbed doses and tumor objective responses using statistical analyses to confirm the findings.

RESULTS

Higher absorbed doses were significantly associated with improved objective responses in the target lesions. The analysis demonstrated that achieving higher dosimetric thresholds correlated with better clinical outcomes, suggesting that a dose-response relationship is essential to optimize treatment protocols.

CONCLUSION

These findings emphasize the importance of personalized dosimetry in managing hepatocellular carcinoma using resin microsphere radioembolization. By quantifying the absorbed dose and understanding its impact on tumor response, treatment strategies can be tailored to enhance efficacy and potentially shift palliative treatments toward curative outcomes. This study provides a crucial foundation for dosimetric adjustment and highlights the need for further research in this area, particularly in Brazil.

LI-RADS radiation-based treatment response algorithm for HCC: what to know and how to use it

Locoregional treatments (LRT) continue to advance for hepatocellular carcinoma (HCC). Selective internal radiation therapy (SIRT) or transarterial radioembolization (TARE) with radioactive 90 Yttrium (Y90) microspheres is currently widely accepted, and external beam and stereotactic body radiation (EBRT/SBRT) are increasingly used as LRT1-5. Assessment of treatment response after these radiation-based therapies can be challenging, given that the adjacent liver also undergoes treatment related changes, inflammatory changes occur, and there is a variable time for response to develop. In 2017, the liver imaging reporting and data system (LI-RADS) workgroup initially developed a single algorithm for the imaging assessment of treatment response encompassing all types of locoregional therapies, the LI-RADS treatment response (LR-TR) algorithm. Recognizing that response and imaging patterns differ between radiation and non-radiation based therapies, the LR-TR working group recently updated the algorithm to reflect the unique characteristics of tumor response for therapies involving radiation. This article aims to elucidate the changes in the new version of the LI-RADS TR, with a guide for algorithm utilization and illustration of expected and unexpected findings post liver directed therapies for HCC.

LI-RADS CT/MRI Radiation Treatment Response Algorithm Version 2024: Category Redistribution and Short-Term Outcomes in Patients Undergoing Y-90 Radioembolization for HCC

Background: LI-RADS CT/MRI Radiation Treatment Response Algorithm (TRA) version 2024 (v2024) addresses a pitfall of the earlier algorithm relating to expected persistent enhancement of hepatocellular carcinoma (HCC) responding to radiation. v2024 removes LR-TR Equivocal, introduces LR-TR Nonprogressing (stable or decreasing masslike enhancement), and more narrowly defines LR-TR Viable (new or increasing masslike enhancement). Objective: To evaluate in patients with HCC treated by Y-90 radioembolization the redistribution of categories in LI-RADS CT/MRI Radiation TRA v2024 versus LI-RADS CT/MRI TRA version 2018 (v2018) and to assess short-term outcomes of v2024 categories. Methods: This retrospective study included 242 patients (57 women, 185 men; median age, 65 years) with 319 HCCs treated by Y-90 radioembolization from February 2011 to March 2022 and evaluated by initial 3-month posttreatment CT or MRI. Two radiologists assigned v2018 and v2024 categories; a third radiologist resolved discrepancies. The radiologists also assessed available second posttreatment CT or MRI examinations using v2024. Overall survival (OS) was determined. Results: On initial follow-up, by v2018, 18 (5.6%) lesions were LR-TR Nonviable, 21 (6.6%) LR-TR Equivocal, and 280 (87.8%) LR-TR Viable; by v2024, 18 (5.6%) were LR-TR Nonviable, 182 (57.1%) LR-TR Nonprogressing, and 119 (37.3%) LR-TR Viable. All LR-TR Equivocal and 161 (57.5%) LR-TR Viable lesions by v2018 were recategorized as LRTR Nonprogressing by v2024. Of 96 LR-TR Nonprogressing lesions with second follow-up, 63 (65.6%) remained LRTR Nonprogressing, 19 (19.8%) transitioned to LR-TR Nonviable, and 14 (14.6%) transitioned to LR-TR Viable. Of 29 LR-TR Viable lesions by v2024 with second follow-up, 23 (79.3%) remained LR-TR Viable, and 6 (20.7%) transitioned to LR-TR Nonprogressing. By Kaplan-Meier analysis using initial categories, OS showed no significant difference between LR-TR Equivocal and LR-TR Viable for v2018 (p=.05) but was significantly worse for LR-TR Viable than LRTR Nonprogressing for v2024 (p<.001). Conclusion: For v2024, LR-TR Viable was substantially less frequent versus v2018, and the majority of lesions were assigned LR-TR Nonprogressing. Using v2024, most LR-TR Viable lesions and the majority of LR-TR Nonprogressing lesion on initial follow-up remained as such on later imaging. Initial v2024 categories were associated with OS. Clinical Impact: The findings support the revisions in v2024.

Initial Experience with Single-Session Resin-Based Transarterial Radioembolization Mapping and Treatment of Small Hepatocellular Carcinomas

BACKGROUND/OBJECTIVES

Studies have indicated that forgoing lung shunt fraction measurement in select patients undergoing Yttrium 90 (Y90) transarterial radioembolization (TARE) may be safe without sacrificing efficacy. This study evaluated the safety and efficacy of a streamlined treatment in patients with small hepatocellular carcinoma (HCC) receiving resin-based TARE.

METHODS

Patients who received single-session Y90 TARE between September 2023 and May 2024 were retrospectively evaluated. Treatment response was evaluated at the 3-month follow-up using the modified Response Evaluation Criteria in Solid Tumors (mRECIST) criteria. Adverse events (AEs) ≥ Grade 3 were recorded post-procedurally at 3 months. The time from the interventional radiology clinic visit to the procedure date was compared to patients receiving the conventional TARE treatment.

RESULTS

Ten consecutive patients were treated with 12 treatments. Each treatment targeted an isolated lesion with median size of 2.5 cm (IQR: 2.1, 2.9). Two patients received two treatments (one for treatment of a separate lesion and the other for the initial incomplete targeting of the tumor). The median delivered tumor dose was 377.7 Gy (IQR: 246.5, 570.1). No patients developed ≥ Grade 3 AEs post-TARE. Complete response was achieved in 11/12 patients (92%). The conventional cohort consisted of 60 patients, all OPTN T2 treated with radiation segmentectomy with glass microspheres. Patients undergoing SSMT had a median time from clinic visit to treatment of 26.5 days (IQR: 15.3, 39) vs. 61 days (IQR: 48, 88.8) in the conventional TARE group (p < 0.001).

CONCLUSIONS

Streamlined single-session resin-based Y90-TARE in patients with OPTN T2 stage HCC is feasible, efficacious, safe, and associated with reduced time to treatment.

The Impact of Radiation Dose and Tumour Burden on Outcomes in Hepatocellular Carcinoma: 11-Year Experience in a 413-Patient Cohort Treated with Yttrium-90 Resin Microsphere Radioembolisation

Introduction

Transarterial radioembolisation (RE) using yttrium-90 (Y-90) microspheres is a widely used locoregional therapy for a broad spectrum of hepatocellular carcinoma (HCC) given its favourable safety profile. We evaluated the real-world outcomes of unresectable HCC treated with resin Y-90 RE and the relationship between tumour absorbed dose and subsequent curative therapy with survival.

Methods

Included were consecutive patients treated with Y-90 resin microspheres RE for unresectable HCC between January 2008 and May 2019 at the National Cancer Centre Singapore/Singapore General Hospital. The outcomes were stratified by tumour burden, distribution, presence of portal vein invasion (PVI) and liver function to improve prognostication.

Results

The median overall survival (OS) evaluated on 413 included patients was 20.9 months (95% CI: 18.2-24.0). More than half of the patients (214/413, 51.8%) had HCC beyond up-to-seven criteria, and 37.3% had portal vein invasion (154/413, 37.3%). Majority (71.7%) had dosimetry calculated based on the partition model. Patients who received ≥150 Gy to tumour had significantly better outcomes (OS 32.2 months, 95% CI: 18.3-46.4) than those who did not (OS 17.5 months, 95% CI: 13.7-22.7, p < 0.001). Seventy patients (17%) received curative therapies after tumour was downstaged by Y-90 RE and had better OS of 79.7 months (95% CI: 40.4 - NE) compared to those who did not receive curative therapies (OS 17.1 months; 95% CI: 13.5-20.4, p < 0.001). RE-induced liver injury was observed in 5.08% of the patients while 3.2% of the patients had possible radiation pneumonitis but none developed Grade 3-4 toxicity. For HCC without PVI, OS differed significantly with performance status, albumin-bilirubin grade, tumour distribution, and radiation dose; for HCC with PVI, Child-Pugh class and AFP were significant predictors of survival.

Conclusions

Treatment outcomes for unresectable HCC using Y-90 RE were favourable. Incorporating tumour burden and distribution improved prognostication. Patients who received tumour absorbed dose above 150 Gy had better OS. Patients who subsequently received curative therapies after being downstaged by Y-90 RE had remarkable clinical outcomes.

Long-term outcomes of Yttrium-90 transarterial radioembolization for patients with hepatocellular carcinoma

AIMS

We retrospectively assessed the long-term outcomes of Yttrium-90 (90Y) transarterial radioembolization (TARE) for hepatocellular carcinoma (HCC), focusing on overall survival (OS), radiological response, and safety.

METHODS

We included patients with HCC treated with 90Y TARE at a single center between January 2012 and December 2021 with measurable lesions and a minimum of 2 years of follow-up. Only the former was analyzed for patients with multiple TARE. The primary endpoints were long-term OS, radiological response, and safety; the secondary endpoints included predictors of OS and response, with emphasis on dosimetry. The collected data included demographics, laboratory test results, liver function, and tumor staging. Radiological response was evaluated 3-6 months post-TARE using the modified RECIST (mRECIST) criteria. OS was calculated from TARE until death or censoring. Univariate logistic regression was used to identify the predictors of complete radiological response and OS. Dosimetry was analyzed to determine correlations with mRECIST response.

RESULTS

Among 142 patients (median age 66.8, cirrhotic 92.3%; M: F = 121:21), a median OS of 16.68 months was achieved, with a complete radiological response in 31% (44/142). OS was strongly correlated with radiological response (p < 0.001). Absorbed dose ≥ 234.6 Gy was associated with complete response (p = 0.017) but not with survival (p = 0.102). Rising alpha-fetoprotein levels (p = 0.017) and worsening Child-Pugh scores post-TARE (p = 0.044) were independent predictors of mortality.

CONCLUSION

A complete radiological response is crucial for long-term survival, highlighting the need for dosimetry optimization in TARE for HCC.

Radiation Pneumonitis after Yttrium-90 Radioembolization: A Systematic Review

PURPOSE

To evaluate the available evidence of lung dosimetry and radiation pneumonitis (RP).

MATERIALS AND METHODS

The guideline regarding the maximum tolerated lung dose for yttrium-90 (90Y) radioembolization is an expert opinion (Level 5 evidence) based on a case series of 5 patients and recommends keeping the absorbed radiation dose to the lungs below 30 Gy per treatment and 50 Gy in a lifetime to prevent RP. The current understanding of the risks of RP is minimal despite its debilitating nature and high mortality rate. A systematic literature review was conducted in PubMed, Embase, Cochrane database, and Google Scholar for reported cases of RP. A database of 48 RP cases was compiled and analyzed.

RESULTS

Thirty patients were treated with resin and 16 patients with glass 90Y microspheres. The treatment device was not reported in 2 cases. RP developed a median of 3 months after radioembolization. The mortality rate was 40%. The hepatopulmonary shunt was not significantly different between the glass and the resin groups (21.2% [SD ± 14%] vs 15.6% [SD ± 7.5%]; P = .24). The radiation dose to the lungs was significantly higher in patients treated with glass compared with those with resin 90Y microspheres (41.4 Gy [SD ± 18.4] vs 21.5 Gy [SD ± 9.9]; P = .003).

CONCLUSIONS

The dose toxicity threshold for resin microspheres is lower than that of glass microspheres. The established 30-Gy dose limit may not be uniformly applicable in all cases and for both devices. The maximum tolerable lung doses should be reevaluated, and the shortcomings of the hepatopulmonary shunt calculation need to be corrected.

Resin-Based Yttrium-90 Radioembolization as a Bridging or Downstaging Treatment to Liver Transplantation for Hepatocellular Carcinoma

PURPOSE

To evaluate the outcomes of resin-based yttrium-90 (90Y) transarterial radioembolization (TARE) for hepatocellular carcinoma (HCC) as a bridging or downstaging therapy to liver transplantation (LT) in terms of safety, tumor response, recurrence, and survival.

MATERIALS AND METHODS

A single-center retrospective analysis of patients with HCC treated with resin-based TARE as bridging or downstaging treatment to LT between January 2006 and April 2021 was performed. TARE-related liver toxicity was assessed. Imaging data were analyzed to assess tumor response. Histopathological analysis of explant livers was performed to assess HCC necrosis. Survival and bridging/downstaging success predictor analysis was performed.

RESULTS

Thirty-six patients underwent resin-based TARE with the intention to bridge (33%) or downstage (67%) to LT. Overall, 44% had ≥3 HCC lesions, and 53% had bilobar disease. Median largest tumor diameter was 3.4 cm. TARE was segmental, lobar, and bilobar in 20%, 36%, and 44% of cases, respectively. In total, 17% had Grade 3 bilirubin toxicities. The objective response rate per modified Response Evaluation Criteria in Solid Tumours was 72%. Patients meeting the United Network for Organ Sharing Downstaging criteria had higher chances of successful bridging/downstaging. Twenty-three patients were transplanted. Complete pathological response was noted in 30% of explant livers. Posttransplant tumor recurrence occurred in 26% within a median follow-up period of 1,710 days. Estimated 5-year progression-free, disease-specific, and overall survival rates after LT were 89%, 69%, and 89%, respectively. For the entire patient cohort, these survival rates were 87%, 53%, and 70%, respectively.

CONCLUSIONS

Resin-based 90Y TARE can be considered a valuable treatment option for bridging or downstaging patients with HCC to LT, including patients requiring lobar or bilobar TARE for extensive tumoral disease.

Voxel-based dosimetry with integrated Y-90 PET/MRI and prediction of response of primary and metastatic liver tumors to radioembolization with Y-90 glass microspheres

PURPOSE

In this study, we aimed to evaluate the response of the primary and metastatic liver tumors to radioembolization with 90Y glass microspheres and investigate its correlations with dosimetric variables calculated with 90Y PET/MRI.

METHODS

In this ambispective study, 44 patients treated with 90Y glass microspheres and imaged with 90Y PET/MRI were included for analysis. Dosimetric analysis was performed for every perfused lesion using dose-volume histograms. Response was assessed by comparing pre-treatment and follow-up total lesion glycolysis (TLG) values derived from 18F-FDG PET imaging. The relationship between ΔTLG and log-transformed dosimetric variables was analyzed with linear mixed effects regression models. ROC analyses were performed to compare discriminatory power of the variables in predicting response and complete response.

RESULTS

Regression and ROC analyses demonstrated that mean tumor dose and almost all D values were statistically significant predictors of treatment response and complete treatment response. Specifically, D60, D70 and D80 values exhibited significantly higher discriminatory power for predicting treatment response compared to the mean dose (Dmean) delivered to tumor. High specificity cut-off values to predict response were determined as 160.75 Gy for Dmean, 95.50 Gy for D60, 89 Gy for D70, and 59.50 Gy for D80. Similarly, high-specificity cut-off values to predict complete response were 262.75 Gy for Dmean, 173 Gy for D70, 140.5 Gy for D80, and 100 Gy for D90.

CONCLUSION

In this study, we demonstrated that voxel-based dosimetry with post-treatment 90Y PET/MRI can predict response to treatment. D60, D70 and D80 variables also did have greater discriminatory power compared to Dmean in prediction of response. In addition, we present high-specificity cut-offs to predict response (CR + PR) and complete response (CR) for both Dmean and several D variables derived from dose-volume histograms.

Using Voxel-Based Dosimetry to Evaluate Sphere Concentration and Tumor Dose in Hepatocellular Carcinoma Treated with Yttrium-90 Radiation Segmentectomy with Glass Microspheres

PURPOSE

To utilize voxel-based dosimetry following radiation segmentectomy (RS) to understand microsphere distribution and validate current literature regarding radiologic and pathologic outcomes.

MATERIALS AND METHODS

A retrospective, single-center analysis of patients with solitary hepatocellular carcinoma (N = 56) treated with yttrium-90 (90Y) RS with glass microspheres (Therasphere; Boston Scientific, Marlborough, Massachusetts) from 2020 to 2022 was performed. Posttreatment voxel-based dosimetry was evaluated using Mirada DBx Build 1.2.0 Simplicit90Y software (Boston Scientific) and utilized to calculate sphere concentration to tumor as well as D70 (minimum dose to 70% total tumor volume), D90, and D99. Time to progression (TTP), treatment response, and adverse events were studied.

RESULTS

Fifty-six solitary tumors were analyzed with a median tumor diameter of 3.4 cm (range, 1.2-6.8 cm) and median tumor absorbed dose of 732 Gy (range, 252-1,776 Gy). Median sphere activity (SA) at the time of delivery was 1,446 Bq (range, 417-2,621 Bq). Median tumor sphere concentration was 12,868 spheres/mL (range, 2,655-37,183 spheres/mL). Sphere concentration into tumor and normal tissue was inversely correlated with perfused treatment volume (R2 = 0.21 and R2 = 0.39, respectively). Of the 51 tumors with posttreatment imaging, objective response was noted in 49 patients (96%) and complete response in 42 patients (82%). The median TTP was not reached with a 2-year progression rate of 11%. Fifteen patients underwent liver transplant. Median tumor necrosis was 99% (range, 80%-100%). Lower tumor volumes and higher D99 were associated with complete pathologic necrosis (P < .001 and P = .022, respectively).

CONCLUSIONS

Voxel-based dosimetry following 90Y radioembolization can be utilized to account for sphere deposition and distribution into tumor. Ablative RS with high SA yields durable radiologic and pathologic outcomes.

MIDOS: a novel stochastic model towards a treatment planning system for microsphere dosimetry in liver tumors

PURPOSE

Transarterial radioembolization (TARE) procedures treat liver tumors by injecting radioactive microspheres into the hepatic artery. Currently, there is a critical need to optimize TARE towards a personalized dosimetry approach. To this aim, we present a novel microsphere dosimetry (MIDOS) stochastic model to estimate the activity delivered to the tumor(s), normal liver, and lung.

METHODS

MIDOS incorporates adult male/female liver computational phantoms with the hepatic arterial, hepatic portal venous, and hepatic venous vascular trees. Tumors can be placed in both models at user discretion. The perfusion of microspheres follows cluster patterns, and a Markov chain approach was applied to microsphere navigation, with the terminal location of microspheres determined to be in either normal hepatic parenchyma, hepatic tumor, or lung. A tumor uptake model was implemented to determine if microspheres get lodged in the tumor, and a probability was included in determining the shunt of microspheres to the lung. A sensitivity analysis of the model parameters was performed, and radiation segmentectomy/lobectomy procedures were simulated over a wide range of activity perfused. Then, the impact of using different microspheres, i.e., SIR-Sphere®, TheraSphere®, and QuiremSphere®, on the tumor-to-normal ratio (TNR), lung shunt fraction (LSF), and mean absorbed dose was analyzed.

RESULTS

Highly vascularized tumors translated into increased TNR. Treatment results (TNR and LSF) were significantly more variable for microspheres with high particle load. In our scenarios with 1.5 GBq perfusion, TNR was maximum for TheraSphere® at calibration time in segmentectomy/lobar technique, for SIR-Sphere® at 1-3 days post-calibration, and regarding QuiremSphere® at 3 days post-calibration.

CONCLUSION

This novel approach is a decisive step towards developing a personalized dosimetry framework for TARE. MIDOS assists in making clinical decisions in TARE treatment planning by assessing various delivery parameters and simulating different tumor uptakes. MIDOS offers evaluation of treatment outcomes, such as TNR and LSF, and quantitative scenario-specific decisions.

Efficacy and Safety of Radiation Segmentectomy with 90Y Resin Microspheres for Hepatocellular Carcinoma

Background Limited data are available on radiation segmentectomy (RS) for treatment of hepatocellular carcinoma (HCC) using yttrium 90 (90Y) resin microsphere doses determined by using a single-compartment medical internal radiation dosimetry (MIRD) model. Purpose To evaluate the efficacy and safety of RS treatment of HCC with 90Y resin microspheres using a single-compartment MIRD model and correlate posttreatment dose with outcomes. Materials and Methods This retrospective single-center study included adult patients with HCC who underwent RS with 90Y resin microspheres between July 2014 and December 2022. Posttreatment PET/CT and dosimetry were performed. Adverse events were assessed using the Common Terminology Criteria for Adverse Events, version 5.0. Per-lesion and overall response rates (ie, complete response [CR], objective response, disease control, and duration of response) were assessed at imaging using the Modified Response Evaluation Criteria in Solid Tumors, and overall survival (OS) was assessed using Kaplan-Meier analysis. Results Among 67 patients (median age, 69 years [IQR, 63-78 years]; 54 male patients) with HCC, median tumor absorbed dose was 232 Gy (IQR, 163-405 Gy). At 3 months, per-lesion and overall (per-patient) CR was achieved in 47 (70%) and 41 (61%) of 67 patients, respectively. At 6 months (n = 46), per-lesion rates of objective response and disease control were both 94%, and per-patient rates were both 78%. A total of 88% (95% CI: 79 99) and 72% (95% CI: 58, 90) of patients had a per-lesion and overall duration of response of 1 year or greater. At 1 month, a grade 3 clinical adverse event (abdominal pain) occurred in one of 67 (1.5%) patients. Median posttreatment OS was 26 months (95% CI: 20, not reached). Disease progression at 2 years was lower in the group that received 300 Gy or more than in the group that received less than 300 Gy (17% vs 61%; P = .047), with no local progression in the former group through the end of follow-up. Conclusion Among patients with HCC who underwent RS with 90Y resin microspheres, 88% and 72% achieved a per-lesion and overall duration of response of 1 year or greater, respectively, with one grade 3 adverse event. In patients whose tumors received 300 Gy or more according to posttreatment dosimetry, a disease progression benefit was noted. © RSNA, 2024 Supplemental material is available for this article.

Tumor Size and Watershed Area Correlate with Incomplete Treatment and Tumor Progression after Selective Radioembolization for Hepatocellular Carcinoma

PURPOSE

To identify factors of incomplete treatment after segmental transarterial radioembolization (TARE) for treatment-naive and solitary hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

A total of 75 consecutive patients (age, 68.5 years [SD ± 8.0]; 25/75 [33.3%] women) with treatment-naive, solitary HCC underwent segmental or subsegmental TARE with glass microspheres (tumor size, 3.8 cm [SD ± 2.2]; administered dose, 222.6 Gy [SD ± 123.9]) at a single institution from November 2015 to June 2022. Radiologic response and progression-free survival (PFS) were assessed as per modified Response Evaluation Criteria in Solid Tumors.

RESULTS

Complete treatment was achieved in 48 of 75 (64.0%) patients (mean follow-up, 33.2 months [SD ± 27.4]). Patients with incomplete treatment (27/75, 36%) presented with larger tumor size (5.0 [SD ± 2.5] vs 3.1 [SD ± 1.6] cm; P = .0001), with more tumors located in the watershed zone (81.5% vs 41.7%; P = .001). These patients were less likely to be bridged to transplant or resection (22.2% vs 52.1%; P = .015). Watershed tumors demonstrated worse target tumor PFS (median PFS, 19 months vs not reached; P = .0104) and overall PFS (9.1 months vs not reached; P = .0077). Watershed location was associated with worse PFS among tumors >3 cm in size (8.4 months vs not reached; P = .035) but not in tumors ≤3 cm in size (52.2 months vs not reached; P = .915).

CONCLUSIONS

Tumor size and watershed location were associated with incomplete treatment after segmental TARE for HCC. Watershed tumors were associated with worse PFS, particularly tumors larger than 3 cm. These tumors may require careful treatment planning and repeated treatments to ensure a durable response.

Radiation Segmentectomy for the Treatment of Hepatocellular Carcinoma: A Practical Review of Evidence

Radiation segmentectomy is a versatile, safe, and effective ablative therapy for early-stage hepatocellular carcinoma. Advances in radiation segmentectomy patient selection, procedural technique, and dosimetry have positioned this modality as a curative-intent and guideline-supported treatment for patients with solitary HCC. This review describes key radiation segmentectomy concepts and summarizes the existing literary knowledgebase.

Predictive Dosimetry and Outcomes of Hepatocellular Carcinoma Treated by Yttrium-90 Resin Microsphere Radioembolization: A Retrospective Analysis Using Technetium-99m Macroaggregated Albumin Single Photon Emission CT/CT and Planning Software

PURPOSE

To characterize estimated mean absorbed tumor dose (ADT), objective response (OR), and estimated target dose of hepatocellular carcinoma (HCC) after resin microsphere yttrium-90 (90Y) radioembolization using partition dosimetry.

MATERIALS AND METHODS

In this retrospective, single-center study, multicompartment dosimetry of index tumors receiving 90Y radioembolization between October 2015 and June 2022 was performed using a commercial software package and pretreatment technetium-99m macroaggregated albumin single photon emission computed tomography (SPECT)/computed tomography (CT). In total, 101 patients with HCC underwent 102 treatments of 127 index tumors. Patients underwent imaging every 2-3 months after treatment to determine best response per modified Response Evaluation Criteria in Solid Tumors (mRECIST). Best response was defined as the greatest response category per mRECIST and categorized as OR or nonresponse (NR). A Cox proportional hazards model evaluated the probability of tumor OR and progression-free survival using ADT.

RESULTS

The median follow-up period was 148 days (interquartile range [IQR], 92-273 days). The median ADT of OR was 141.9 Gy (IQR, 89.4-215.8 Gy) compared with the median ADT of NR treatments of 70.8 Gy (IQR, 42.0-135.3 Gy; P < .001). Only ADT was predictive of response (hazard ratio = 2.79 [95% confidence interval {CI}: 1.44-5.40]; P = .003). At 6 months, an ADT of 157 Gy predicted 90.0% (95% CI: 41.3%-98.3%) probability of OR. At 1 year, an ADT of 157 Gy predicted 91.6% (95% CI: 78.3%-100%) probability of progression-free survival. Partition modeling and delivered activity were predictive of progression (P = .021 and P = .003, respectively).

CONCLUSIONS

For HCC treated with resin microspheres, tumors receiving higher ADT exhibited higher rates of OR. An ADT of 157 Gy predicted 90.0% OR at 6 months.

Vortex-assisted resin y90 delivery via 175 cm Truselect microcatheter: case factors for high residual despite double-flush protocol

PURPOSE

To report efficiency of resin y90 delivery using SIROS via 175 cm TruSelect microcatheter with double-flush protocol (40 ml dextrose total).

METHODS

IRB-approved retrospective review of all patients undergoing SIROS injection of y90 Sir-Spheres via TruSelect from 2019 through 2022 at one quaternary-care academic institution, including medical records.

RESULTS

Included were 48 infusions in 25 patients across 11 cancer histologies. Mean planned, delivered, and residual activities were 28 ± 17, 27 ± 17, 1.1 ± 0.56 mCi respectively (mean residual 4.9% ± 2.8%) across flex-dosing precalibrations including 1-day, 2-day, and 3-day SIROS (4/51, 16/51, and 28/51). Mean liver treatment volume was 483 ± 306 ml with target dose mean of 128 ± 26 Gy in non-segmentectomy cases; Radiation segmentectomy was performed in 15/48 (31%). Arterial stasis was documented in 9/48 (19%) of cases. Use of a 3-day precalibrated SIROS dose, use of activity <10 mCi, treatment of smaller liver volumes (<200 ml) and documentation of stasis were associated with higher residual activity ( P  = 0.025, P  = 0.0007, P  = 0.0177, and P  = 0.049, respectively) were associated with higher residuals.

CONCLUSION

Combining the new technologies of SIROS and the Truselect microcatheter with a double-flush protocol yielded <10% residual in 94% of y90 infusions. Future studies may clarify if the predictors of high residual dose seen here may warrant microcatheter-specific considerations for dosimetry or dose preparation at the Radiopharmacy level.

Surgery and radioembolization of liver tumors

Surgical resection is considered the curative treatment par excellence for patients with primary or metastatic liver tumors. However, less than 40% of them are candidates for surgery, either due to non-modifiable factors (comorbidities, age, liver dysfunction…), or to the invasion or proximity of the tumor to the main vascular requirements, the lack of a future liver remnant (FLR) adequate to maintain postoperative liver function, or criteria of tumor size and number. In these last factors, hepatic radioembolization has been shown to play a role as a presurgical tool, either by hypertrophy of the FLR or by reducing tumor size that manages to reduce tumor staging (term known as "downstaging"). To these is added a third factor, which is its ability to apply the test of time, which makes it possible to identify those patients who present progression of the disease in a short period of time (both locally and at distance), avoiding a unnecessary surgery. This paper aims to review RE as a tool to facilitate liver surgery, both through the experience of our center and the available scientific evidence.