Liver machine perfusion technology: Expanding the donor pool to improve access to liver transplantation.

The imbalance between organ supply and demand continues to limit the broader benefits of organ transplantation. Machine perfusion (MP) may increase the supply of donor livers by expanding the use of extended-criteria donors. Using the United Network for Organ Sharing/Organ Procurement and Transplantation Network and the Standard Transplant Analysis and Research dataset, we reviewed the effect of MP implementation on the behavior of transplant centers. We identified 15 high-utilizing MP centers that were matched to suitable controls based on volume and geographical proximity. We conducted a differences-in-differences analysis using linear regression to estimate the impact of MP adoption on the transplant centers' donor utilization. We found a significant increase in cold ischemia time and organs with donor warm ischemia time over 30 minutes (P < .05). After removing one outlier center, the analysis showed that these centers through MP accepted overall more donation after circulatory death donors, donation after circulatory death donors over 50 years old, donors with macrovesicular steatosis greater than 30% on liver biopsy, and donor warm ischemia time over 30 minutes (P < .05). MP has allowed centers to expand their use of extended-criteria donors beyond traditional cutoffs and to increase patient access to liver transplantation.

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.

Machine perfusion organ preservation: Highlights from the American Transplant Congress 2023.

The American Transplant Congress (ATC) 2023, held in San Diego, California, emerged as a pivotal platform showcasing the latest advancements in organ machine perfusion, a key area in solid organ and tissue transplantation. This year's congress, attended by over 4500 participants, including leading experts, emphasized innovations in machine perfusion technologies across various organ types, including liver, kidney, heart, and lung. A total of 85 abstracts on organ machine perfusion were identified. Noteworthy advancements included the use of normothermic machine perfusion in mitigating ex-situ reperfusion injury in liver transplantation, the potential of biomarkers in assessing organ quality, and the impact of machine perfusion on graft survival and ischemic cholangiopathy incidence. Kidney transplantation saw promising developments in novel preservation methods, such as subzero storage and pulsatile perfusion. Heart and lung sessions revealed significant progress in preservation techniques, including metabolic alterations to extend organ preservation time. The conference also highlighted the growing interest in machine perfusion applications in pediatric transplantation, multi-visceral organ recovery, Vascularized Composite Allotransplantation, and discussions on novel technologies for monitoring and optimizing perfusion protocols. Additionally, ATC 2023 included critical discussions on ethical concerns, legal implications, and the evolving definition of death in the era of machine preservation, illustrating the complex landscape of transplantation science. Overall, ATC 2023 showcased significant strides in machine perfusion and continued its tradition of fostering global knowledge exchange, further cementing machine perfusion's role as a transformative force in improving transplant outcomes and expanding the donor pool.

Normothermic Machine Perfusion of Donor Livers for Transplantation in the United States: A Randomized Controlled Trial.

OBJECTIVE: To compare conventional low-temperature storage of transplant donor livers [static cold storage (SCS)] with storage of the organs at physiological body temperature [normothermic machine perfusion (NMP)]. BACKGROUND: The high success rate of liver transplantation is constrained by the shortage of transplantable organs (eg, waiting list mortality >20% in many centers). NMP maintains the liver in a functioning state to improve preservation quality and enable testing of the organ before transplantation. This is of greatest potential value with organs from brain-dead donor organs (DBD) with risk factors (age and comorbidities), and those from donors declared dead by cardiovascular criteria (donation after circulatory death). METHODS: Three hundred eighty-three donor organs were randomized by 15 US liver transplant centers to undergo NMP (n = 192) or SCS (n = 191). Two hundred sixty-six donor livers proceeded to transplantation (NMP: n = 136; SCS: n = 130). The primary endpoint of the study was "early allograft dysfunction" (EAD), a marker of early posttransplant liver injury and function. RESULTS: The difference in the incidence of EAD did not achieve significance, with 20.6% (NMP) versus 23.7% (SCS). Using exploratory, "as-treated" rather than "intent-to-treat," subgroup analyses, there was a greater effect size in donation after circulatory death donor livers (22.8% NMP vs 44.6% SCS) and in organs in the highest risk quartile by donor risk (19.2% NMP vs 33.3% SCS). The incidence of acute cardiovascular decompensation at organ reperfusion, "postreperfusion syndrome," as a secondary outcome was reduced in the NMP arm (5.9% vs 14.6%). CONCLUSIONS: NMP did not lower EAD, perhaps related to the inclusion of lower-risk liver donors, as higher-risk donor livers seemed to benefit more. The technology is safe in standard organ recovery and seems to have the greatest benefit for marginal donors.

Observations on hydronephrosis after pig kidney transplantation in baboons.

We have seen hydronephrosis (obstructive nephropathy) at necropsy in 3 of 11 (21%) genetically-engineered pig kidneys that functioned in baboons for >36 days, even when the clinical and histopathological features of rejection were minimal. We briefly report one such case and illustrate the macroscopic and microscopic appearances of such a kidney and ureter. The causes of the observed changes remain uncertain. In our small experience, there seems to be no correlation between the development of hydronephrosis and (i) the surgical technique, (ii) the genotype of the pig, (iii) the length of the pig ureter, or (iv) the immunosuppressive and anti-inflammatory therapy administered. We suggest that the distal ureteric thickening may be the result of an inflammatory response. In two cases, we resolved the problem by carrying out a secondary side-to-side anastomosis between the proximal pig ureter and the baboon bladder.

Heterogeneity in transplant center responses to the minimum acceptance criteria across UNOS regions.

Transplantation of organs from increased risk donors for infection transmission (IRDs) is increasing. These organs confer survival benefit to recipients. This study examined transplant center acceptance policies for IRD kidneys across United Network for Organ Sharing (UNOS) regions, based on transplant centers' annual responses to the Minimum Acceptance Criteria (MAC) for acceptance of IRD kidneys, and the association with national and regional IRD kidney utilization. De-identified MAC responses from all transplant centers in the United States from 2007 to 2019 were obtained. Implementation of MAC responses into practice was evaluated based on annual rates of recovery and transplantation of IRD kidneys, by MAC and UNOS region. Nationally, the number of transplant centers willing to accept IRD kidneys across all criteria increased from 22% in 2007 to 64% in 2019. Acceptance rates increased markedly from donors with intravenous drug use and other potential HIV exposures. However, significant heterogeneity exists in transplant center willingness to accept IRD kidneys, both regionally and between criteria. Trends towards increasing acceptance are strongly associated with higher rates of recovery and transplantation of IRD kidneys. Further research on provider- and center-based refusal to consider IRD kidneys for waitlisted patients is needed to improve utilization of this organ pool.

Histopathology of pig kidney grafts with/without expression of the carbohydrate Neu5Gc in immunosuppressed baboons.

INTRODUCTION: Pigs deficient in three glycosyltransferase enzymes (triple-knockout [TKO] pigs, that is, not expressing the three known carbohydrate xenoantigens) and expressing 'protective' human transgenes are considered a likely source of organs for transplantation into human recipients. Some human sera have no or minimal natural antibody binding to red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs) from TKO pigs. However, all Old World monkeys exhibit natural antibody binding to TKO pig cells. The xenoantigen targets of Old World monkey natural antibodies are postulated to be carbohydrate moieties exposed when the expression of the carbohydrate N-glycolylneuraminic acid (Neu5Gc) is deleted. The aim of this study was to compare the survival in baboons and histopathology of renal grafts from pigs that either (a) expressed Neu5Gc (GTKO pigs; Group 1) or (b) did not express Neu5Gc (GTKO/CMAHKO [DKO] or TKO pigs; Group 2). METHODS: Life-supporting renal transplants were carried out using GTKO (n = 5) or DKO/TKO (n = 5) pig kidneys under an anti-CD40mAb-based immunosuppressive regimen. RESULTS: Group 1 baboons survived longer than Group 2 baboons (median 237 vs. 35 days; mean 196 vs. 57 days; p < 0.07) and exhibited histopathological features of antibody-mediated rejection in only two kidneys. Group 2 exhibited histopathological features of antibody-mediated rejection in all five grafts, with IgM and IgG binding to renal interstitial arteries and peritubular capillaries. Rejection-free survival was significantly longer in Group 1 (p < 0.05). CONCLUSIONS: The absence of expression of Neu5Gc on pig kidney grafts is associated with increased binding of baboon antibodies to pig endothelium and reduced graft survival.

Evidence suggesting that deletion of expression of N-glycolylneuraminic acid (Neu5Gc) in the organ-source pig is associated with increased antibody-mediated rejection of kidney transplants in baboons.

Pigs deficient in three glycosyltransferase enzymes (triple-knockout [TKO] pigs) and expressing "protective" human transgenes are likely sources of organs for transplantation into human recipients. Testing of human sera against red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs) from TKO pigs has revealed minimal evidence of natural antibody binding. However, unlike humans, baboons exhibit natural antibody binding to TKO pig cells. The xenoantigen specificities of these natural antibodies are postulated to be one or more carbohydrate moieties exposed when N-glycolylneuraminic acid (Neu5Gc) is deleted. The aim of this study was to compare the survival of renal grafts in baboons from pigs that either expressed Neu5Gc (GTKO pigs; Group1, n = 5) or did not express Neu5Gc (GTKO/CMAHKO [DKO] or TKO pigs; Group2, n = 5). An anti-CD40mAb-based immunosuppressive regimen was administered in both groups. Group1 kidneys functioned for 90-260 days (median 237, mean 196 days), with histopathological features of antibody-mediated rejection in two kidneys. Group2 kidneys functioned for 0-183 days (median 35, mean 57), with all of the grafts exhibiting histologic features of antibody-mediated rejection. These findings suggest that the absence of expression of Neu5Gc on pig kidneys impacts graft survival in baboon recipients.

Pig kidney xenotransplantation: Progress toward clinical trials.

Pig organ xenotransplantation offers a solution to the shortage of deceased human organs for transplantation. The pathobiological response to a pig xenograft is complex, involving antibody, complement, coagulation, inflammatory, and cellular responses. To overcome these barriers, genetic manipulation of the organ-source pigs has largely been directed to two major aims-(a) deletion of expression of the known carbohydrate xenoantigens against which humans have natural (preformed) antibodies, and (b) transgenic expression of human protective proteins, for example, complement- and coagulation-regulatory proteins. Conventional (FDA-approved) immunosuppressive therapy is unsuccessful in preventing an adaptive immune response to pig cells, but blockade of the CD40:CD154 costimulation pathway is successful. Survival of genetically engineered pig kidneys in immunosuppressed nonhuman primates can now be measured in months. Non-immunological aspects, for example, pig renal function, a hypovolemia syndrome, and rapid growth of the pig kidney after transplantation, are briefly discussed. We suggest that patients on the wait-list for a deceased human kidney graft who are unlikely to receive one due to long waiting times are those for whom kidney xenotransplantation might first be considered. The potential risk of infection, public attitudes to xenotransplantation, and ethical, regulatory, and financial aspects are briefly addressed.

Clinical Pig Kidney Xenotransplantation: How Close Are We?

Patients with ESKD who would benefit from a kidney transplant face a critical and continuing shortage of kidneys from deceased human donors. As a result, such patients wait a median of 3.9 years to receive a donor kidney, by which time approximately 35% of transplant candidates have died while waiting or have been removed from the waiting list. Those of blood group B or O may experience a significantly longer waiting period. This problem could be resolved if kidneys from genetically engineered pigs offered an alternative with an acceptable clinical outcome. Attempts to accomplish this have followed two major paths: deletion of pig xenoantigens, as well as insertion of "protective" human transgenes to counter the human immune response. Pigs with up to nine genetic manipulations are now available. In nonhuman primates, administering novel agents that block the CD40/CD154 costimulation pathway, such as an anti-CD40 mAb, suppresses the adaptive immune response, leading to pig kidney graft survival of many months without features of rejection (experiments were terminated for infectious complications). In the absence of innate and adaptive immune responses, the transplanted pig kidneys have generally displayed excellent function. A clinical trial is anticipated within 2 years. We suggest that it would be ethical to offer a pig kidney transplant to selected patients who have a life expectancy shorter than the time it would take for them to obtain a kidney from a deceased human donor. In the future, the pigs will also be genetically engineered to control the adaptive immune response, thus enabling exogenous immunosuppressive therapy to be significantly reduced or eliminated.

The development of artificial livers.

PURPOSE OF REVIEW: While liver transplantation is an established treatment for liver failure, the number of patients with liver failure amenable to such intervention far outnumbers the donor supply of livers. Technologies serving to bridge this gap are required. Artificial livers may serve as an alternative. In this review, we discuss the development of artificial liver technologies. RECENT FINDINGS: The accrued clinical data suggest that current liver assist devices may serve a role in specific liver diseases, but for the most part no survival benefit has been demonstrated. More clinical trials are expected to elucidate their utilization. Simultaneously, recent advances in materials and tissue engineering are allowing for exciting developments for novel artificial livers. SUMMARY: As there continues to be more clinical data regarding the use of current liver devices, new intricate artificial liver technologies, with the use of sophisticated three-dimensional materials, are being developed that may help improve outcomes of liver failure patients.

The final obstacle to successful pre-clinical xenotransplantation?

Genetically engineered pigs are now available for xenotransplantation in which all three known carbohydrate xenoantigens, against which humans have natural antibodies, have been deleted (triple-knockout [TKO] pigs). Furthermore, multiple human transgenes have been expressed in the TKO pigs, all of which are aimed at protecting the cells from the human immune response. Many human sera demonstrate no or minimal antibody binding to, and little or no cytotoxicity of, cells from these pigs, and this is associated with a relatively low T-cell proliferative response. Unfortunately, baboons and other Old World NHPs have antibodies against TKO pig cells, apparently directed to a fourth xenoantigen that appears to be exposed after TKO. In our experience, most, if not all, humans do not have natural antibodies against this fourth xenoantigen. This discrepancy between NHPs and humans is providing a hurdle to successful translation of pig organ transplantation into the clinic, and making it difficult to provide pre-clinical data that support initiation of a clinical trial. The potential methods by which this obstacle might be overcome are discussed. We conclude that, whatever currently available genetically engineered pig is selected for the final pre-clinical studies, this may not be the optimal pig for clinical trials.

Examining the Biosynthesis and Xenoantigenicity of Class II Swine Leukocyte Antigen Proteins.

Genetically engineered pig organs could provide transplants to all patients with end-stage organ failure, but Ab-mediated rejection remains an issue. This study examines the class II swine leukocyte Ag (SLA) as a target of epitope-restricted Ab binding. Transfection of individual α- and ß-chains into human embryonic kidney cells resulted in both traditional and hybrid class II SLA molecules. Sera from individuals on the solid organ transplant waiting list were tested for Ab binding and cytotoxicity to this panel of class II SLA single-Ag cells. A series of elution studies from an SLA-DQ cell line were performed. Our results indicate that human sera contain Abs specific for and cytotoxic against class II SLA. Our elution studies revealed that sera bind the SLA-DQ molecule in an epitope-restricted pattern. Site-specific mutation of one of these epitopes resulted in statistically decreased Ab binding. Humans possess preformed, specific, and cytotoxic Abs to class II SLA that bind in an epitope-restricted fashion. Site-specific epitope mutagenesis may decrease the Ab binding of highly sensitized individuals to pig cells.

Paediatric xenotransplantation clinical trials and the right to withdraw.

Clinical trials of xenotransplantation (XTx) may begin early in the next decade, with kidneys from genetically modified pigs transplanted into adult humans. If successful, transplanting pig hearts into children with advanced heart failure may be the next step. Typically, clinical trials have a specified end date, and participants are aware of the amount of time they will be in the study. This is not so with XTx. The current ethical consensus is that XTx recipients must consent to lifelong monitoring. While this presents challenges to the right to withdraw in the adult population, additional and unanswered questions also linger in the paediatric population. In paediatric XTx, parents or guardians consent not only to the initial treatment of the child but also to lifelong monitoring, thus making a decision whose consequences will remain present as the child develops the capacity for assent, and finally the capacity for informed consent or refusal. This article presents and evaluates unanswered paediatric ethical questions in regard to the right to withdraw from XTx follow-up in the paediatric population.

Mitigating Racial and Sex Disparities in Access to Living Donor Kidney Transplantation: Impact of the Nation's Longest Single-center Kidney Chain.

OBJECTIVE: In this study, we sought to assess likelihood of living donor kidney transplantation (LDKT) within a single-center kidney transplant waitlist, by race and sex, after implementation of an incompatible program. SUMMARY BACKGROUND DATA: Disparities in access to LDKT exist among minority women and may be partially explained by antigen sensitization secondary to prior pregnancies, transplants, or blood transfusions, creating difficulty finding compatible matches. To address these and other obstacles, an incompatible LDKT program, incorporating desensitization and kidney paired donation, was created at our institution. METHODS: A retrospective cohort study was performed among our kidney transplant waitlist candidates (n = 8895). Multivariable Cox regression was utilized, comparing likelihood of LDKT before (era 1: 01/2007-01/2013) and after (era 2: 01/2013-11/2018) implementation of the incompatible program. Candidates were stratified by race [white vs minority (nonwhite)], sex, and breadth of sensitization. RESULTS: Program implementation resulted in the nation's longest single-center kidney chain, and likelihood of LDKT increased by 70% for whites [adjusted hazard ratio (aHR) 1.70; 95% confidence interval (CI), 1.46-1.99] and more than 100% for minorities (aHR 2.05; 95% CI, 1.60-2.62). Improvement in access to LDKT was greatest among sensitized minority women [calculated panel reactive antibody (cPRA) 11%-49%: aHR 4.79; 95% CI, 2.27-10.11; cPRA 50%-100%: aHR 4.09; 95% CI, 1.89-8.82]. CONCLUSIONS: Implementation of an incompatible program, and the resulting nation's longest single-center kidney chain, mitigated disparities in access to LDKT among minorities, specifically sensitized women. Extrapolation of this success on a national level may further serve these vulnerable populations.

What's hot, what's new: Report from the American Transplant Congress 2018.

The American Transplant Congress (ATC) 2018 event brought over 5000 attendees to Seattle, WA in June 2018. As the joint meeting of the American Society of Transplant Surgeons (ASTS) and the American Society of Transplantation (AST), the Congress provides exposures to cutting-edge scientific research findings for a diverse mix of physicians, surgeons, scientists, nurses, organ procurement personnel, advanced transplant providers, pharmacists, administrators, and other transplant professionals. The 5-day event featured nearly 1800 abstracts, over 500 oral presentations, and more than 1200 poster presentations, all delivered in a way that encouraged the exchange of new clinical and scientific information and supported an interchange of opinions regarding care management and socioeconomic, ethical, and regulatory issues relevant to organ and tissue transplantation. We present here the outstanding abstracts presented at ATC2018 divided into 3 categories of basic, translational, and clinical research.

Xenoantigen Deletion and Chemical Immunosuppression Can Prolong Renal Xenograft Survival.

OBJECTIVE: Xenotransplantation using pig organs could end the donor organ shortage for transplantation, but humans have xenoreactive antibodies that cause early graft rejection. Genome editing can eliminate xenoantigens in donor pigs to minimize the impact of these xenoantibodies. Here we determine whether an improved cross-match and chemical immunosuppression could result in prolonged kidney xenograft survival in a pig-to-rhesus preclinical model. METHODS: Double xenoantigen (Gal and Sda) knockout (DKO) pigs were created using CRISPR/Cas. Serum from rhesus monkeys (n = 43) was cross-matched with cells from the DKO pigs. Kidneys from the DKO pigs were transplanted into rhesus monkeys (n = 6) that had the least reactive cross-matches. The rhesus recipients were immunosuppressed with anti-CD4 and anti-CD8 T-cell depletion, anti-CD154, mycophenolic acid, and steroids. RESULTS: Rhesus antibody binding to DKO cells is reduced, but all still have positive CDC and flow cross-match. Three grafts were rejected early at 5, 6, and 6 days. Longer survival was achieved in recipients with survival to 35, 100, and 435 days. Each of the 3 early graft losses was secondary to IgM antibody-mediated rejection. The 435-day graft loss occurred secondary to IgG antibody-mediated rejection. CONCLUSIONS: Reducing xenoantigens in donor pigs and chemical immunosuppression can be used to achieve prolonged renal xenograft survival in a preclinical model, suggesting that if a negative cross-match can be obtained for humans then prolonged survival could be achieved.

Two Cases and a Review of Graft-Versus-Host Disease and the Role of Hepatitis C Treatment in Liver Transplant Patients.

Graft-versus-host disease (GvHD) is a rare but fatal complication after solid organ transplantation arising in 1% to 2% of cases. We report 2 cases of GvHD after orthotopic liver transplantation. Both patients had a history of hepatitis C virus (HCV) infection prior to transplantation. Both cases presented between 1 and 4 months after transplantation with rash, pancytopenia, and/or diarrhea. Our second case also developed oral and ocular manifestations after liver transplantation, which are more commonly described after stem cell transplantation. Diagnosis in both cases was made by clinical presentation in conjunction with histopathology and flow cytometry. Both patients were treated by increasing immunosuppression with tacrolimus and high-dose steroids. Response to treatment differed based on the degree of pancytopenia. Our case report is distinguished by several factors such as the context of GvHD presentation and the role of HCV treatment. Diagnosis of GvHD is difficult and often delayed due to nonspecific presentation that overlaps with other conditions. Furthermore, the relation between HCV treatment and potential initiation of GvHD in solid organ transplant patients is unclear.

A SEER Database Analysis of the Survival Advantage of Transarterial Chemoembolization for Hepatocellular Carcinoma: An Underutilized Therapy.

PURPOSE: To measure transarterial chemoembolization utilization and survival benefit among patients with hepatocellular carcinoma (HCC) in the Surveillance, Epidemiology, and End Results (SEER) patient population. MATERIALS AND METHODS: A retrospective study identified 37,832 patients with HCC diagnosed between 1991 and 2011. Survival was estimated by Kaplan-Meier method and compared by log-rank test. Propensity-score matching was used to address an imbalance of covariates. RESULTS: More than 75% of patients with HCC did not receive any HCC-directed treatment. Transarterial chemoembolization was the most common initial therapy (15.9%). Factors associated with the use of chemoembolization included younger age, more HCC risk factors, more comorbidities, higher socioeconomic status, intrahepatic tumor, unifocal tumor, vascular invasion, and smaller tumor size (all P < .001). Median survival was improved in patients treated with chemoembolization compared with those not treated with chemoembolization (20.1 vs 4.3 mo; P < .0001). Similar findings were demonstrated in propensity-scoring analysis (14.5 vs 4.2 mo; P < .0001) and immortal time bias sensitivity analysis (9.5 vs 3.6 mo; P < .0001). There was a significantly improved survival hazard ratio (HR) in patients treated with chemoembolization (HR, 0.42; 95% confidence interval, 0.39-0.45). CONCLUSIONS: Patients with HCC treated with transarterial chemoembolization experienced a significant survival advantage compared with those not treated with transarterial chemoembolization. More than 75% of SEER/Medicare patients diagnosed with HCC received no identifiable oncologic treatment. There is a significant public health need to increase awareness of efficacious HCC treatments such as transarterial chemoembolization.