Impact of waiting time on post-transplant survival for recipients with hepatocellular carcinoma: A natural experiment randomized by blood group

Background & Aims

When listing for liver transplantation, one can transplant as soon as possible or introduce a test-of-time to better select patients, as the tumor's biological behavior is observed. Knowing the degree of harm caused by time itself is essential to advise patients and decide on the maximum duration of the test-of-time. Therefore, we investigated the causal effect of waiting time on post-transplant survival for patients with hepatocellular carcinoma.

Methods

We analyzed the UNOS-OPTN dataset and exploited a natural experiment created by blood groups. Relations between variables and assumptions were described in a causal graph. Selection bias was addressed by inverse probability weighting. Confounding was avoided using instrumental variable analysis, with an additive hazards model in the second stage. The causal effect was evaluated by estimating the difference in 5-year overall survival if all patients waited 2 months instead of 12 months. Upper bounds of the test-of-time were evaluated for probable scenarios by means of simulation.

Results

The F-statistic of the first stage was 86.3. The effect of waiting 12 months vs. 2 months corresponded with a drop in overall survival rate of 5.07% (95% CI 0.277-9.69) and 8.33% (95% CI 0.47-15.60) at 5- and 10-years post-transplant, respectively. The median survival dropped by 3.41 years from 16.21 years (95% CI 15.98-16.60) for those waiting 2 months to 12.80 years (95% CI 10.72-15.90) for those waiting 12 months.

Conclusions

From a patient's perspective, the choice between ablate-and-wait vs. immediate transplantation is in favor of immediate transplantation. From a policy perspective, the extra waiting time can be used to increase the utility of scarce donor livers. However, the duration of the test-of-time is bounded, and it likely should not exceed 8 months.

Impact and implications

When listing patients with liver cancer for transplantation, it is unclear whether a test-of-time or immediate transplantation offer better outcomes at the population level. In this study, we found that increased liver transplant waiting times are detrimental in patients with liver cancer. Furthermore, our simulation showed that a pre-operative observational period can be useful to ensure good donor liver allocation, but that its duration should not exceed 8 months.

Outcomes after heart transplantation in patients who have undergone a bridge-to-bridge strategy

Objectives

We compared posttransplant outcomes between patients bridged from temporary mechanical circulatory support to durable left ventricular assist device before transplant (bridge-to-bridge [BTB] strategy) and patients bridged from temporary mechanical circulatory support directly to transplant (bridge-to-transplant [BTT] strategy).

Methods

We identified adult heart transplant recipients in the Organ Procurement and Transplantation Network database between 2005 and 2020 who were supported with extracorporeal membrane oxygenation, intra-aortic balloon pump, or temporary ventricular assist device as a BTB or BTT strategy. Kaplan-Meier survival analysis and Cox regressions were used to assess 1-year, 5-year, and 10-year survival. Posttransplant length of stay and complications were compared as secondary outcomes.

Results

In total, 201 extracorporeal membrane oxygenation (61 BTB, 140 BTT), 1385 intra-aortic balloon pump (460 BTB, 925 BTT), and 234 temporary ventricular assist device (75 BTB, 159 BTT) patients were identified. For patients supported with extracorporeal membrane oxygenation, intra-aortic balloon pump, or temporary ventricular assist device, there were no differences in survival between BTB and BTT at 1 and 5 years posttransplant, as well as 10 years posttransplant even after adjusting for baseline characteristics. The extracorporeal membrane oxygenation BTB group had greater rates of acute rejection (32.8% vs 13.6%; P = .002) and lower rates of dialysis (1.6% vs 21.4%; P < .001). For intra-aortic balloon pump and temporary ventricular assist device patients, there were no differences in posttransplant length of stay, acute rejection, airway compromise, stroke, dialysis, or pacemaker insertion between BTB and BTT recipients.

Conclusions

BTB patients have similar short- and midterm posttransplant survival as BTT patients. Future studies should continue to investigate the tradeoff between prolonged temporary mechanical circulatory support versus transitioning to durable mechanical circulatory support.

Assessment of U.S. heart transplantation equity as a function of race: Observational analyses of the OPTN database

Background

Racial disparities in heart transplantation (HT) outcomes are suspected but uncertain. The additional impact of a recent change in donor allocation on disparities in HT in the United States (US) is unknown. We hypothesize racial disparities in HT are present and may be worsened by new allocation practices.

Methods

Cohort: Adults listed for HT before and after a heart allocation policy change (Era 1: Oct 18^th, 2015 - Oct 18^th, 2018, Era 2: Oct 18^th, 2018-June 30, 2021). The primary outcome was the rate of HT by race (Black vs. White), assessed using multivariable competing risk analysis (compete: waitlist removal for death or clinical deterioration). Final adjusted models included co-morbidities, SES and community-level Social Determinants of Health. The secondary outcome was waitlist removal for death or clinical deterioration.

Results

Of 17,384 waitlist candidates (Era 1: 9,150, Era 2: 8,234), Black waitlist candidates had a lower rate of HT compared to White waitlist candidates in Era 1 (adjusted HR 0·90, 95 % CI 0·84-0·97, p = 0·0053) and in Era 2 (adjusted HR 0·81, 95 % CI 0·75-0·88, p <0·0001, era race interaction p=0·056). The rate of waitlist removal for death or deterioration was similar between races in Era 1 (adjusted HR 0·92, 95 % 0·77-1·1, p = 0·38), but increased for Black candidates in Era 2 (adjusted HR 1·34, 95 % CI 1·09-1·65, p = 0·0054, era race interaction p = 0·0051).

Interpretation

Both the measured rate of transplantation and rate of delisting for death or clinical deterioration have worsened for Black compared to White waitlist candidates under the new allocation system. Causes for these disparities require further study.

Funding

University of Minnesota Department of Cardiology funds.

Use of Computed Tomography Coronary Calcium Score for Coronary Artery Disease Risk Stratification During Liver Transplant Evaluation

Background

End-stage liver disease (ESLD) is not considered a risk factor for atherosclerotic cardiovascular disease (ASCVD). However, lifestyle characteristics commonly associated with increased ASCVD risk are highly prevalent in ESLD. Emerging literature shows a high burden of asymptomatic coronary artery disease (CAD) in patients with ESLD and a high ASCVD risk in liver transplantation (LT) recipients. Coronary artery calcium score (CAC) is a noninvasive test providing reliable CAD risk stratification. We implemented an LT evaluation protocol with CAC playing a central role in triaging and determining the need for further CAD assessment. Here, we inform our results from this early experience.

Methods

Patients with ESLD referred for LT evaluation were prospectively studied. We compared accuracy of CAC against that of CAD risk factors/scores, troponin I, dobutamine stress echocardiogram (DSE), and single-photon emission computed tomography (SPECT) to detect coronary stenosis ≥70 (CAD ≥ 70) per left heart catheterization (LHC). Thirty-day post-LT cardiac outcomes were also analyzed.

Results

One hundred twenty-four of 148 (84%) patients underwent CAC, 106 (72%) DSE/SPECT, and 50 (34%) LHC. CAC ≥ 400 was found in 35 (28%), 100 to 399 in 17 (14%), and <100 in 72 (58%). LHC identified CAD ≥ 70% in 8 of 29 (28%), 2 of 9 (22%), and 0 of 4, respectively. Two acute coronary syndromes occurred after LT in a patient with CAC 811 (CAD < 70%), and one with CAC 347 (CAD ≥ 70%). No patients with CAC < 100 presented with acute coronary syndrome after LT. When using CAD ≥ 70% as primary endpoint of LT evaluation, CAC ≥ 346 was the only test showing predictive usefulness (negative predictive value 100%).

Conclusions

CAC is a promising tool to guide CAD risk stratification and need for LHC during LT evaluation. Patients with a CAC < 100 can safely undergo LT without the need for LHC or cardiac stress testing, whereas a CAC < 346 accurately rules out significant CAD stenosis (≥70%) on LHC, outperforming other CAD risk-stratification strategies.

The influence of equitable access policies and socioeconomic factors on post-liver transplant survival

BACKGROUND

Survival following liver transplant (LT) is influenced by a variety of factors, including donor risk factors and recipient disease burden and co-morbidities. It is difficult to separate these effects from those of socioeconomic factors, such as income or insurance. The United Network for Organ Sharing (UNOS) created equitable access policies, such as Share 35, to ensure that organs are distributed to individuals with greatest medical need; however, the effect of Share 35 on disparities in post-LT survival is not clear. This study aimed to (1) characterize associations between post-transplant survival and race and ethnicity, income, insurance, and citizenship status, when adjusted for other clinical and demographic factors that may influence survival, and (2) determine if the direction of associations changed after Share 35.

METHODS

A retrospective, cohort study of adult LT recipients (n = 83,254) from the UNOS database from 2005 to 2019 was conducted. Kaplan-Meier survival graphs and stepwise multivariate cox-regression analyses were performed to characterize the effects of socioeconomic status on post-LT survival, adjusted for recipient and donor characteristics, across the time period and after Share 35.

FINDINGS

Male sex (HR: 0.93 (95% CI: 0.90-0.96)), private insurance (0.91 (0.88-0.94)), income (0.82 (0.79-0.85)), U.S. citizenship, and Asian (0.81 (0.75-0.88)) or Hispanic (0.82 (0.79-0.86)) race and ethnicity were associated with higher post-transplant survival, after adjustment for clinical and demographic factors (Table 3). These associations were found across the entire time period studied and many persisted after the implementation of Share 35 in 2013 (Table 3; male sex (0.84 (0.79-0.90)), private insurance (0.94 (0.89-1.00)), income (0.82 (0.77-0.89)), and Asian (0.87 (0.73-1.02)) or Hispanic (0.88 (0.81-0.96)) race and ethnicity).

INTERPRETATION

Recipients' socioeconomic factors at time of transplant may impact long-term post-transplant survival, and a single policy may not significantly alter these structural health inequalities.

FUNDING

None.

US deceased kidney transplantation: Estimated GFR, donor age and KDPI association with graft survival

BACKGROUND

Despite a significant shortage of kidneys for transplantation in the US, kidneys from older deceased donors are infrequently transplanted. This is primarily over concern of graft quality and transplant durability.

METHODS

The US national transplant database (2000-2018) was assessed for deceased donor kidney transplant patient and graft survival, graft durability and stratified by donor age (<65 years>), Kidney Donor Profile Index (KDPI) and estimated glomerual filtration rate (GFR) one year post-transplantation (eGFR-1) were calculated.

FINDINGS

Recipients of kidneys transplanted from deceased donors >65 years had a lower eGFR-1, (median 39 ml/min) than recipients of younger donor kidneys (median 54 ml/min). However, death-censored graft survival, stratified by eGFR-1, demonstrated similar survival, irrespective of donor age or KDPI. The durability of kidney survival decreases as the achieved eGFR-1 declines. KDPI has a poor association with eGFR-1 and lesser for graft durability. While recipients of kidneys > 65 years had a higher one year mortality than younger kidney recipients, recipients of kidneys > 65 years and an eGFR-1 <30 ml/min, had a lower survival than an untransplanted waitlist cohort (p<0.001).

INTERPRETATION

The durability of kidney graft survival after transplantation was associated with the amount of kidney function gained through the transplant (eGFR-1) and the rate of graft loss (return to dialysis) was not significantly associated with donor age. 24.9% of recipients of older donor kidneys failed to achieve sufficient eGFR-1 providing a transplant survival benefit. While there is significant benefit from transplanting older kidneys, better decision-making tools are required to avoid transplanting kidneys that provide insufficient renal function.

FUNDING

None.

Ethnicity and Insurance-Specific Disparities in the Model for End-Stage Liver Disease Score at Time of Liver Transplant Waitlist Registration and its Impact on Mortality

BACKGROUND AND AIMS

Disparities in timely referral to liver transplantation (LT) evaluation persist. We aim to examine race/ethnicity and insurance-specific differences in the Model for End-Stage Liver Disease (MELD) score at time of waitlist (WL) registration and its impact on WL survival.

METHODS

We retrospectively evaluated U.S. adults listed for LT using 2005-2018 United Network for Organ Sharing LT registry. Multiple linear regression methods examined factors associated with MELD at listing, and Fine-Gray competing risks regression were used to analyze WL mortality.

RESULTS

Among 144,163 WL registrants (median age = 56 years, 65.3% male, 56.4% private insurance, 23.3% Medicare, 15.7% Medicaid), mean WL MELD at listing was higher in African Americans versus non-Hispanic whites (2.57 points higher, 95%CI: 2.40-2.74, P < 0.001). Compared with patients with private insurance, adjusted mean WL MELD was higher among those with no insurance, Medicare, or Medicaid (P < 0.001 for all). After correcting for differences in MELD at listing, Asians had lower risk of WL death versus non-Hispanic whites (subhazard ratio (SHR): 0.92, 95% CI: 0.86-1.00, P = 0.04), but no difference was observed in African Americans or Hispanics. Compared with patients with private insurance, higher risk of WL death was observed in patients with no insurance (SHR: 1.33, 95%CI: 1.14-1.56, P < 0.001), Medicare (SHR: 1.20, 95%CI: 1.16-1.25, P < 0.001), or Medicaid (SHR: 1.22, 95%CI: 1.17-1.27, P < 0.001).

CONCLUSION

Higher MELD scores at listing among African Americans did not translate into increased WL mortality. Patients with Medicare, Medicaid, or uninsured had significantly higher WL mortality than privately insured patients, even after correcting for disparities in MELD scores at listing.

Identifying Patterns of Adverse Events of Solid Organ Transplantation Through Departmental Case Reviews

The best approach to adverse-event review in solid organ transplantation is unknown. We initiated a departmental case review (DCR) method based on root-cause analysis methods in a high-volume multiorgan transplant center. We aimed to describe this process and its contributions to process improvement.

Methods

Using our prospectively maintained transplant center quality portfolio, we performed a retrospective review of a 30-month period (October 26, 2015, to May 14, 2018) after DCR-process initiation at our center. We used univariate statistics to identify counts of adverse events, DCRs, death and graft-loss events, and quality improvement action-plan items identified during case review. We evaluated variation among organ groups in action-plan items, associated phase of transplant care, and quality improvement theme.

Results

Over 30 months, we performed 1449 transplant and living donor procedures with a total of 45 deaths and 31 graft losses; 91 DCRs were performed (kidney transplant n=43; liver transplant n=24; pancreas transplant n=10; heart transplant n=6; lung transplant n=3; living donor n=5). Seventy-nine action-plan items were identified across improvement domains, including errors in clinical decision making, communication, compliance, documentation, selection, waitlist management, and administrative processes. Median time to review was 83 days and varied significantly by program. Median time to action-plan item completion was 9 weeks. Clinical decision making in the pretransplant phase was identified as an improvement opportunity in all programs.

Conclusions

DCRs provide a robust approach to transplant adverse-event review. Quality improvement targets and domains may vary based on adverse-event profiles.

The Changing Face of Hepatocellular Carcinoma: Forecasting Prevalence of Nonalcoholic Steatohepatitis and Hepatitis C Cirrhosis

BACKGROUND/OBJECTIVES

The purpose of this research is to analyze the past and forecast the future prevalence of Hepatitis C Virus (HCV) and Nonalcoholic Steatohepatitis (NASH) and their respective contribution to Hepatocellular Carcinoma (HCC) incidence in the setting of novel anti-viral agents and rising obesity rates in the United States.

METHODS

Existing data of HCV and NASH prevalence in the United States utilizing the National Health and Nutrition Examination Survey (NHANES) and Organ Procurement and Transplantation Network (OPTN) was collected and analyzed to project future prevalence trends.

RESULTS

Prevalence of NASH and HCV are expected to increase and decline respectively over the next two decades with alcoholic cirrhosis expected to stay relatively unchanged. The estimated prevalence of NASH equaled and overtook the projected prevalence of HCV in 2007 at approximately 3 million persons. Estimates of NASH's contribution to HCC overtook HCV-HCC in 2015 at an approximately 25 million persons. Projection models suggest HCV prevalence declining to 1 million active cases by 2025, while NASH potentially increases to 17-42 million depending on a linear or exponential trendline. Projections of NASH-HCC similarly outpace HCV-HCC by 2025 with 45 million or 106 million (linear, exponential) versus 18 million persons respectively.

CONCLUSIONS

The future prevalence of HCV and NASH are expected to become further divergent with NASH emerging as the major contributor of cirrhosis and HCC in the United States.

Donor Factors Including Donor Risk Index Predict Fibrosis Progression, Allograft Loss, and Patient Survival following Liver Transplantation for Hepatitis C Virus

BACKGROUND

The utilization of liver transplantation (LT) is limited by the availability of suitable organs. This study aimed to assess the impact of the donor risk index (DRI) and other donor characteristics on fibrosis progression, graft, and patient survival in hepatitis C virus (HCV)-infected LT recipients.

METHODS

HCV-infected LT recipients who had at least 2 post-LT protocol liver biopsy specimens available were included. Hazard ratio for bivariate analysis was computed using Cox proportional hazard regression analysis.

RESULTS

Of 312 recipients, 26.6% died over a median follow-up of 58.5 months (95% CI: 46.5-67.3). Fourteen patients underwent re-transplantation. Mean time to graft failure was 84.3 months, median follow-up: 59 months, 95% CI (48.2, 68.3). DRI >1.5 was significantly associated with patient and graft survival (P = 0.04). Of the subset of 104 individuals who underwent histological analysis, 67.3% progressed to ≥F2. On multivariate analysis, significant donor-specific predictors of fibrosis progression were: donor age >50 years and DRI >1.7.

CONCLUSIONS

(1) Fibrosis progression in HCV-infected LT recipients is strongly associated with donor characteristics, specifically donor age and DRI. (2) DRI, an objective measure of donor quality, appears to correlate both with rate of histological progression and overall patient/graft survival.

Liver Transplantation: East versus West

Liver transplantation (LT) has evolved rapidly since the first successful liver transplant performed in1967. Despite a humble beginning, this procedure gained widespread acceptance in the western world as a suitable option for patients with end stage liver disease (ESLD) by the beginning of the 1980s. At present, approximately 25,000 liver transplants are being performed worldwide every year with approximately 90% one year survival. The techniques of living donor liver transplantation (LDLT) developed in East Asia in the 1990s to overcome the shortage of suitable grafts for children and scarcity of deceased donors. While deceased donor liver transplantation (DDLT) constitutes more than 90% of LT in the western world, in India and other Asian countries, most transplants are LDLT. Despite the initial disparity, outcomes following LDLT in eastern countries have been quite satisfactory when compared to the western programs. The etiologies of liver failure requiring LT vary in different parts of the world. The commonest etiology for acute liver failure (ALF) leading to LT is drugs in the west and acute viral hepatitis in Asia. The most common indication for LT due to ESLD in west is alcoholic cirrhosis and hepatitis C virus (HCV), while hepatitis B virus (HBV) predominates in the east. There is a variation in prognostic models for assessing candidature and prioritizing organ allocation across the world. Model for end-stage liver disease (MELD) is followed in United States and some European centers. Other European countries rely on the Child-Turcotte-Pugh (CTP) score. Some parts of Asia still follow chronological order of listing. The debate regarding the best model for organ allocation is far from over.