The Lung Allocation Score and Its Relevance

Impact of donor age ≥65 years on graft survival in large lung transplant cohorts

BACKGROUND

Although the demand for allografts continuously surpasses the supply, the majority of lungs offered for transplant are declined based on various factors, including donor age. This in turn sustains the wait-list mortality of patients with end-stage pulmonary disease.

METHODS

In this single-center, observational cohort study, we investigated the impact of donor age on graft survival. We additionally compared our center's data to data reported to the International Society for Heart and Lung Transplantation (ISHLT) Thoracic Organ Transplant Registry. Kaplan-Meier method was used to describe overall graft survival. Multivariate Cox proportional hazards regression was used to assess clinical features associated with graft loss.

RESULTS

Between January 2010 and December 2023, Alfred performed 1,101 single and double lung transplants and the combined ISHLT cohort totaled 32,200 transplants. At Alfred, grafts originating from donors ≥65 years were used in 13.3% of lung transplant cases and univariate analysis showed no impact of donor age ≥65 on graft survival (hazard ratio [HR] 0.86, p = 0.34). In the combined cohort, North America had a lower proportion of donors aged ≥65 years compared to Europe and the Alfred (2.4% vs 9.8% vs 13.3%, p < 0.001). The univariate analysis showed a negative impact of donor age ≥65 on graft survival (HR 1.16, p < 0.001). However, this did not hold in a multivariate model (HR 1.06, p = 0.298) when adjusted for center experience and recipient characteristics.

CONCLUSIONS

Donor age might impact outcomes to a lesser degree than previously suggested. Therefore, appropriately assessed age-extended lungs should be routinely considered for lung transplantation.

Hospital-free days in the first year after lung transplantation and subsequent survival

Background

Complications occurring during the first postoperative year after lung transplantation increase the risk of long-term mortality. These events often lead to prolonged and repeated hospitalizations. We sought to assess the relationship between days outside the hospital or hospital-free days (HFD) during the first post-transplant year among 1-year survivors and subsequent retransplant-free survival.

Methods

In a single-center study, we derived total inpatient days (initial transplant episode, readmission, and emergency room/observation) from the electronic medical record of lung transplant recipients who survived 1 year. The cohort was divided into HFD quartiles and Kaplan-Meier curves of subsequent transplant-free survival were compared with log-rank analysis. A Cox proportional hazards model was used to test the association of HFD with outcome and adjusted for selected variables.

Results

Among 238 patients, 42 deaths and 2 retransplants occurred after a median of 3.6 years post-transplant. The median HFD was 341 (interquartile range: 324, 348). Estimated transplant-free survival at 3 and 5 years post-transplant in the lowest quartile of HFD (79% and 56%, respectively) was considerably worse compared with the first quartile (98% and 94%; p < 0.01). Fewer HFD were associated with subsequent death or retransplant [hazard ratio: 0.90 (95% confidence interval: 0.85, 0.94; p < 0.001) for each 10-day increase] and remained significant after adjusting for several potentially confounding variables.

Conclusions

HFD during the first year after lung transplantation is a predictor of subsequent long-term outcomes and may be a useful surrogate marker for clinical trials during the early postoperative period.

Concomitant Heart and Lung Surgery During Lung Transplantation

INTRODUCTION

There is limited data concerning concomitant cardiac and lung surgery outcomes during lung transplantation (LTx). While some evidence suggests that cardiac surgery during LTx has no significant impact on surgical outcomes, scarce data examines the role of concomitant lung surgery (CLS). This study compares the survival outcomes of concomitant cardiac and lung surgeries during LTx.

METHODS

A retrospective analysis of all single and double LTx patients from March 2012 to June 2023 at a single center was performed (n = 1099). Patients were stratified into three concomitant surgical groups: concomitant cardiac surgery (CCS), CLS, and no concomitant surgeries. Groups were compared on recipient demographics, diagnosis, and surgical intervention using analysis of variance and chi-square tests. Survival (5 y) was analyzed using Kaplan-Meier curves, log-rank test, and univariable Cox proportional hazard model where P value <0.05 was considered significant.

RESULTS

In total, 1099 patients were analyzed in this study; 965 had no concomitant surgery, 100 had CCS (mode: coronary artery bypass grafting, n = 75), and 34 had CLS (mode: lung volume reduction surgery, n = 14). Between the three surgical groups, there was no significant difference in body mass index (P = 0.091), total ischemic time (P = 0.194), induction (P = 0.140), or cause of death (P = 0.240). Lung allocation score and length of stay were significantly higher in the concomitant surgical groups, especially the CLS group when compared to the no concomitant surgery group (P = 0.002, P = 004). Patients with no concomitant surgery had a higher incidence of single LTx and off-pump utilization than concomitant surgical groups (P < 0.001). Kaplan-Meier curves and log-rank tests found no significant difference in survival between groups (P = 0.849). This result is supported by Cox proportional hazard model with no significant difference in mortality risk between the CCS group (P = 0.522) and CLS group (P = 0.936) compared to no concomitant surgery during LTx.

CONCLUSIONS

Our study provides promising data indicating that individuals undergoing concomitant heart or lung surgery during LTx have similar survival outcomes to those exclusively undergoing LTx. These results highlight the potential advantages of utilizing LTx to address concurrent thoracic surgical needs, such as coronary revascularization. This holds implications for optimizing patient care and decision-making when complex thoracic interventions are necessary.

Transplanting candidates with stacked risks negatively affects outcomes

BACKGROUND

Lung transplant (LT) centers are increasingly evaluating patients with multiple risk factors for adverse outcomes. The effects of these stacked risks remains unclear. Our aim was to determine the relationship between the number of comorbidities and post-transplant outcomes.

METHODS

We performed a retrospective cohort study using the National Inpatient Sample (NIS) and UNOS Starfile (USF). We applied a probabilistic matching algorithm using 7 variables (transplant: month, year, and type; recipient: age, sex, race, payer). We matched recipients in the USF to transplant patients in the NIS between 2016 and 2019. The Elixhauser methodology was used to identify comorbidities present on admission. We determined the associations between mortality, length of stay (LOS), total charges, and disposition with comorbidity numbers using penalized cubic splines, Kaplan-Meier, and linear and logistic regression methods.

RESULTS

From 28,484,087 NIS admissions, we identified 1,821 LT recipients. Matches were exact in 76.8% of the cohort. While the remaining cohort had a probability match of ≥0.94. Penalized splines of Elixhauser comorbidity number identified 3 knots defining 3 groups of stacked risk: low (<3), medium (3-6), and high risk (>6). Inpatient mortality increased from low to medium to high-risk categories: (1.6%, 3.9%, and 7.0%; p < 0.001), as did LOS (16, 21, 29 days, p < 0.001), total charges ($553,057, $666,791, $821,641.5; p = 0.004) and discharge to a skilled nursing facility (15%, 20%, 31%; p < 0.001).

CONCLUSIONS

Stacked risks adversely affect post-LT mortality, LOS, charges, and discharge disposition. Further study to understand the details of specific stacked risks is warranted.

Expanding Donor Options for Lung Transplant: Extended Criteria, Donation After Circulatory Death, ABO Incompatibility, and Evolution of Ex Vivo Lung Perfusion

Only using brain-dead donors with standard criteria, the existing donor shortage has never improved in lung transplantation. Currently, clinical efforts have sought the means to use cohorts of untapped donors, such as extended criteria donors, donation after circulatory death, and donors that are ABO blood group incompatible, and establish the evidence for their potential contribution to the lung transplant needs. Also, technical maturation for using those lungs may eliminate immediate concerns about the early posttransplant course, such as primary graft dysfunction or hyperacute rejection. In addition, recent clinical and preclinical advances in ex vivo lung perfusion techniques have allowed the safer use of lungs from high-risk donors and graft modification to match grafts to recipients and may improve posttransplant outcomes. This review summarizes recent trends and accomplishments and future applications for expanding the donor pool in lung transplantation.

Risk Stratification in Pulmonary Arterial Hypertension, Update and Perspectives

Risk stratification in pulmonary arterial hypertension (PAH) is crucial in assessing patient prognosis. It serves a prominent role in everyday patient care and can be determined using several validated risk assessment scores worldwide. The recently published 2022 European Society of Cardiology (ESC)/European Respiratory Society (ERS) guidelines underline the importance of risk stratification not only at baseline but also during follow-up. Achieving a low-risk status has now become the therapeutic goal, emphasising the importance of personalised therapy. The application of these guidelines is also important in determining the timing for lung transplantation referral. In this review, we summarise the most relevant prognostic factors of PAH as well as the parameters used in PAH risk scores and their evolution in the guidelines over the last decade. Finally, we describe the central role that risk stratification plays in the current guidelines not only in European countries but also in Asian countries.

The Past, Present, and Near Future of Lung Allocation in the United States

The first official donor lung allocation system in the United States was initiated by the United Network of Organ Sharing in 1990. The initial policy for lung allocation was simple with donor lungs allocated based on ABO match and the amount of time the candidates accrued on the waiting list. Donor offers were first given to candidates' donor service area. In March 2005, the implementation of the lung allocation score (LAS) was the major change in organ allocation. International adoption of the LAS-based allocation system can be seen worldwide.

The Lung Transplant Candidate, Indications, Timing, and Selection Criteria

Lung transplantation can be lifesaving for patients with advanced lung disease. Demographics are evolving with recipients now sicker but determining candidacy remains predicated on one's underlying lung disease prognosis, along with the likelihood of posttransplant success. Determining optimal timing can be challenging, and most programs favor initiating the process early and proactively to allow time for patient education, informed decision-making, and preparation. A comprehensive, multidisciplinary evaluation is used to elucidate disease progrnosis and identify risk factors for poor posttransplant outcomes. Candidacy criteria vary significantly by center, and close communication between referring and transplant providers is necessary to improve access to transplant and outcomes.

Critical Care of the Lung Transplant Patient

Lung transplantation is a therapeutic option for end-stage lung disease that improves survival and quality of life. Prelung transplant admission to the intensive care unit (ICU) for bridge to transplant with mechanical ventilation and extracorporeal membrane oxygenation (ECMO) is common. Primary graft dysfunction is an important immediate complication of lung transplantation with short- and long-term morbidity and mortality. Later transplant-related causes of respiratory failure necessitating ICU admission include acute cellular rejection, atypical infections, and chronic lung allograft dysfunction. Lung transplantation for COVID-19-related ARDS is increasingly common..

Alterations in the kallikrein-kinin system predict death after heart transplant

Heart transplantation remains the definitive treatment for end stage heart failure. Because availability is limited, risk stratification of candidates is crucial for optimizing both organ allocations and transplant outcomes. Here we utilize proteomics prior to transplant to identify new biomarkers that predict post-transplant survival in a multi-institutional cohort. Microvesicles were isolated from serum samples and underwent proteomic analysis using mass spectrometry. Monte Carlo cross-validation (MCCV) was used to predict survival after transplant incorporating select recipient pre-transplant clinical characteristics and serum microvesicle proteomic data. We identified six protein markers with prediction performance above AUROC of 0.6, including Prothrombin (F2), anti-plasmin (SERPINF2), Factor IX, carboxypeptidase 2 (CPB2), HGF activator (HGFAC) and low molecular weight kininogen (LK). No clinical characteristics demonstrated an AUROC > 0.6. Putative biological functions and pathways were assessed using gene set enrichment analysis (GSEA). Differential expression analysis identified enriched pathways prior to transplant that were associated with post-transplant survival including activation of platelets and the coagulation pathway prior to transplant. Specifically, upregulation of coagulation cascade components of the kallikrein-kinin system (KKS) and downregulation of kininogen prior to transplant were associated with survival after transplant. Further prospective studies are warranted to determine if alterations in the KKS contributes to overall post-transplant survival.

The Assessment and Outcomes of Crossmatching in Lung Transplantation in Korean Patients

BACKGROUND

In lung transplantation, human leukocyte antigen (HLA) compatibility is not included in the lung allocation score system or considered when placing donor allografts. However, HLA matching may affect the outcomes of lung transplantation. This study evaluated the current assessment status, prevalence, and effects of HLA crossmatching in lung transplantation in Korean patients using nationwide multicenter registry data.

METHODS

Two hundred and twenty patients who received lung transplantation at six tertiary hospitals in South Korea between March 2015 and December 2019 were retrospectively reviewed. Clinical data, including general demographic characteristics, primary diagnosis, and pretransplant status of the recipients and donors registered by the Korean Organ Transplant Registry, were retrospectively analyzed. Survival analysis was performed using the Kaplan-Meier method with log-rank tests.

RESULTS

Complement-dependent cytotoxic crossmatch (CDC-XM) was performed in 208 patients (94.5%) and flow cytometric crossmatch (flow-XM) was performed in 125 patients (56.8%). Among them, nine patients (4.1%) showed T cell- and/or B cell-positive crossmatches. The incidences of postoperative complications, including primary graft dysfunction, acute rejection, and chronic allograft dysfunction in positively crossmatched patients, were not significant compared with those in patients without mismatches. Moreover, Kaplan-Meier analyses showed poorer 1-year survival in patients with positive crossmatch according to CDC-XM (P < 0.001) and T lymphocyte XM (P = 0.002) than in patients without mismatches.

CONCLUSION

Positive CDC and T lymphocyte crossmatching results should be considered in the allocation of donor lungs. If unavailable, the result should be considered for postoperative management in lung transplantation.

Low body mass index as a barrier to lung transplant in cystic fibrosis

RATIONALE

Low body mass index (BMI) may influence lung transplant decisions for patients with advanced cystic fibrosis (CF) lung disease.

OBJECTIVE

Determine whether patients with advanced CF lung disease and BMI ≤17 kg/m2 are less likely to be listed for lung transplant or have a higher risk of death without listing compared to those with higher BMI.

METHODS

Using merged United Network for Organ Sharing and CF Foundation Patient Registries, we identified adults with onset of advanced lung disease (FEV1 ≤ 40% predicted) between May-2005 and December-2016. We analyzed survival using competing risks regression with cause-specific risks of listing for lung transplant and death without listing. BMI ≤ 17 kg/m2 was our predictor.

MEASUREMENTS AND MAIN RESULTS

Among 5,121 CF patients with advanced lung disease, 23% were listed for lung transplant (n = 1,201), 23% died without listing (n = 1,190), and 44% were alive without listing (n = 2,730) as of December-2016. Patients with BMI ≤ 17 kg/m2 were less likely to be listed for transplant (HR 0.69; 95% CI 0.57, 0.83) and more likely to die without listing (HR 1.63; 95% CI 1.41, 1.88). We identified important regional variations in the likelihood of referral and listing, based on BMI.

CONCLUSIONS

Patients with advanced CF lung disease and BMI ≤ 17 kg/m2 are less likely to be listed for lung transplant and have a higher risk of dying without listing, compared to those with higher BMI. Regional differences suggest access to transplant for malnourished CF patients may be limited by location.

Mesenchymal Stromal/Stem Cells and Their Products as a Therapeutic Tool to Advance Lung Transplantation

Lung transplantation (LTx) has become the gold standard treatment for end-stage respiratory failure. Recently, extended lung donor criteria have been applied to decrease the mortality rate of patients on the waiting list. Moreover, ex vivo lung perfusion (EVLP) has been used to improve the number/quality of previously unacceptable lungs. Despite the above-mentioned progress, the morbidity/mortality of LTx remains high compared to other solid organ transplants. Lungs are particularly susceptible to ischemia-reperfusion injury, which can lead to graft dysfunction. Therefore, the success of LTx is related to the quality/function of the graft, and EVLP represents an opportunity to protect/regenerate the lungs before transplantation. Increasing evidence supports the use of mesenchymal stromal/stem cells (MSCs) as a therapeutic strategy to improve EVLP. The therapeutic properties of MSC are partially mediated by secreted factors. Hence, the strategy of lung perfusion with MSCs and/or their products pave the way for a new innovative approach that further increases the potential for the use of EVLP. This article provides an overview of experimental, preclinical and clinical studies supporting the application of MSCs to improve EVLP, the ultimate goal being efficient organ reconditioning in order to expand the donor lung pool and to improve transplant outcomes.

Preoperative evaluation of pulmonary hypertension in lung transplant candidates: echocardiography versus right heart catheterization

Background

Right heart catheterization (RHC) and echocardiography are both routinely used for pulmonary artery systolic pressure (PASP) assessment in lung transplantation (LT) candidates, although this is not mandated by current guidelines. We aimed to explore the performance of echocardiographic PASP as an indicator of pulmonary hypertension in LT candidates, in order to assess the necessity of RHC.

Methods

From a retrospective registry of 393 LT candidates undergoing RHC and echocardiography during 2015–2019, patients were assessed for the presence of pulmonary hypertension (PH), defined as mean pulmonary artery pressure (mPAP) above 20 mmHg, according to two methods—echocardiography and RHC. The primary outcome was the correlation between the PASP estimated by echocardiography to that measured by RHC. Secondary outcomes were the prediction value of the echocardiographic evaluation and its accuracy.

Results

The mean value of PASP estimated by echocardiography was 49.5 ± 20.0 mmHg, compared to 42.5 ± 18.0 mmHg measured by RHC. The correlation between the two measurements was moderate (Pearson’s correlation: r = 0.609, p < 0.01). Echocardiography PASP measurements were moderately discriminative to diagnose PH, with an area under the curve (AUC) of 0.72 (95% CI 0.66–0.77). Echocardiographic overestimation of PASP of more than 10 mmHg was found in 35.0% of the patients, and underestimation was found in 11.6% of the patients.

Conclusion

In the pre-surgical evaluation of LT candidates, echocardiographic estimation of PASP had moderate correlation and limited accuracy compared to the PASP measured by RHC. We thus recommend performing routine RHC to all LT candidates, regardless of the echocardiographic estimation of PASP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02495-y.

Validation of the risk stratification score in idiopathic pulmonary fibrosis: study protocol of a prospective, multi-centre, observational, 3-year clinical trial

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is characterized by a poor prognosis, with a progressive decline in lung function and considerable variability in the disease's natural history. Besides lung transplantation (LTx), the only available treatments are anti-fibrosing drugs, which have shown to slow down the disease course. Therefore, predicting the prognosis is of pivotal importance to avoid treatment delays, which may be fatal for patients with a high risk of progression. Previous studies showed that a multi-dimensional approach is practical and effective in the development of a reliable prognostic score for IPF. In the RIsk Stratification scorE (RISE), physiological parameters, an objective measure of patient-reported dyspnea and exercise capacity are combined to capture different domains of the complex pathophysiology of IPF.

METHODS

This is an observational, multi-centre, prospective cohort study, designed to reflect common clinical practice in IPF. A development cohort and a validation cohort will be included. Patients newly diagnosed with IPF based on the ATS/ERS criteria and multi-disciplinary discussion will be included in the study. A panel of chest radiologists and lung pathologists will further assess eligibility. At the first visit (time of diagnosis), and every 4-months, MRC dyspnea score, pulmonary function tests (FEV1, FVC and DLCO), and 6-min walking distance will be recorded. Patients will be prospectively followed for 3 years. Comorbidities will be considered. The radiographic extent of fibrosis on HRCT will be recalculated at a 2-year interval. RISE, Gender-Age-Physiology, CPI and Mortality Risk Scoring System will be calculated at 4-month intervals. Longitudinal changes of each variable considered will be assessed. The primary endpoint is 3-year LTx-free survival from the time of diagnosis. Secondary endpoints include several, clinically-relevant information to ensure reproducibility of results across a wide range of disease severity and in concomitance of associated pulmonary hypertension or emphysema.

DISCUSSION

The objective of this study is to validate RISE as a simple, straightforward, inexpensive and reproducible tool to guide clinical decision making in IPF, and potentially as an endpoint for future clinical trials.

TRIAL REGISTRATION

U.S National Library of Medicine Clinicaltrials.gov, trial n. NCT02632123 "Validation of the risk stratification score in idiopathic pulmonary fibrosis". Date of registration: December 16th, 2015.

The Surplus Transplant Lung Allocation System in Italy: An Evaluation of the Allocation Process via Stochastic Modeling

Lung transplantation is a specialized procedure used to treat chronic end-stage respiratory diseases. Due to the scarcity of lung donors, constructing fair and equitable lung transplant allocation methods is an issue that has been addressed with different strategies worldwide. This work aims to describe how Italy's "national protocol for the management of surplus organs in all transplant programs" functions through an online app to allocate lung transplants. We have developed two probability models to describe the allocation process among the various transplant centers. An online app was then created. The first model considers conditional probabilities based on a protocol flowchart to compute the probability for each area and transplant center to receive each n-th organ in the period considered. The second probability model is based on the generalization of the binomial distribution to correlated binary variables, which is based on Bahadur's representation, to compute the cumulative probability for each transplant center to receive at least nth organs. Our results show that the impact of the allocation of a surplus organ depends mostly on the region where the organ was donated. The discrepancies shown by our model may be explained by a discrepancy between the northern and southern regions in relation to the number of organs donated.