Discrepancy between severity of lung impairment and seniority on the lung transplantation list

Recipient selection, timing of referral, and listing for lung transplantation

Recipient selection for lung transplantation is a balance between providing access to transplantation to maximum patients, while utilizing this limited resource in the most optimal way. This review summarizes the current literature and recommendations about referral, listing, and evaluation of lung transplant candidates, with a focus on patients considered to have high risk characteristics.

Lung Transplant Mortality Is Improving in Recipients With a Lung Allocation Score in the Upper Quartile

BACKGROUND

Since the introduction of the Lung Allocation Score (LAS), the mean LAS has risen. Still, it remains uncertain whether mortality has improved in the most severely ill lung transplant recipients over this time period.

METHODS

Using the United Network for Organ Sharing database, we identified 3,548 adult lung transplant recipients from May 4, 2005, to March 31, 2014, with a match-time LAS in the upper quartile (>75th%ile). We divided this population across three eras: 1 = May 4, 2005, to December 31, 2008 (n = 1,280); 2 = January 1, 2009, to December 31, 2011 (n = 1,266); and 3 = January 1, 2012, to March 31, 2014 (n = 1,002). Cox proportional hazards models were constructed for the primary outcomes of 30-day and 1-year mortality to assess the independent impact of the era of transplantation.

RESULTS

The mean LAS at time of transplant for patients in the upper quartile in eras 1, 2, and 3 was 63, 73, and 79, respectively (p < 0.001). Later eras of transplantation benefited from a significant improvement in survival at 1 year (log-rank p = 0.001) but not at 30 days (log-rank p = 0.152). After risk adjustment, lung transplantation in more recent eras was associated with improved mortality at both 30 days (era 3 hazard ratio [HR] = 0.50, 95% confidence interval [CI] 0.32% to 0.78%, p = 0.002) and 1 year (era 2 HR = 0.77, 95% CI 0.64% to 0.94%, p = 0.008; era 3 HR = 0.54, 95% CI 0.43% to 0.68%, p < 0.001).

CONCLUSIONS

Despite a progressively rising LAS, survival is improving among recipients with the highest LAS at the time of lung transplantation. This calls into question the notion of a maximum LAS beyond which lung transplantation becomes futile, a so-called LAS ceiling.

The impact of pretransplant mechanical ventilation on short- and long-term survival after lung transplantation

Lung transplantation in mechanically ventilated (MV) patients has been associated with decreased posttransplant survival. Under the Lung Allocation Score (LAS) system, patients at greatest risk of death on the waiting list, particularly those requiring MV, are prioritized for lung allocation. We evaluated whether pretransplant MV is associated with poorer posttransplant survival in the LAS era. Using a national registry, we analyzed all adults undergoing lung transplantation in the United States from 2005 to 2010. Propensity scoring identified nonventilated matched referents for 419 subjects requiring MV at the time of transplantation. Survival was evaluated using Kaplan-Meier methods. Risk of death was estimated by hazard ratios employing time-dependent covariates. We found that pretransplant MV was associated with decreased overall survival after lung transplantation. In the first 6 months posttransplant, ventilated subjects had a twofold higher risk of death compared to nonventilated subjects. However, after 6 months posttransplant, survival did not differ by MV status. We also found that pretransplant MV was not associated with decreased survival in noncystic fibrosis obstructive lung diseases. These results suggest that under the LAS, pretransplant MV is associated with poorer short-term survival posttransplant. Notably, the increased risk of death appears to be strongest the early posttransplant period and limited to certain pretransplant diagnoses.

Does lung allocation score maximize survival benefit from lung transplantation?

OBJECTIVE

The lung allocation score was initiated in May 2005 to allocate lungs on the basis of medical urgency and posttransplant survival. However, the relationship between lung allocation score and candidate outcomes remains poorly characterized. The purpose of this study was (1) to describe outcomes by lung allocation score at the time of listing and (2) to estimate the net survival benefit of transplantation by lung allocation score.

METHODS

The United Network for Organ Sharing provided de-identified patient-level data. Analysis included lung transplant candidates aged 12 years or more and listed between May 4, 2005, and May 4, 2009 (n = 6082). Candidates were stratified according to lung allocation score at listing into 7 groups: lung allocation score less than 40, 40 to 49, 50 to 59, 60 to 69, 70 to 79, 80 to 89, and 90 or more. Outcomes of interest included the risk of death on the waiting list and likelihood of transplantation. The net survival benefit of transplantation was defined as actuarial median posttransplant graft survival minus actuarial median waiting list survival, where the outcome of interest was death on the waiting list or posttransplant; candidates were censored at the time of transplant or last follow-up.

RESULTS

In the lowest-priority strata (eg, <40 and 40-49), less than 4% of candidates died on the waiting list within 90 days of listing. The median net survival benefit was lowest in the lung allocation score less than 40 (-0.7 years) and lung allocation score 90+ group (1.95 years) and highest in the 50 to 59 (3.44 years), 60 to 69 (3.49 years), and 70 to 79 (2.81 years) groups.

CONCLUSIONS

The mid-priority groups (eg, 50-59, 60-69, 70-79) seem to achieve the greatest survival benefit from transplantation. Although low-priority candidates comprise the majority of transplant recipients, survival benefit in this group seems to be less than in other groups given the low risk of death on the waiting list. As expected, both the time to transplant and survival on the waitlist are lower in the higher-priority strata (eg, 80-89 and 90+). However, their net survival benefit was likewise relatively low as a result of their poor posttransplant survival.

High lung allocation score is associated with increased morbidity and mortality following transplantation

BACKGROUND

The lung allocation score (LAS) was initiated in May 2005 to allocate lungs based on medical urgency and posttransplant survival. The purpose of this study was to determine if there is an association between an elevated LAS at the time of transplantation and increased postoperative morbidity and mortality.

METHODS

The United Network for Organ Sharing provided de-identified patient-level data. Analysis included lung transplant recipients aged >or= 12 years who received transplants between April 5, 2006, and December 31, 2007 (n = 3,836). Recipients were stratified into three groups: LAS < 50 (n = 3,161, 83.87%), LAS 50 to 75 (n = 411, 10.9%), and LAS >or= 75 (n = 197, 5.23%), referred to as low LAS (LLAS), intermediate LAS (ILAS), and high LAS (HLAS), respectively. The primary outcome was posttransplant graft survival at 1 year. Secondary outcomes included length of stay and in-hospital complications.

RESULTS

HLAS recipients had significantly worse actuarial survival at 90 days and 1 year compared with LLAS recipients. When transplant recipients were stratified by disease etiology, a trend of decreased survival with elevated LAS was observed across all major causes of lung transplant. HLAS recipients were more likely to require dialysis or to have infections compared with LLAS recipients (P < .001). In addition, length of stay was higher in the HLAS group when compared with the LLAS group (P < .001).

CONCLUSIONS

HLAS is associated with decreased survival and increased complications during the transplant hospitalization. Whereas the LAS has improved organ allocation through decreased waiting list deaths and waiting list times, lower survival and higher morbidity among HLAS recipients suggests that continued review of LAS scoring is needed to ensure optimal long-term transplant survival.

Waiting list mortality among children listed for heart transplantation in the United States

BACKGROUND

Children listed for heart transplantation face the highest waiting list mortality in solid-organ transplantation medicine. We examined waiting list mortality since the pediatric heart allocation system was revised in 1999 to determine whether the revised allocation system is prioritizing patients optimally and to identify specific high-risk populations that may benefit from emerging pediatric cardiac assist devices.

METHODS AND RESULTS

We conducted a multicenter cohort study using the US Scientific Registry of Transplant Recipients. All children <18 years of age who were listed for a heart transplant between 1999 and 2006 were included. Among 3098 children, the median age was 2 years (interquartile range 0.3 to 12 years), and median weight was 12.3 kg (interquartile range 5 to 38 kg); 1294 (42%) were nonwhite; and 1874 (60%) were listed as status 1A (of whom 30% were ventilated and 18% were on extracorporeal membrane oxygenation). Overall, 533 (17%) died, 1943 (63%) received transplants, and 252 (8%) recovered; 370 (12%) remained listed. Multivariate predictors of waiting list mortality include extracorporeal membrane oxygenation support (hazard ratio [HR] 3.1, 95% confidence interval [CI] 2.4 to 3.9), ventilator support (HR 1.9, 95% CI 1.6 to 2.4), listing status 1A (HR 2.2, 95% CI 1.7 to 2.7), congenital heart disease (HR 2.2, 95% CI 1.8 to 2.6), dialysis support (HR 1.9, 95% CI 1.2 to 3.0), and nonwhite race/ethnicity (HR 1.7, 95% CI 1.4 to 2.0).

CONCLUSIONS

US waiting list mortality for pediatric heart transplantation remains unacceptably high in the current era. Specific high-risk subgroups can be identified that may benefit from emerging pediatric cardiac assist technologies. The current pediatric heart-allocation system captures medical urgency poorly. Further research is needed to define the optimal organ-allocation system for pediatric heart transplantation.

Thoracic organ transplantation in the United States, 1995-2004

This article reviews trends in thoracic organ transplantation based on OPTN/SRTR data from 1995 to 2004. The number of active waiting list patients for heart transplants continues to decline, primarily because there are fewer patients with coronary artery disease listed for transplantation. Waiting times for heart transplantation have decreased, and waiting list deaths also have declined, from 259 per 1000 patient-years at risk in 1995 to 156 in 2004. Fewer heart transplants were performed in 2004 than in 1995, but adjusted patient survival increased to 88% at 1 year and 73% at 5 years. Emphysema, idiopathic pulmonary fibrosis and cystic fibrosis were the most common indications among lung transplant recipients in 2004. Waiting time for lung transplantation decreased between 1999 and 2004. Waiting list mortality decreased to 134 per 1000 patient-years at risk in 2004. One-year survival following transplantation has improved significantly in the past decade. The number of combined heart-lung transplants performed in the United States remains low, with only 39 performed in 2004. Overall unadjusted survival, at 58% at 1 year and 40% at 5 years, is lower among heart-lung recipients than among either heart or lung recipients alone.