Differential Impact of Extended-Criteria Donor Use According to Recipient Status in Lung Transplantation: A Nationwide Cohort Study

Abstract

Background

The use of extended-criteria donors (ECDs) in lung transplantation remains high in Korea; however, their impact on survival outcomes is not fully understood.

Methods

We retrospectively analyzed 1,251 adult lung transplant recipients registered with the Korea Network for Organ Sharing (2010–2023). ECDs were defined as donors aged ≥ 55 years with a smoking history ≥ 20 pack-years or a PaO₂/FiO₂ ratio ≤ 300. Survival outcomes were assessed using Kaplan-Meier analysis and multivariable Cox regression, with subgroup comparisons by urgency (status 0 vs. status 1–4) and age (< 65 vs. ≥ 65 years).

Results

Of the 1,251 recipients, 33.7% received ECD lungs. In the multivariable analysis, recipient age, urgency status 0, and ECD use were independently associated with increased one-year mortality. In subgroup analyses, ECD use was consistently associated with higher mortality in status 1–4 recipients (P < 0.001), whereas in status 0 recipients it showed only a trend toward decreased survival (P = 0.056). Among elderly recipients, ECD use significantly increased mortality in status 1–4 but showed only a trend toward decreased survival in status 0 (P = 0.071). In contrast, among younger recipients, ECD use increased mortality in status 1–4 but had no significant effect in status 0.

Conclusion

ECD use was consistently associated with higher one-year mortality in recipients with urgency status 1–4, irrespective of age. In contrast, among status 0 recipients, the effect differed by age. These findings highlight the importance of incorporating both recipient urgency and age into donor lung selection.

Graphical Abstract

INTRODUCTION

A persistent imbalance between lung supply and demand remains a major challenge in organ transplantation. In Korea, the shortage of lung donors is higher than that in other countries, leading to high waiting-list mortality.1,2 This scarcity is exacerbated by suboptimal donor management, resulting in a significant proportion of donor lungs being deemed unsuitable for transplantation.2,3 To mitigate this issue, the use of extended-criteria donors (ECDs) has increased.

The traditional donor selection criteria include age, pulmonary function, smoking history, chest radiography findings, and bronchoscopy results.4 However, the number of donor lungs that meet these criteria is insufficient to meet the growing demand. Consequently, to expand the donor pool, lungs from donors meeting only minimal criteria for age, smoking history, and lung function have been increasingly used. According to the United States Organ Procurement and Transplantation Network (OPTN)/United Network for Organ Sharing (UNOS) database, 56% of transplanted donor lungs do not meet at least one ideal donor criterion.4 Despite this approach, the use of ECDs remains controversial.

Internationally, there is no consensus on the impact of ECDs on post-transplant outcomes. A retrospective study of 123 lung transplant recipients in Toronto reported acceptable early mortality rates in ECD lung recipients.5 In contrast, a single-center study by Moreno et al.6 involving 365 lung transplants concluded that recipient characteristics rather than donor status were the primary determinants of survival. Recent studies have suggested that ECD outcomes may vary depending on recipient severity.7 However, inconsistent ECD definitions across studies have contributed to the ongoing debate regarding the impact of ECD on survival.

In Korea, reliance on ECD transplantation remains high because of high waiting-list mortality, advancements in medical care, and persistent donor shortages. However, its effect on lung transplant outcomes has not been thoroughly evaluated. Given the necessity of ECD in the face of severe waiting list congestion, we aimed to analyze the effect of ECD lung transplantation and matching donor quality with recipient urgency on post-transplant survival in Korea.

METHODS

Study design and data collection

We retrospectively reviewed and analyzed data from the Korean Network for Organ Sharing (KONOS) database. The dataset was provided to our research team through a government-funded KONOS policy research project conducted in 2024 (“Study on ways to improve the efficiency of lung transplantation from brain-dead organ donors”). In accordance with the data use agreement, access was granted exclusively to authorized investigators and limited to a predefined timeframe. This study included all lung-only transplant registrations conducted between January 2010 and October 2023 (Supplementary Fig. 1). The survival status and date of death were tracked for all patients until October 2024.

The collected data included donor and recipient characteristics, including age, sex, body mass index, date of registration, primary diagnosis, ABO blood type, urgency status at registration, date of transplantation, urgency status at transplantation, and post-transplant survival duration. The primary diagnoses of lung transplant recipients were categorized into ten disease groups: chronic obstructive pulmonary disease, bronchiectasis, cystic fibrosis, lymphangioleiomyomatosis, primary pulmonary hypertension, Eisenmenger syndrome, idiopathic pulmonary fibrosis (IPF), asbestos, bronchiolitis obliterans syndrome following transplantation, and other lung diseases. Patients were classified as elderly if they were aged ≥ 65 years at registration, and as non-elderly if they were aged < 65 years.

Classification of urgency status

Patients were stratified into five urgency categories (status 0–4) based on predefined medical criteria.8 Status 0 was defined as hospitalization with mechanical ventilation (MV) and/or extracorporeal membrane oxygenation (ECMO) due to respiratory failure. The detailed criteria for status 1–4 are summarized in Supplementary Table 1.

Donor classification

Donors were classified as ECDs if they met at least one of the following conditions9: age ≥ 55 years, PaO₂/FiO₂ ratio ≤ 300 mmHg, and smoking history ≥ 20 pack-years. Donors who did not meet these criteria were classified as standard donors (SCDs).

Statistical analysis

Categorical variables were presented as frequencies and percentages, whereas continuous variables were expressed as means with standard deviations or medians with interquartile ranges, depending on the data distribution. Comparisons between groups were performed using Student’s t-test or Mann-Whitney U test for continuous variables and χ² or Fisher’s exact test for categorical variables. A Cox proportional hazards regression model was used to identify the factors associated with one-year post-transplant mortality. Variables with P < 0.20 in univariate analysis were included in a stepwise backward multivariate Cox regression model. Survival analysis was conducted using the Kaplan-Meier method, and differences between groups were assessed using the log-rank test. All the statistical analyses were performed using MedCalc (version 11.3.6.0; MedCalc Software, Mariakerke, Belgium) and SPSS (version 27; IBM Corp., Armonk, NY, USA). Statistical significance was set at P < 0.05.

Ethics statement

This study was approved by the Institutional Review Board of the Pusan National University Yangsan Hospital (approval No. 05-2024-057). The requirement for informed consent was waived due to the retrospective nature of the study and the use of anonymized data.

RESULTS

Characteristics of ECDs and SCDs

During the study period, 1,251 adult patients underwent lung transplantation. Of these, 33.7% received lungs from ECDs and 66.3% received lungs from SCDs. The baseline characteristics of the recipients, stratified by donor type, are presented in Table 1. Recipients in the SCD group were younger than those in the ECD group (mean age: 53.5 vs. 55.4 years, P = 0.004). Additionally, there was a significant difference in the ABO blood type distribution between the two groups.

Table 1. Characteristics of extended and SCDs.

Variables		SCD (n = 829)	ECD (n = 422)	P value
Age, yr		53.5 ± 11.9	55.4 ± 10.9	0.004
Male		524 (63.2)	277 (65.6)	0.397
Height		165.1 ± 8.3	164.5 ± 10.9	0.274
BMI, kg/m2		21.6 ± 4.1	22.0 ± 4.2	0.107
ABO type				0.027
	A	289 (34.9)	161 (38.2)
	B	245 (29.6)	99 (23.5)
	O	169 (20.4)	108 (25.6)
	AB	126 (15.2)	54 (12.8)
Diagnosis				0.644
	Primary pulmonary hypertension	16 (1.9)	14 (3.3)
	IPF	390 (47.0)	197 (46.7)
	Emphysema	13 (1.6)	3 (0.7)
	Cystic fibrosis	4 (0.5)	1 (0.2)
	Bronchiectasis	38 (4.6)	16 (3.8)
	Asbestosis	1 (0.1)	2 (0.5)
	BO after transplant	43 (5.2)	24 (5.7)
	Eisenmenger	5 (0.6)	2 (0.5)
	Lymphangioleiomyomatosis	12 (1.4)	4 (0.9)
	Other	307 (37.0)	159 (37.7)
Status at transplantation				0.621
	Status 0	489 (59.0)	245 (58.1)
	Status 1	296 (35.7)	159 (37.7)
	Status 2–4	44 (5.3)	18 (4.3)

Data presented as the mean ± standard deviation or number (%).

SCD = standard criteria donor, ECD = extended-criteria donor, BMI = body mass index, IPF = idiopathic pulmonary fibrosis, BO = bronchiolitis obliterans.

Risk of ECD use for one-year mortality

Univariate and multivariate analyses were conducted to identify factors associated with one-year post-transplant mortality (Table 2). In multivariate Cox regression analysis, recipient age, ECD use, and urgency status at transplantation were independently associated with one-year mortality. Notably, ECD use was significantly associated with worse posttransplant outcomes than SCD use (χ² = 14.65, P < 0.001; Fig. 1).

Table 2. Cox regression for post-transplant one-year mortality.

Variables	Univariate		Multivariate
	HR (95% CI)	P value	HR (95% CI)	P value
Age	1.02 (1.01–1.04)	< 0.001	1.02 (1.01–1.03)	< 0.001
ECD	1.49 (1.21–1.83)	< 0.001	1.44 (1.17–1.77)	0.001
Status 0 at transplantation	1.60 (1.29–1.99)	< 0.001	1.62 (1.30–2.01)	< 0.001
BMI, kg/m2	1.02 (0.99–1.04)	0.141	-	-
Male	0.94 (0.76–1.16)	0.570	-	-

HR = hazard ratio, CI = confidence interval, ECD = extended-criteria donor, BMI = body mass index.

Fig. 1. Kaplan-Meier transplant survival according to donor quality. ECD use was significantly associated with worse post-transplant outcomes than SCD use (χ² = 14.65, P < 0.001).

SCD = standard criteria donor, ECD = extended-criteria donor.

Impact of matching donor quality on recipient urgency

Direct comparisons between ECDs and SCDs were performed within each urgency subgroup to further evaluate the differential impact of ECD use on recipient urgency (Supplementary Table 2). Survival outcomes across the four groups were analyzed using Kaplan-Meier curves (χ² = 34.32, P < 0.001; Fig. 2). Within these subgroups, compared with SCD use in status 1–4, higher mortality was observed with ECD use in status 1–4 (hazard ratio [HR], 1.99), SCD use in status 0 (HR, 1.93), and ECD use in status 0 (HR, 2.48).

Fig. 2. Kaplan-Meier transplant survival according to donor quality and recipient severity. Survival outcomes across the four groups were analyzed using Kaplan-Meier curves (χ² = 34.32, P < 0.001). Within these subgroups, higher mortality was observed with ECD use in status 1–4 (HR, 1.99), SCD use in status 0 (HR, 1.93), and ECD use in status 0 (HR, 2.48) than with SCD use in status 1–4.

SCD = standard criteria donor, ECD = extended-criteria donor, HR = hazard ratio, CI = confidence interval.

Subgroup analysis by pre-transplant urgency and age

In urgency status 1–4, ECD use was significantly associated with higher mortality compared with SCD use (χ² = 15.55, P < 0.001; Fig. 3). In contrast, among recipients with status 0, ECD use tended to be associated with worse post-transplant outcomes than SCD use, although this difference did not reach statistical significance (χ² = 3.64, P = 0.056; Fig. 4).

Fig. 3. Kaplan-Meier transplant survival according to donor quality in status 1–4. In urgency status 1–4, ECD use was significantly associated with higher mortality risk than SCD use (χ² = 15.55, P < 0.001).

SCD = standard criteria donor, ECD = extended-criteria donor.

Fig. 4. Kaplan-Meier transplant survival according to donor quality in status 0. In status 0, ECD use tended to show worse post-transplant outcomes compared with SCD use, but the difference did not reach statistical significance (χ² = 3.64, P = 0.056).

SCD = standard criteria donor, ECD = extended-criteria donor.

In elderly recipients (≥ 65 years), baseline characteristics were comparable between the ECD and SCD groups across urgency categories (Supplementary Table 3). Within this population, ECD use was significantly associated with worse post-transplant outcomes overall (χ² = 11.99, P = 0.001; Fig. 5). Specifically, in status 1–4 elderly recipients, ECD use was significantly associated with higher mortality (χ² = 10.46, P = 0.001; Supplementary Fig. 2), whereas in status 0 it showed only a trend toward decreased survival (χ² = 3.26, P = 0.071; Supplementary Fig. 3).

Fig. 5. Kaplan-Meier transplant survival according to donor quality in elderly patients. ECD use was significantly associated with worse post-transplant outcomes compared with SCD use (χ² = 11.99, P = 0.001).

SCD = standard criteria donor, ECD = extended-criteria donor.

Among younger recipients (< 65 years), ECD use was likewise associated with worse post-transplant outcomes compared with SCD use (χ² = 5.76, P = 0.016; Supplementary Fig. 4). In status 1–4 younger recipients, ECD use remained significantly associated with higher mortality risk (χ² = 6.01, P = 0.014; Supplementary Fig. 5), while in status 0 it had no significant effect on survival (χ² = 1.47, P = 0.226).

DISCUSSION

This study evaluated the impact of ECD lungs on post-transplant survival, with an emphasis on recipient urgency and age. We found that ECD was associated with worse overall outcomes. The combination of ECD lungs and preoperative high urgency status resulted in the lowest survival rates among all donor-recipient combinations (Fig. 2). ECD use significantly affected post-transplant outcomes among status 1–4 irrespective of the age group. However, in highly urgent situations, the impact of ECD use on post-transplant outcomes differed according to recipient age. This suggests that both recipient age and clinical condition should be considered in combination when selecting donor lungs.

The definition of an “ideal” lung donor has remained largely unchanged since the 1980s, with fewer than 30% of donor lungs currently meeting the strict criteria.2,10,11,12,13,14 As a result, ECD lungs, which do not meet the standard criteria, are being increasingly utilized. Although transplant centers are cautious about their use due to concerns regarding graft quality and long-term outcomes, ECDs have become an essential option for reducing waitlist mortality. A recent German study reported that only 19% of lung transplants used ideal donor lungs, whereas more than 30% involved ECDs.13 In Korea, reliance on ECDs has been even greater: approximately 34% of transplanted lungs are from ECDs, with the proportion declining modestly from 40% in 2014 to 37.8% in 2023 (Supplementary Fig. 6). Despite this, the effect of ECD use on post-transplant survival in Korea has not yet been comprehensively evaluated. Given the persistent donor shortage, optimizing donor-recipient matching is critical for maximizing the utility of scarce grafts and improving outcomes.

Korea continues to face severe donor shortages. For cultural, procedural, and legal reasons, many potential donors are missed, and donor lung quality is often suboptimal due to insufficient donor management practices.3,15 Additionally, many Korean transplant candidates have IPF with rapid progression, leading to the frequent use of bridging therapies, such as ECMO and MV.8,16 Consequently, nearly 30% of the adult candidates die or are delisted while awaiting transplantation.1 The increased use of ECD lungs over the past decade is a pragmatic response to this critical situation. Although an earlier single-center Korean study reported no significant differences in outcomes between ECD and SCD lungs, its generalizability is limited.9 Since 2019, lung transplantation in Korea has matured with increasing procedural volume and institutional expertise.17,18 To determine whether this evolution has influenced outcomes, we performed a subgroup analysis comparing the two eras (2010–2018 vs. 2019–2023). As shown in Supplementary Figs. 7 and 8, overall survival improved in the more recent era; however, ECD use remained consistently associated with inferior outcomes across both periods. This suggests that the detrimental effect of ECDs persists despite institutional advances and must be carefully considered in donor–recipient matching.

Several studies have examined the effect of non-ideal donor lungs on short-term survival. Christie et al.14 analyzed all lung transplants in the United States from 2005 to 2018 and found no significant differences in survival at 30, 90, or 365 days. Halpern et al.19 reported similar findings, noting no adverse short-term outcomes even in centers that aggressively utilized non-ideal lungs. However, our results are consistent with the OPTN and UNOS data, indicating that ECD lungs may be associated with worse outcomes.7 Importantly, in a subgroup analysis of critically ill patients, the effect of ECD use varied by age. Together, these findings support the growing consensus that individualized donor–recipient matching is essential. In particular, our study highlights that ECD use in status 1–4 recipients should be approached with caution given the high risk of poor survival. Although earlier studies did not identify age as a strong prognostic factor, our results indicate that it plays a critical role.20 Advanced age is often associated with poorer outcomes due to comorbidities and increased physiological vulnerability.21,22,23 Notably, in our cohort, 55.7% of elderly recipients underwent transplantation while on ECMO or MV, a much higher proportion than that reported in other countries. This may partially explain the worse age-related outcomes observed in the present study.

One often overlooked aspect of ECD is patient autonomy. Candidates should be thoroughly informed of the risks and potential benefits of accepting ECD lungs. Based on donor quality and pretransplant urgency, elderly recipients undergoing ECD transplantation at status 0 demonstrated a 1-year survival rate of < 50%, indicating that such grafts should generally be avoided in this population (Supplementary Fig. 2). In contrast, for younger recipients, accepting an ECD lung while in status 0 may remain a viable option, provided the patient has not yet reached a clinically futile stage. It is also important to recognize that even lungs with SCD may result in suboptimal outcomes if transplantation is performed under high-urgency conditions. Therefore, decision-making should account not only for donor quality but also for recipient age, urgency, and timing, with patients, caregivers, and physicians actively participating in the process.

This study has several limitations. As a retrospective analysis using the KONOS database, this study lacks detailed donor information (e.g., smoking history and imaging) and granular recipient data. To improve donor–recipient matching strategies, future research should incorporate richer clinical data and prospective validation. Despite these limitations, our findings highlight the importance of moving beyond binary classification of donor lungs. The results suggest that a nuanced approach considering the dynamic interplay between donor quality and recipient conditions is essential. This is especially relevant in Korea, where donor shortages are severe and many transplants are performed under high-urgency conditions. Tailored donor–recipient matching strategies, grounded in data and individual risk profiles, are critical for optimizing survival and ensuring the efficient use of scarce donor lungs. As lung transplantation evolves, aligning clinical decision-making with national data will be the key to refining allocation systems, personalizing treatment, and ultimately matching the right lung to the right patient at the right time.

SUPPLEMENTARY MATERIALS

Supplementary Table 1

Criteria for urgency status 0–4 in lung transplantation

Supplementary Table 2

Comparison of baseline characteristics for recipients with status 0 and statuses 1–4 at transplantation by donor type

Supplementary Table 3

Comparison of baseline characteristics for elderly recipients by donor type

Supplementary Fig. 1

Patient flow.

Supplementary Fig. 2

Kaplan–Meier survival curves for elderly recipients (≥ 65 years) with urgency statuses 1–4, comparing extended-criteria donor and standard-criteria donor.

Supplementary Fig. 3

Kaplan–Meier survival curves for elderly recipients (≥ 65 years) with urgency status 0, stratified by donor type (ECD vs. SCD).

Supplementary Fig. 4

Kaplan–Meier survival curves for non-elderly recipients (< 65 years), stratified by donor type (ECD vs. SCD).

Supplementary Fig. 5

Kaplan–Meier survival curves for non-elderly recipients (< 65 years) with urgency statuses 1–4, comparing extended-criteria donor and standard-criteria donor.

Supplementary Fig. 6

Annual proportion of extended-criteria donors used in lung transplantation in Korea from 2010 to 2023.

Supplementary Fig. 7

Kaplan–Meier survival curves according to donor type in lung transplantation performed from 2010 to 2018.

Supplementary Fig. 8

Kaplan–Meier survival curves according to donor type in lung transplantation performed from 2019 to 2023.