Limited Survival Benefit With Expanded Kidney Donor Criteria

Medscape

07-06-2025

VIENNA — The use of expanded-criteria donors for kidney transplantation in older and high-risk recipients did not provide the same survival benefit as the use of standard donors, according to an analysis of data from more than 64,000 individuals in the European Renal Association (ERA) Registry, using target trial emulation.
'When determining who is a suitable transplant candidate, we shouldn't only focus on the patient alone, because the outcomes will also depend on donor quality,' said study presenter Rachel Hellemans, MD, PhD, a nephrologist at Antwerp University Hospital, Belgium.
'Of course, ideally, we would like to give a transplant to everyone, but shortage is a reality,' she continued.
The possibilities for older patients to receive a standard-criteria donor kidney depend on local allocation systems and waiting times. Waiting an extended period for a transplant carries the risk of clinical deterioration, Hellemans pointed out, and patients may want to 'settle for an expanded-criteria donor kidney — although, in general, these kidneys perform less well.'
'Even in the absence of a true survival difference, patients may still value this kind of transplantation to improve the quality of their remaining life years,' she said.
But clinicians need to be careful 'to interpret and communicate the results of our study' she cautioned, 'because, despite a very thorough pretransplant workup,' and 'careful decision-making as a transplant team, there remains an element of unpredictability and some very real risks, especially in the early post-transplant period.'
Exploring the Margins of Survival Benefits
The research presented here at the 62nd ERA Congress 2025 was based on an analysis of data on more than 64,000 individuals on the European Renal Association (ERA) Registry.
'Transplantation is, no doubt, the optimal treatment strategy for many of our patients with kidney failure,' said Hellemans, 'and it often leads to substantially better survival compared to continued dialysis, but its successes have also made us push the boundaries.'
She pointed out that, due to a lack of suitable donor organs, clinicians have increasingly turned to less-than-ideal donors, such as those who are older, have more comorbidities, or who have died due to circulatory disorders.
On the other hand, patients on dialysis now have improved survival, said Hellemans. Therefore, the question becomes: 'Where do the margins lie for the survival benefit with transplantation?'
'Although this may sound like a simple question,' she continued, 'it's actually a very difficult one to answer.' Ideally, a research question like this would be answered with a randomized control trial (RCT), 'which is impossible for ethical and practical reasons.'
The next best step is to turn to registry data, but this is fraught with methodological pitfalls. Hellemans said that approximately half of such studies in the field suffer from avoidable biases, likely leading to an overestimation of the true benefit of transplantation.
Moreover, the most recent comprehensive assessment of the impact of recipient age and comorbidities, and donor quality on mortality risk in older patients, was published in 2013, and Hellemans pointed out that this is a fast-evolving field, and so regular updates are required.
The researchers therefore turned to the ERA Registry, which contains data on 64,013 adults from France, Catalonia (in Spain), Denmark, Norway, and the United Kingdom who were on dialysis and wait-listed for a first deceased donor kidney transplant between 2000 and 2019.
The study investigators looked at 5-year survival with transplantation vs continued dialysis, stratified by donor type:
standard-criteria donor kidneys, or those from donors younger than 60 years of age without significant risk factors for poor kidney function; and
expanded-criteria donor kidneys, which includes all donors aged ≥ 60 years, and aged 50-59 years who had at least two of the following: a history of arterial hypertension, death from cerebrovascular accident, and/or last serum creatinine > 1.5 mg/dL.
The recipients were also stratified by age and presence of comorbidities, namely diabetes, and a history of cardiovascular disease.
To overcome the limitations of using registry data, the researchers turned to a methodological framework known as target trial emulation. Here, they treated their observational data as if it was from an RCT, in which transplantation was considered the intervention, and each transplant launched one of a series of sequential trials comparing the outcome with that seen for patients who remained on dialysis.
They then controlled for country, time on dialysis prior to wait-listing, calendar year of transplantation, patient sex, cause of kidney failure, and diabetes.
This way, Hellemans explained, they could avoid the biases that normally come with registry-based studies. Provided there is no important and measured confounding, target trial emulation can 'achieve a level of evidence that closely approximates that of a true RCT.'
Standard Criteria Donor vs Extended Criteria Donor
The results showed that, no matter the recipient's age, the 5-year adjusted survival rate was substantially better for transplant patients who received a standard-criteria donor organ than those who remained on dialysis.
However, when the researchers turned to expanded-criteria donors, they found that the survival benefit from transplant decreased with increasing recipient age — to the extent that, among those who received a donor organ after circulatory death, the advantage all but disappeared.
Among patients aged 75 years and older, 5-year survival rates for recipients who received kidneys from extended criteria donors were estimated at 57%–58%, only slightly higher than the 54% in those who remained on dialysis.
A similar pattern was seen when looking at recipients with diabetes and those with cardiovascular disease: standard-criteria donors were associated with a survival benefit with transplant over remaining on dialysis — no matter the recipient's age — while the benefit dropped off sharply with increasing age in patients receiving expanded-criteria donor organs.
A key factor was the increased early post-transplant mortality observed in older patients receiving expanded criteria kidney donations, Hellemans reported. There was a sharp rise in mortality risk compared with staying on dialysis in the first 10 months after undergoing transplant, followed by a drop-off in risk until, at 5 years, the hazard ratio for death was 1.01 (95% CI, 0.74-1.36) for the two approaches, she explained.
Limitations of the study include the heterogeneous nature of the donor population, and potential residual confounding factors due to the lack of information on the functional status of the patients, said Hellemans. In addition, the presence of diabetes and cardiovascular disease were recorded only at the time of wait-listing, thus they did not include incident cases during follow-up.
Moreover, 5-year survival as an outcome has its limitations, she pointed out, as few patients remained on dialysis beyond this timeframe.
Informed Discussions With Patients
'The breadth of data we could access via the ERA Registry showed that the survival advantage of a transplant plateaus for the very oldest or highest-risk patients who are likely to receive an expanded-criteria or circulatory-death donor kidney,' said Vianda Stel, PhD, associate professor in the Department of Medical Informatics at Amsterdam UMC, the Netherlands, and director of the ERA Registry, in a press release.
'This arms clinicians with guidance to have informed discussions with their patients. The message is not 'don't transplant older people,' ' she said, but rather 'be open about uncertainty when the numbers say benefit may be marginal.'
'We were always convinced that we can give a benefit by giving a transplant to every patient on the waiting list,' Christoph Wanner, MD, PhD, professor of medicine and head of the Division of Nephrology, University of Würzburg, Germany, told Medscape Medical News . 'And now we see that, in those aged 75 years, they will not have a benefit with the expanded donor criteria.'
He said that the 'big question' is whether the current findings will affect clinical decision-making. 'I think dialysis doctors will respond to this and maybe keep patients on dialysis for various reasons and not push them into transplant. This new data give us the justification' to make that argument.
Given that the pool of available organs cannot be expanded, Wanner believes that current waiting lists could be rationalized so that 'the organs that are available could be directed to a smaller proportion of patients, and therefore people would benefit' from lower wait times.
Daniel W. Coyne, MD, professor of medicine, Nephrology/Internal Medicine at Washington University in St. Louis, Missouri, commented on X (formerly Twitter) that the benefit with expanded-criteria donation decreases with older age 'is not what my transplant group is telling our patients in the US.'
He added: 'We need this [trial] emulation in US data.'
https://publish.twitter.com/oembed?url=https://x.com/drdanmo/status/1930572594245214209 | content
The research received no specific grant. Hellemans, Stel, Wanner, and Coyne reported no relevant financial relationships.