New Strategies to Boost Renal Transplants

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New Strategies to Boost Renal Transplants

John Schieszer
February 23 2009

MARCO ISLAND, Fla.—Domino paired donation (DPD) and never-ending altruistic donor (NEAD) chains are part of a new spectrum of options for patients with end-stage renal disease (ESRD) who need renal transplants but have incompatible donors.

New data presented here at the American Society of Transplant Surgeons 9th Annual State of the Art Winter Symposium suggest that both DPD and NEAD chains may significantly expand the benefits of kidney paired-donation (KPD) to a larger number of incompatible donors. In addition, both modalities could bring desired blood-type donors into paired donation and relax reciprocal requirements that often make it difficult for some incompatible pairs to match.

“Now we have some new options for these patients,” said Robert Montgomery, MD, PhD, director of the comprehensive transplant center at Johns Hopkins Medical Institutions in Baltimore. “The results from these strategies are extremely good. The data show that patients who are not offered these options have a survival that is far less than patients who are.”

KPD involves matching a potential kidney recipient and his or her incompatible donor to another incompatible pair. This allows the donor of each pair to give his or her kidney to the recipient of the other pair. Many incompatible pairs often remain unmatched through traditional KPD, however, so researchers have been investigating DPD and NEAD chains as possible avenues for expanding KPD through the contributions of nondirected donors.

Investigators at the United States Naval Academy in Annapolis, Md., and Johns Hopkins compared the net number of transplants for three scenarios: DPD, NEAD chains, or nondirected donors giving a kidney to someone on a waitlist to receive a deceased donor kidney. When using the DPD approach, a nondirected donor gives a kidney to the recipient of an incompatible pair. This begins a string of simultaneous transplants that ends with a living donor giving to a recipient on the deceased donor waitlist. In the recently introduced NEAD chains concept, the last donor of the string of transplants initiated by a nondirected donor is reserved to donate at a later time.

Dr. Montgomery's group simulated pools of incompatible donor/recipient pairs and nondirected donors over 24 months, using a clinically detailed model previously described (Am J Transplant. 2005;5:1914-1921). The investigators used an optimization algorithm that picked the best set of two-way and three-way matches for each fixed pool of recipients and donors. For the NEAD chains, they tested various heuristics to ensure that the bridge donor would be likely to match in a future pool.

DPD could allow each nondirected donor to facilitate to an average of 1.9 transplants. NEAD chains could allow for an average of 1.8 transplants for each nondirected donor. Each modality could yield considerably more than the one transplant achieved when a nondirected donor makes a kidney available directly to the waitlist of patients waiting for a deceased donor kidney. NEAD chains may be a less attractive option than DPD because they shift matches away from traditional KPD to more complex chain arrangements and away from waitlist recipients, without increasing the number of patients transplanted.

The mode for match arrangements for each NEAD chain over 24 months is one. That means bridge donors would experience long waits before suitable recipients were found. The researchers also found that heuristic strategies of penalizing or disallowing hard-to-match AB-type bridge donors would not increase the utility of NEAD chains.

NEAD chains require a donor to pledge to donate at a future date. NEAD chains also sequester all benefit from nondirected donors to the population of people who have a living donor available, and do not increase the number of recipients transplanted compared with DPD.

“If tomorrow we were able to get all these patients into these programs where they would have access to these types of kidney paired donations, we would probably do an additional 1,500 to 2,000 live donor transplants a year,” Dr. Montgomery said. “That is about a 20% increase. It is dramatic and [would be] the biggest increase in recent decades.”

http://www.renalandurologynews.com/New-Strategies-to-Boost-Renal-Transplants/article/127709/