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Groundbreaking achievement
With the support of a donor exchange system developed by 艾可直播 College economists Tayfun S枚nmez and Utku 脺nver, Turkey鈥檚 陌n枚n眉 University recently performed the largest liver transplant exchange in history.
The so-called eight-way liver exchange involved surgeons at 陌n枚n眉鈥檚 medical school performing 16 operations simultaneously, involving eight recipients and eight donors. The procedures were performed on June 12 and took 22 hours.
The program in Turkey 鈥渉as established itself as the global leader in both the scale and complexity of liver exchange,鈥� said S枚nmez. 鈥淢ore importantly, it has demonstrated how the careful economic design of an exchange system can dramatically increase access to transplantation.
BC economists Tayfun S枚nmez (right) and Utku 脺nver.
鈥淥ur objective is not to set records," he added. "It is to maximize the benefit to patients and to society by facilitating as many high-quality transplants as possible, while using the smallest and least logistically demanding exchanges needed to achieve that objective.鈥�
脺nver recalled the excitement of learning that a new group of patients had received treatment.
鈥淣aturally, messages went back and forth between the medical team and us throughout that day as we waited for news鈥攖hat is routine on surgery days,鈥� said 脺nver. 鈥淎fter 22 hours, word came that all of the operations had succeeded. What made it even more striking for Tayfun and me is that we were both traveling at the time, working in time zones far from our usual ones, when we identified the eight-way cycle and the operations were carried out. Professor [Sezai] Y谋lmaz and his team are extraordinarily experienced鈥攖hey have performed more than 4,000 liver transplants over the past decade and a half鈥攕o however anxious or complicated any given day may be, there is always a reassuring confidence in the back of our minds.鈥�
S枚nmez and 脺nver, both natives of Turkey, are recognized world-leading experts and developers of matching mechanisms, particularly in the area of kidney and liver exchange and transplantation. Their work in 鈥渕atching markets鈥� has also focused on how to improve K-12 school choice algorithms and the assignment of cadets to military specialties in the U.S. Army.
With the historic multi-party exchange, the Banu Bedestenci S枚nmez Liver Paired Exchange Program鈥搉amed in honor of S枚nmez鈥檚 late wife鈥揾as performed 414 liver exchange transplants since the program鈥檚 inception in 2022, surpassing within four years the worldwide historical total of fewer than 250 that have taken place in the prior two decades. In 2025 alone, the system facilitated 155 liver transplants, accounting for nearly half of liver transplants done at the Institute.
The program 鈥渉as established itself as the global leader in both the scale and complexity of liver exchange. More importantly, it has demonstrated how the careful economic design of an exchange system can dramatically increase access to transplantation.鈥�
The program鈥檚 ability to conduct multi-way exchanges has revolutionized liver transplantation. These complex procedures overcome the challenges of matching donors and recipients, providing life-saving transplants to patients who would otherwise not receive them. Among other factors, the program developed by S枚nmez and 脺nver helps to maintain transplant opportunities for multiple patients by ensuring blood-type compatibility and compatibility in the size of the liver grafts.
鈥淭he 陌n枚n眉 Institute's ability to field large surgical teams is what makes exchanges bigger than two-way possible鈥攂ut we use that capacity only when it is needed. In 2025, exchange accounted for nearly half of all liver transplants at the Institute; at the leading Asian centers, it has traditionally contributed only a few percent,鈥� said 脺nver.
鈥淭he program has set new standards by performing the world鈥檚 first four-way liver exchange in June 2022,聽 the first five-way liver exchange in October 2023, the first six-way liver exchange in January 2024, and the first seven-way liver exchange in July 2024,鈥� said S枚nmez. Some of these groundbreaking procedures were documented by the economists in two papers in the American Journal of Transplantation, the premier scholarly outlet for the field. In recognition of their contributions, 陌n枚n眉 University honored 脺nver and S枚nmez with honorary doctorates in 2024.
鈥淢ulti-way exchanges overcome the difficulty in matching by serving more patients鈥攕ome of them in critical condition, who would not otherwise receive immediate transplants鈥攁nd by providing others with better transplants than they would get in smaller exchanges or directly from their own compatible donors,鈥� said 脺nver.
鈥淗owever, approximately 60-70 percent of the outcomes achieved by our system could have been achieved using two-way exchanges alone. This shows that the potential benefits of liver exchange are much broader than the ability to conduct exceptionally large exchanges. The eight-way exchange is a major medical and logistical accomplishment, but it represents only one dimension of the system鈥檚 success,鈥� added S枚nmez.
鈥淢ulti-way exchanges overcome the difficulty in matching by serving more patients鈥攕ome of them in critical condition, who would not otherwise receive immediate transplants鈥攁nd by providing others with better transplants than they would get in smaller exchanges or directly from their own compatible donors.鈥�
The economists continue to upgrade the mechanisms of their matching process.
鈥淎 great deal has changed, though the core matching algorithm has stayed the same鈥攁nd what Tayfun and I contribute goes well beyond providing software,鈥� said 脺nver. 鈥淢ost of the changes aim to improve recruitment of patient鈥揹onor pairs, so that the pool is structured to produce the best possible results, and we have steadily enriched the software we use to take advantage of the matches the pool makes possible.
鈥淭he Institute team can now conduct up to ten-way exchanges, simultaneously utilizing 20 surgery rooms and more than 160 medical personnel,鈥� said 脺nver, up from seven-way exchanges a few years ago. 鈥淭his capacity is instrumental in conducting larger exchanges. Similar capabilities do not exist in any other single center.鈥�
The economists are active partners with the medical team when the transplant procedures are in the planning and assignment stage.
鈥淏oth Tayfun and I take part in running the system day to day, and we propose the best available set of matches to the physicians,鈥� said 脺nver. 鈥淲e give them a broad menu of options, and the surgeons make the final choice.鈥�
Currently, in comparison with the 414 transplants performed at the Turkish medical center, only one other center in the world has passed 100 liver exchange transplants. The U.S. total last year was about 30 transplants from such exchanges.
Medical centers in India and Pakistan are in discussions with S枚nmez and 脺nver to put their program in place in transplant centers located in those countries.