Fair Play for Transplants
STANFORD GRADUATE SCHOOL OF BUSINESS—Kidney transplant surgery is a victim of its own success. The demand for kidneys has created a dramatic shortage, raising the difficult problem of organ allocation. It's an issue that has long troubled physicians and is now also being tackled by GSB statistical theorist Stefanos Zenios.
The first kidney transplant was performed in 1954, but long-term survival remained improbable until a breakthrough in the development of immunosuppressive drugs in 1978. Suddenly, success rates skyrocketed. Organ survival after one year is now 79 percent or better, which has turned transplantation into the treatment of choice for kidney failure. It is not only the cheapest treatment, but it improves patients' quality of life the most. About 40,000 transplants are now performed every year, about a quarter of them in the United States, but it is not uncommon for patients to wait 18 months or more before a suitable donor is found.
Zenios, an assistant professor of operations, information, and technology at the Business School, has created a statistical model to analyze several kidney allocation policies. It considers such wrenching trade-offs as cost versus medical benefit, cost versus mortality, cost versus transplant survival, cost versus equity, and equity versus mortality. "The model is the first step to building a better allocation system, and the results will provide insights about the effect of allocation policies on health, expense, and fairness," says Zenios. Using his model to test different policies, new decisions on allocation will be made by the United Network of Organ Sharing, a nonprofit organization that monitors organ distribution.
Under the current setup, a central allocation organization ranks patients according to how well their tissue matches that of an available kidney and how long they have been on the waiting list. This means that healthy patients with uncommon tissue types may wait an extremely long time, while patients with common tissue types but shorter life expectancy -- due to either poor health or old age -- receive all available kidneys. By the time the robust patient's turn comes up, his health may be compromised. If some of these healthy patients were given an opportunity to match at an earlier point in time, the outcome could be better.
Changing the allocation formulas may improve the system, but it cannot end the shortage of organs. Financial incentives, such as paying donors' relatives for funeral expenses, are increasingly discussed as a method for expanding the organ supply, says Zenios, who is also examining the cost-effectiveness of such incentives. This research is of special relevance to Medicare because the high cost of caring for kidney patients is a much criticized portion of the Medicare program, which currently pays for 90 percent of the kidney transplants in the United States.
Although the model developed by Zenios targets kidney distribution, it can be adapted to review heart, liver, pancreas, and heart-lung transplantation, as well as to study the efficacy of using promising, but still imperfect, vaccines for HIV, the virus that causes AIDS.
Dynamic Allocation of Kidneys to Candidates on the Transplant Waiting List, by Stefanos A. Zenios and Lawrence M. Wein, GSB Research Paper #1429, January 1997