Xenotransplantation: risks, clinical potential, and future prospects.

The reemergence of xenotransplantation as a therapeutic option for the hundreds of thousands of people dying each year of heart, kidney, lung, and liver failure has raised ethical, social, and scientific questions. End-stage organ failure is one of the most important public health problems facing Americans today. Heart failure, for example, kills four times as many people as does HIV infection and three times as many people as does breast cancer; it is a disease with an increasing incidence, and the cost of taking care of affected patients is 8 to 35 billion dollars each year. The single most effective therapy for it is transplantation. Preventive therapies have had little impact on diseases due to end-stage organ failure and are unlikely to have an impact at least in the next decade. In the meantime, demand for organs, which far outstrips the supply, continues to grow. It has been estimated that approximately 45,000 Americans under age 65 could benefit each year from heart transplantation, yet only 2,000 human hearts are available annually. Patients are more likely to die waiting for a human donor heart than in the first 2 years after transplantation.