First Major Kidney Transplant Study Shows Increased Organ Survival Rates

The survival rates for kidney transplants from both living donors and cadavers has improved significantly over time, according to a study by Medical College of Wisconsin researchers. The study, published in the March 2, 2000 issue of the New England Journal of Medicine, is the first to show that long-term kidney transplant survival has improved.

Sundaram Hariharan, MD, Professor of Medicine, and Director of Transplant Nephrology at the Medical College and Froedtert Hospital is the principal investigator of the study. Medical College co-authors are Christopher P. Johnson, MD, Professor of Surgery, and Barbara A. Bresnahan MD, Associate Professor of Medicine.

The team analyzed nearly 94,000 kidney transplants performed in the US between 1988 and 1996, using data from the United Network for Organ Sharing in Richmond, VA. Twenty percent of the recipients were African American and 24% of all transplants were from living donors.

"The good news is that long-term success after transplantation continues to improve," says Dr. Hariharan. "And, with the various new immunosuppressive agents available today, we will further enhance transplant success."

The number of patients with end-stage kidney disease in the US is increasing at the rate of 7 to 8% each year. About 12,000 kidney transplants are performed annually. Of these, 8,000 are from cadaver donors and 4,000 are from living donors. With more than 44,000 patients waiting for a kidney transplant, the gap between organ availability and need continues to grow.

The researchers looked at one-year post-transplant survival rates for all transplants from both living and cadaver donors. They found that one-year, living donor kidney transplant survival improved from 88.8 to 93.9%. The one-year survival rate for patients receiving a cadaver transplant improved from 75.7 to 87.7%.

While cyclosporine, an immunosuppressive drug introduced in the early 1980's, improved the rate of transplant survival at one year, it was thought that it did not substantially improve long-term transplantation survival, according to Dr. Hariharan. Chronic rejection is the most important cause of long-term transplant failure. However, the new study shows that long-term transplant survival had improved since 1988. This benefit is due to lower rates of acute rejections.

The 94,000 kidney transplants represent all transplants performed in the US between 1988 and 1996. Transplant survival was calculated for each of these individual years. Kidney transplant survival is assessed mathematically by half life in years. Half life is the estimated time for 50 % of transplants to develop failure, or conversely 50% to survive. This projected half life has increased for living donor transplants from 12.7 years in 1988 to 21.6 years in 1996, an increase of 70%. For cadaver transplants, half-life increased by 75%, from 7.9 years to 13.8 years.

According to Dr. Hariharan, the incidence of kidney failure is higher in African Americans than in whites, and the transplant survival rate is lower in African Americans. The long-term benefits in the current study included improved transplant survival in both whites and African Americans.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.