Transplanting a mismatched kidney from a living donor may lower the risk of death more than not doing a transplant at all, according to a new study that could open the door to more operations.

A long-term study found that transplant recipients whose immune systems were technically incompatible to the donated kidney — because they had so-called anti-HLA antibodies — were more likely to be alive eight years later than people who did not receive a transplant or waited to get an organ from a deceased donor.

"We used to say if you had a compatible donor, you could do a transplant. Now you can say, if you have an incompatible donor, we still can make that transplant happen," senior author Dr. Dorry Segev of John Hopkins University in Baltimore told Reuters Health. "That's very exciting to those on the waiting list."

Eight-year survival rates were almost 77 per cent for 1,025 people who received an HLA-incompatible kidney from a live donor, 63 per cent for 5,125 matched patients who remained on a waiting list for a kidney or received a kidney from a deceased donor and 44 per cent for 5,125 people who remained on the waiting list without receiving a kidney.

"The paper is showing how much longer the patient will live compared to their next available option," said Segev, who directs John Hopkins' Epidemiology Research Group in Organ Transplantation.

"Your next best option is waiting on the list for a compatible donor, and a lot of those patients will never find one."

All about timing

The study was done at 22 centres. It could help the more than 32,000 people in the United States who have anti-HLA antibodies and need a transplant.

"It's all about timing," said Dr. Sanjay Kulkarni, director of kidney and pancreas transplantation at Yale-New Haven Hospital and the Yale School of Medicine, who was not involved in the research.

"The longer people are on dialysis before they have a transplant, the worse their survival," he said. "So if you have a living donor, instead of waiting five years for a compatible donor, if you can get a transplant from an incompatible donor in a couple of months, this paper suggests that that is beneficial, despite the fact that they have a higher rate of rejection," he told Reuters Health.

If you have an incompatible donor, we still can make that transplant happen. - Dr. Dorry Segev

"The implications of these results are revolutionary, especially when the numerous contradictory opinions raised by the transplant community are considered," said Drs. Lionel Rostaing and Paolo Malvezzi of the Centre Hospitalier Universitaire Grenoble Alpes in La Tronche, France, in an editorial accompanying the study in the New England Journal of Medicine.

Desensitizing recipients can be very expensive, they said, and the immunosuppressive regimens required carry the potential of infection and cancer.

In addition, living donors face a small but significant increase in their risk of end stage renal disease.

Nonetheless, Rostaing and Malvezzi write, using incompatible kidneys from living donors "may save lives and may be cost-effective over time."

There is an added cost, but it is relatively small, Segev said.

Each patient's immune system has to be desensitized to accept the incompatible kidney.

Depending on antibody levels, "it can take a few days to a couple of weeks," he said. "But compared to the cost of a transplant, it's relatively low. If a transplant costs perhaps $100,000 and you add desensitization, it might be $110,000 to $120,000." There's the additional cost of $10,000 or so each year for drugs to keep the immune system from rejecting the kidney. "But compared to $100,000 a year for dialysis," he said, a transplant quickly becomes cost effective over time.

Kulkarni cautioned that the organ donation system was changed just over two years ago to make it easier for hard-to-match patients to get a kidney from a deceased donor.

Now "people are getting transplanted much quicker" so today's survival rates may not be as dramatically different as they are in the new study, he said. "But I bet they still hold."