The arrival of a new generation of drug therapies is helping transplanted kidneys keep working longer, claims research.
Transplanted organs may only last a few years
In particular doctors may now been able to stop using a drug which while it prevented rejection of the new organ could, it is suggested, hasten its failure with its toxic side-effects.
But experts at a leading kidney research charity say it is too early to abandon the drug, ciclosporin, and urged patients taking the drug not to worry.
Most kidney transplant patients in the UK are currently on a regime that includes ciclosporin.
Transplant patients have to take drugs for life after they receive their new organ.
This is because the body's immune system would normally recognise the new kidney or heart as a foreign "invader", and launches a massive attack on it.
The drug regime is designed to suppress the immune system and damp down this effect.
But long-term immune suppression is a less than ideal situation.
Between 6% and 8% of transplant recipients develop cancer as a result of the drugs.
In addition ciclosporin is known to cause kidney toxicity which can damage the organ and cause it to fail within a decade.
Many patients require a second, or even a third transplant operation in their lifetime.
Thousands are currently waiting for organs - only a quarter of patients get an operation within a year of going on the waiting list.
Newer combinations of anti-rejection drugs have been under test here and in the US.
These include Rapamune, which some experts believe can perform the same task as ciclosporin - minus some of its unwanted side-effects.
The world's largest "ciclosporin withdrawal" trial, involving more than 400 patients, has been running for three years.
Kidney function was tested in "traditional" ciclosporin regime patients, and in patients getting a combination of Rapamune and steroids.
They found the tests suggested that the organs were working better in the patients given the new combination.
There was also a slight fall in the number of kidneys that failed following transplant - and patients reported feeling better in the Rapamune group.
Death rates in the two groups were roughly the same, as was actual immune rejection of the kidney, but blood pressure was better in the patients given the newer treatment.
Professor Peter Friend, from the Nuffield Department of Surgery at the University of Oxford, said: "There are many factors that cause long-term progressive injury to transplanted kidneys and these cause more transplanted kidneys to fail than acute rejection.
"Of the 1,691 kidneys transplanted in 2001, 15% were second and third transplants in patients who had previously lost a transplant.
"These data show that elimination of ciclosporin and long term maintenance of patients on Rapamune and steroids does lead to improvements in graft function."
While the results are the best so far for an alternative to ciclosporin, there is no proof so far that kidneys maintained this way will last any longer than those in ciclosporin patients.
The National Kidney Research Fund cautioned against rushing too fast towards the newer drug.
A spokesman told BBC News Online: "The Fund would like to reassure patients taking ciclosporin as an immuno-suppressant drug not to be alarmed by the news that due to its side effects it should be replaced by newer drugs.
"Due to the early days of the research and the fact that ciclosporin has been well established for many years, the Fund believes that it is premature to advise people not to take ciclosporin."
The study results were presented at a conference of transplant surgeons in the US.