medwireNews: Three-quarters of people who undergo islet transplantation for type 1 diabetes have sustained graft survival with associated improvements in glucose control, insulin requirements, and hypoglycemia incidence 10 years later, research shows.
And 28% remained completely independent of exogenous insulin, report Marie-Christine Vantyghem (University of Lille, France) and co-researchers in Diabetes Care.
The team followed up 28 people with type 1 diabetes who underwent islet transplantation as part of two phase II studies.
All study participants were able to stop insulin treatment after transplantation, but the proportion retaining insulin independence fell to 39% after 5 years and to 28% after 10 years. The researchers note that the likelihood of this outcome did not significantly differ between the 14 patients who had an islet transplant in isolation and the 14 who had it after a kidney graft.
“Preexisting immunosuppression and a lower BMI may have contributed to these favorable results” in people with a prior kidney graft, they say, and suggest that pancreas or islet transplantation should be discussed with any person with type 1 diabetes who is due to undergo a kidney transplant.
For all participants, primary graft function, evaluated 1 month after the last islet infusion, was a key predictor of sustained insulin independence, with other predictors being female sex, longer duration of diabetes, and the total mass of islet infusion.
Indeed, the median duration of insulin independence was 6 years among people with optimal primary graft function, compared with just 0.4 years among those with poorer function. And the corresponding median durations of graft survival were 10.0 versus 4.5 years; the 10-year Kaplan-Meier estimate of graft survival was 78%.
However, even those with less successful transplants benefited from the procedure; among all participants the median number of severe hypoglycemic events in the previous year fell from two at baseline to zero throughout follow-up.
The percentage of time spent in hypoglycemia also significantly improved, as did mean glucose, glucose variability, glycated hemoglobin level, and exogenous insulin requirement. Although these measures tended to deteriorate over time, at 10 years they remained significantly improved versus pre-transplantation.
Between 1 and 10 years after transplantation, there were eight serious adverse events related to immunosuppression (infections and skin carcinomas) and 11 diabetes-related events, six of which were asymptomatic myocardial ischemia and detected at the participants’ annual screenings.
All five symptomatic cardiovascular events occurred in people who underwent kidney graft and islet transplantation having been refused combined kidney and pancreas transplantation because of severe pre-existing diabetes complications.
And the researchers observe that “the overall risk profile of intraportal islet infusion observed in the current study appears lower than reported after pancreas transplantation.”
One patient died of a stroke during follow-up, giving a mortality rate of 0.3% per 100 person–years, which the researchers say is similar to that seen among people with type 1 diabetes who have few or no complications and without immunosuppression in the DCCT.
By comparison, the reported mortality rate in patients similar to those in the current study but who did not undergo islet transplantation is three to four times higher, they say, with causes of death largely being severe hypoglycemia or ischemic heart disease.
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