Islet transplantation is now reimbursed in type 1 diabetes (T1D) in France. Long-term use of immunosuppressants represents a risk factor for neoplasia. 

Objective: To compare the frequency of solid cancers (including skin cancer) in T1D patients who have received islet or pancreatic transplants.

Patients and Methods: retrospective single-center study in a university diabetology department. Four groups of T1D patients were compared: islet transplant alone with the Edmonton protocol (ITA-Edm; n = 19), islet after kidney transplant with the Edm protocol (IAK-Edmonton; n = 14), islet transplant alone with induction by anti-lymphocyte antibodies (ITA-ATG; n = 16); combined kidney-pancreas transplant with induction by anti-lymphocyte antibodies (SPK-ATG; n=14)

Results: The age of the patients during the pre-transplant assessment varied between 31 and 64 years, similar between the 4 groups. The number of years of follow-up after islet or pancreas transplant varied between 3 and 28 years, more prolonged in patients who received an Edmonton protocol (more than 10 years on average). Six deaths were observed in these 63 patients: 4 in the IAK-Edm group (vascular cause in 2 patients, infectious in one and in the aftermath of a cutaneous lymphoma considered to be cured in the 4th, over 10 years after islet transplantation); two deaths in the SPK-ATG group (including one from cancer), respectively 13 and 28 years post-transplant. These patients had no other cancer. The number of patients who presented with skin cancer (sometimes multiple) was 3/14 patients in the IAK-Edm group (3 squamous cell carcinomas, 1 basal cell, 3 Bowen's diseases), 4/19 in the ITA-Edm group (1 squamous cell, 1 basal cell ; 2 Bowen's diseases), 4/16 in the ITA-ATG group (2 squamous cell, 3 basal cell), and 1/14 in the kidney-pancreas group (1 basal cell). Otherwise, two adenocarcinomas of the rectosigmoid hinge were diagnosed in the latter group, resulting in death in one of the 2 cases. All skin cancers progressed favorably.

Discussion: The number of deaths is higher in the IAK patients, who are the most fragile. Skin cancers - progressing favorably - seem to be more common in the islet transplant groups than in the kidney-pancreas group, possibly due to the multiple inductions. Colonic cancers, on the other hand, are more frequent and more serious in combined SPK transplants, justifying careful screening. Given the duration of follow-up, the least-risk patients seem to be the islet transplant alone with the Edmonton protocol, perhaps because of the less powerful and fewer inductions, the lack of use of etanercept and the potentially protective effect of sirolimus.