Impact of Tacrolimus, Sirolimus, Age, and Body Mass Index on the Occurrence of Skin Cancer and Islet Dysfunction After Transplantation

Herein, we characterized the percentage of tacrolimus to the combined sirolimus and tacrolimus trough levels (tacrolimus %) observed during islet transplant-associated immune suppression therapy with post-transplant skin cancer. Although trough levels of tacrolimus and sirolimus were not different (<i>P</i> = 0.79, 0.73, respectively), high tacrolimus % resulted in a 1.32-fold increase in skin cancer odds when adjusting for age, sex, body mass index (BMI), and use of mycopheonlate mofetil (MMF; <i>p</i> = 0.039). Skin cancer patients were likely to have been older but not differ significantly (mean difference 12 years, <i>P</i> = 0.056), but age was significantly associated with a 1.22-fold increase in adjusted skin cancer odds (<i>P</i> = 0.046). BMI was inversely associated with skin cancer, with an adjusted odds ratio (OR) of 0.40 (<i>P</i> = 0.022). High tacrolimus % (>35) resulted in a 4.6-fold increase in skin cancer frequency, whereas sirolimus above 75% of the combined therapy led to a 5.2-fold increase in islet graft dysfunction (IGD) events/year. By calculating the maximum safe exposure (MSE) to tacrolimus % according to patient age and BMI, we found that cumulative months spent above MSE was predictive of skin cancer (1.20-fold increase, <i>P</i> = 0.003). Individuals exceeding the MSE for 1 year were 9.2 times more likely to develop skin cancer (<i>P</i> = 0.008). Results suggest that strategies targeting immunosuppression ratios based on age and BMI may minimize cancer risk while improving graft survival and function.