Immunosuppression regimen and latitude impact keratinocyte carcinoma risk in US liver transplant recipients

Immunosuppression after solid organ transplantation is associated with an increased risk of keratinocyte carcinoma (KC). Despite its established morbidity, KC risk in liver transplant (LT) recipients is understudied, including the contribution of immunosuppression regimen and latitude. A retrospective cohort of 9,966 adult first LT alone recipients alive with their native allograft at 1-year post-LT without prior KC between 2007 and 2016 were identified using linked data from the Organ Procurement and Transplantation Network and Medicare administrative claims. The primary exposures were immunosuppression regimen and latitude of residence. The primary outcome was incident, de novo KC occurring at least 1-year after LT. Adjusted Cox regression analysis stratified by transplant center was used in all analyses. The cohort was 63.4% male, 70.2% White and with median age 61 years (interquartile range, IQR, 54-66) at transplant. Calcineurin inhibitor (CNI) with anti-metabolite combination was independently associated with incident KC when measured as intention-to-treat (adjusted hazard ratio (aHR) 1.21 vs. CNI monotherapy, 95% CI 1.02-1.43, p = 0.026), in a time-updating as-treated analysis (aHR 1.61, 95% CI 1.34-1.93; p < 0.001) and when measured as cumulative exposure (aHR 1.13 per 6-month increase, 95% CI: 1.02-1.33; p = 0.027). More southern latitude of residence was also independently associated with incident KC with an aHR of 1.26 per 5 degrees N decrease towards the Equator (95% CI: 1.08-1.47, p = 0.003). We demonstrate independent effects of CNI with antiM immunosuppression regimen and latitude of residence on the risk of post-LT KC, which will better inform screening practices and immunosuppression management.