Risk of Kaposi sarcoma after solid organ transplantation in the United States.

Due to treatment with immunosuppressive medications, solid organ transplant recipients have elevated risk for Kaposi sarcoma (KS), which is caused by human herpesvirus 8 (HHV8). Other risk factors for KS are poorly understood. We linked the United States solid organ transplant registry with 17 population-based cancer registries to ascertain KS incidence among 244,964 transplant recipients from 1987-2014. To compare incidence rates of KS according to patient and transplant characteristics, we calculated incidence rate ratios (IRRs) using Poisson regression. To compare associations of KS with other skin cancers occurring before or within 12 months of KS diagnosis, we computed odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression. All statistical tests were two-sided. We identified 163 KS cases during follow-up. Among transplant recipients, we found significantly increased risk of KS associated with male sex (IRR = 1.87; 95%CI:1.32,2.71), nonwhite race (IRR = 2.67; 95%CI:1.92,3.72), non-US citizenship (IRR = 2.10; 95%CI:1.19,3.47), lung transplant (IRR = 2.22; 95%CI:1.03,4.24, vs. kidney), and older age at transplant. KS risk decreased significantly with time since transplant and recent calendar year, however, no specific induction or maintenance medication was associated with KS. KS incidence was not significantly associated with ambient ultraviolet radiation (IRR = 1.32 95%CI:0.87,2.02, tertile 3 vs. 1). KS incidence has decreased in recent calendar years. In a cross-sectional sample, we found cutaneous squamous cell carcinoma was associated with KS (OR = 4.83; 95%CI:1.30,14.69). KS risk factors included those potentially associated with HHV8 infection and increased immunosuppression. Our findings suggest that transplant recipients with a non-KS skin cancer may also be at high KS risk.