For recipients of liver transplantations (LTs) for hepatocellular carcinoma (HCC), HCC recurrence after transplantation remains a major concern. Sirolimus (SRL), an immunosuppressant with anticarcinogenic properties, may reduce HCC recurrence and improve survival. In our study, the US Scientific Registry of Transplant Recipients was linked to pharmacy claims. For liver recipients transplanted for HCC, Cox regression was used to estimate associations of early SRL use with recurrence, cancer-specific mortality, and all-cause mortality, adjusting for recipient ethnicity, calendar year of transplant, total tumor volume, alpha-fetoprotein, transplant center size, use of interleukin 2 induction therapy, and allocated and calculated Model for End-Stage Liver Disease score. We performed stratified analyses among recipients who met Milan criteria, among those without renal failure, among those with deceased liver donors, by age at transplantation, and by tumor size. Among the 3936 included HCC LTs, 234 (6%) were SRL users. In total, there were 242 recurrences and 879 deaths, including 261 cancer-related deaths. All-cause mortality was similar in SRL users and nonusers (adjusted hazard ratio [aHR], 1.01; 95% CI, 0.73-1.39). HCC recurrence and cancer-specific mortality rates appeared lower in SRL users, but associations were not statistically significant (recurrence aHR, 0.86; 95% CI, 0.45-1.65; cancer-specific mortality aHR, 0.80; 95% CI, 0.43-1.50). Among recipients >55 years old, associations were suggestive of better outcomes for SRL users (all-cause mortality aHR, 0.62; 95% CI, 0.38-1.01; recurrence aHR, 0.52; 95% CI, 0.19-1.44; cancer-specific mortality aHR, 0.34; 95% CI, 0.11-1.09), whereas among recipients ≤55 years old, SRL users had worse outcomes (all-cause mortality aHR, 1.76; 95% CI, 1.12-2.75; recurrence aHR, 1.49; 95% CI, 0.62-3.61; cancer-specific mortality aHR, 1.54; 95% CI, 0.71-3.32). In conclusion, among HCC liver recipients overall, SRL did not appear beneficial in reducing all-cause mortality. However, there were suggestions of reductions in recurrence and cancer-specific mortality, and effects appeared to be modified by age at transplantation.
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