Validation of the R3-AFP model for risk prediction of HCC recurrence after liver transplantation in the SiLVER randomized clinical trial

Explant-based models for assessing HCC recurrence after liver transplantation serve as the gold standard, guiding post-liver transplantation screening and immunosuppression adjustment. Incorporating alpha-fetoprotein (AFP) levels into these models, such as the novel R3-AFP score, has notably enhanced risk stratification. However, validation of these models in high-evidence data is mandatory. Therefore, the aim of the present research was to validate the R3-AFP score in a randomized clinical trial. We analyzed the intention-to-treat population from the 2-arm SiLVER trial (NCT00355862), comparing calcineurin-based ([calcineurin inhibitors]-Group A) versus mammalian target of rapamycin inhibitors-based (sirolimus-Group B) immunosuppression for post-liver transplantation HCC recurrence. Competing risk analysis estimated sub-hazard ratios, with testing of discriminant function and calibration. Overall, 508 patients from the intention-to-treat analysis were included (Group A, n = 256; Group B, n = 252). The R3-AFP score distribution was as follows: 42.6% low-risk (n = 216), 35.7% intermediate-risk (n = 181), 19.5% high-risk (n = 99), and 2.2% very-high-risk (n = 11) groups. The R3-AFP score effectively stratified HCC recurrence risk, with increasing risk for each stratum. Calibration of the R3-AFP model significantly outperformed other explant-based models (Milan, Up-to-7, and RETREAT), whereas discrimination power (0.75 [95% CI: 0.69; 0.81]) surpassed these models, except for the RETREAT model (p = 0.49). Subgroup analysis showed lower discrimination power in the mammalian target of rapamycin group versus the calcineurin inhibitors group (p = 0.048). In conclusion, the R3-AFP score accurately predicted HCC recurrence using high-quality evidence-based data, exhibiting reduced performance under mammalian target of rapamycin immunosuppression. This highlights the need for further research to evaluate surveillance schedules and adjuvant regimens.