A model for dropout assessment of candidates with or without hepatocellular carcinoma on a common liver transplant waiting list

Abstract

In many countries, the allocation of liver grafts is based on the Model of End-stage Liver Disease (MELD) score and the use of exception points for patients with hepatocellular carcinoma (HCC). With this strategy, HCC patients have easier access to transplantation than non-HCC ones. In addition, this system does not allow for a dynamic assessment, which would be required to picture the current use of local tumor treatment. This study was based on the Scientific Registry of Transplant Recipients and included 5,498 adult candidates of a liver transplantation for HCC and 43,528 for non-HCC diagnoses. A proportional hazard competitive risk model was used. The risk of dropout of HCC patients was independently predicted by MELD score, HCC size, HCC number, and alphafetoprotein. When combined in a model with age and diagnosis, these factors allowed for the extrapolation of the risk of dropout. Because this model and MELD did not share compatible scales, a correlation between both models was computed according to the predicted risk of dropout, and drop-out equivalent MELD (deMELD) points were calculated. Conclusion: The proposed model, with the allocation of deMELD, has the potential to allow for a dynamic and combined comparison of opportunities to receive a graft for HCC and non-HCC patients on a common waiting list. (HEPATOLOGY 2012;56:149-156) S ince the publication of the Milan selection criteria in 1996, liver transplantation has been recognized as the best treatment for selected patients with nonresectable hepatocellular carcinoma (HCC). 1Over the years, HCC has become one of the main indications for liver transplantation as a result of the combined effects of an increasing incidence of new HCC cases (matching the incidence of hepatitis C infection) and the use of more extended selection criteria.2-4 These factors combined exert an increasing pressure on the limited liver donor pool.Access to transplantation for HCC and non-HCC patients is granted on the basis of different approximations of utility. In nonmalignant patients, utility is represented by transplantation benefit (i.e., survival compared to death), whereas HCC patients are selected according to a longer term utility perspective (Milan: expected 5-year survival over 70%). The Model for End-Stage Liver Disease (MELD) score allows for the selection and priority transplantation of patients with the highest short-term risk of death. 5,6 Because most HCC candidates maintain relatively good liver function, they are poorly served (and infrequently transplanted) with the use of the raw MELD score; as such, ''exception'' points that increase their priority ranking have been artificially allocated. Originally, U.S. patients within Milan criteria (single HCC 5 cm in diameter and 3 HCCs 3 cm) were attributed 24

Model for End-stage Liver Disease

“…For example, two patients with similar MELD scores would be given different exception points based on their drop out risk from the waiting list after considering factors such as number of tumors, maximum tumor size, age of the patient, etiology of liver disease, and AFP levels. 55 …”

A Multistep, Consensus-Based Approach to Organ Allocation in Liver Transplantation: Toward a “Blended Principle Model”

“…The latter can be considered prototypic MELD exceptions because a MELD-based system fails to capture their risk of dropout due to tumor progression or liver-related complications with no bearing on MELD score (4). The appropriate selection of candidates with or without HCC for LT, and their priority on the waiting list, therefore cannot be achieved with models based on urgency alone (Appendix 1).…”

Current advances made in the surgical treatment of hepatocellular carcinoma

“…Different models have been developed to quantify the risk of death in neoplastic and nonneoplastic patients. 89,92 As the neoplastic risk assessment is not considered in MELD scoring, patients with unresectable HCC within the MC have been considered exceptions in the American allocation system. Patients with HCC fulfilling the MC enter the waiting list with a MELD score equal to 22 and receive incremental points for every three months spent on the waiting list.…”