Validation of the Revised Pretransplant Assessment of Mortality Score in Patients with Acute Myelogenous Leukemia Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Abstract

Despite recent advances, allogeneic hematopoietic stem cell transplantation (allo-HSCT) continues to be accompanied by a high rate of morbidity and mortality. Several scores have been developed to predict outcome after allo-HSCT. The recently revised Pretransplant Assessment of Mortality (PAM) score is based on patient age, donor type, disease risk, cytomegalovirus (CMV) serostatus of patient and donor, and forced expiratory volume in 1 second (FEV₁). The aim of this study was to analyze the predictive power of the PAM score in an independent large cohort of patients with acute myelogenous leukemia (AML). We selected adult patients with AML who underwent a first allo-HSCT at the University Hospital of Dresden, a tertiary care hospital with a large transplantation program. All adult patients treated between January 1, 2003, and July 1, 2015, were included. The PAM score was calculated as described previously. Overall survival (OS), cumulative incidence of relapse (CIR), and nonrelapse mortality (NRM) after allo-HSCT were analyzed. Age, AML type, sex match, CMV match, donor type, European Leukemia Net risk classification, type of conditioning, disease stage, and PAM score as a continuous variable were selected a priori for multivariate Cox regression analyses. A total of 544 patients met the inclusion criteria. The median patient age was 57 years. With a median follow-up of 47 months (range, 1 to 161 months), the estimated OS for the whole cohort at 4 years was 43%, with a CIR of 30% and an NRM of 31%. The probability of OS at 4 years was 65% for patients with a PAM score of 0, 52% in those with a PAM score of 1, 33% in those with a PAM score of 2, and 22% in those with a PAM score of 3 (P < .001, log-rank test). Both the CIR and NRM increased with higher PAM scores (P = .005 and P < .001, respectively, Gray test). In multivariate analysis, age (hazard ratio [HR], 1.02 per year; P = .004), disease stage (primary induction failure versus first complete remission (CR1); HR, 1.5; P = .03), and the PAM score (HR 1.04; P = .03) had a significant impact on OS. This is the first independent validation of the revised PAM score allowing for simple and valid estimation of transplantation outcomes. It can serve as an important tool in counseling patients with AML, as well as in designing future trials.

Keywords: AML; Comorbidities; PAM score.