Clinical phenomapping and outcomes after heart transplantation

BACKGROUND

Survival after heart transplantation (HTx) is limited by complications related to alloreactivity, immune suppression, and adverse effects of pharmacologic therapies. We hypothesize that time-dependent phenomapping of clinical and molecular data sets is a valuable approach to clinical assessments and guiding medical management to improve outcomes.

METHODS

We analyzed clinical, therapeutic, biomarker, and outcome data from 94 adult HTx patients and 1,557 clinical encounters performed between January 2010 and April 2013. Multivariate analyses were used to evaluate the association between immunosuppression therapy, biomarkers, and the combined clinical end point of death, allograft loss, retransplantation, and rejection. Data were analyzed by K-means clustering (K = 2) to identify patterns of similar combined immunosuppression management, and percentile slopes were computed to examine the changes in dosages over time. Findings were correlated with clinical parameters, human leucocyte antigen antibody titers, and peripheral blood mononuclear cell gene expression of the AlloMap (CareDx, Inc., Brisbane, CA) test genes. An intragraft, heart tissue gene coexpression network analysis was performed.

RESULTS

Unsupervised cluster analysis of immunosuppressive therapies identified 2 groups, 1 characterized by a steeper immunosuppression minimization, associated with a higher likelihood for the combined end point, and the other by a less pronounced change. A time-dependent phenomap suggested that patients in the group with higher event rates had increased human leukocyte antigen class I and II antibody titers, higher expression of the FLT3 AlloMap gene, and lower expression of the MARCH8 and WDR40A AlloMap genes. Intramyocardial biomarker-related coexpression network analysis of the FLT3 gene showed an immune system-related network underlying this biomarker.

CONCLUSIONS

Time-dependent precision phenotyping is a mechanistically insightful, data-driven approach to characterize patterns of clinical care and identify ways to improve clinical management and outcomes.

Thrombotic microangiopathy associated with sirolimus level after allogeneic hematopoietic cell transplantation with tacrolimus/sirolimus-based graft-versus-host disease prophylaxis

Posttransplantation thrombotic microangiopathy (TMA) is a multifactorial complication of allogeneic hematopoietic cell transplantation (allo-HCT) whose incidence is increased with the use of a sirolimus plus tacrolimus (SIR/TAC) regimen for acute graft-versus-host disease (aGVHD) prophylaxis. We evaluated the incidence and possible risk factors for TMA in a case series of 177 patients who received allo-HCT using SIR/TAC-based GVHD prophylaxis. The patients received either a sibling donor graft (n = 82) or a matched unrelated donor graft (n = 95). Within the first 100 days post-HCT, 30 patients (17%) were diagnosed with TMA, and an additional 9 patients (5%) were classified as probable TMA cases. The median time to onset of TMA was 4.6 weeks (range, 1.6-10.6 weeks). Thirty-four patients developed both TMA and aGVHD, with the majority (81%) developing aGVHD first. Multivariate analysis identified the following factors as associated with increased risk of TMA: day 14 serum sirolimus level ≥9.9 ng/mL (hazard ratio [HR], 2.19; 95% confidence interval [CI], 1.13-4.27; P = .02), presence of previous aGVHD grade II-IV (HR, 3.04; 95% CI, 1.38-6.71; P < .01), and fully myeloablative conditioning (HR, 3.47; 95% CI, 1.60-7.53; P < .01). These risk factors for TMA suggest that when using a SIR/TAC regimen for GVHD prophylaxis, careful monitoring and adjustment of the sirolimus dosage is critical, particularly in patients with active aGVHD.