Donor-Derived Cell-Free DNA as a Prognostic Biomarker After Heart Transplantation

BACKGROUND: Measurement of donor-derived cell-free DNA fraction (dd-cfDNA%) and donor quantity score (DQS) is a noninvasive biomarker of acute rejection in heart transplantation (HT). Its prognostic value beyond histopathology remains uncertain. OBJECTIVES: This study sought to evaluate associations between donor-derived cell-free DNA (dd-cfDNA) and clinically meaningful outcomes using a composite endpoint of treated rejection, graft dysfunction, retransplantation, or death within 1 year post-HT. METHODS: The DEFINE-HT (Development of Noninvasive Cell-free DNA to Supplant Invasive Biopsy in Heart Transplantation) was a prospective, observational study following adult HT recipients at 10 U.S. centers for 1-year post-HT; blood was collected for dd-cfDNA testing (Prospera Heart) during surveillance and for-cause evaluations, independent of clinical decision-making. Treated rejection included biopsy-positive or biopsy-negative rejection requiring augmented immunomodulation. Graft dysfunction was defined as >10% decline in left ventricular ejection fraction from baseline to <50%. Time-varying Andersen-Gill models assessed associations between dd-cfDNA and events. RESULTS: Among 110 patients (median age 55 years, 25.5% female, 22% Black), 38 (34.5%) met the primary composite endpoint: treated rejection (20%), graft dysfunction (10.9%), death (3.6%), and retransplantation (0%). Furthermore, 4.6% of endomyocardial biopsies demonstrated rejection and 90% of dd-cfDNA results were below threshold. dd-cfDNA% and DQS were higher in treated vs untreated biopsy-positive rejection (0.23% vs 0.085%; P = 0.045, and 27 vs 9 copies/mL; P = 0.012, respectively). No patients with graft dysfunction had biopsy-positive rejection despite elevated dd-cfDNA. One-intrapatient-SD increases in dd-cfDNA% and DQS were associated with 19% and 12% higher risk of the primary endpoint (P < 0.001). Above-threshold dd-cfDNA levels also conferred 4.42-fold increased risk of the composite endpoint (P < 0.001). CONCLUSIONS: DEFINE-HT supports the potential role of dd-cfDNA as a prognostic biomarker of graft health and informs a randomized trial comparing dd-cfDNA and biopsy-based monitoring. (Development of Noninvasive Cell-free DNA to Supplant Invasive Biopsy in Heart Transplantation [DEFINE-HT]; NCT05309382).