Clinical Outcomes of Clonal Hematopoiesis in Renal Transplant Recipients
Authors: Harris Zoey I. , Mour Girish , Arana Yi Cecilia Y. , Schinstock Carrie , Attieh Rose Mary , Leung Nelson , Shah Surbhi 
Published: December 2024

Introduction
Clonal hematopoiesis (CH) in solid organ transplant (SOT) recipients can lead to impaired tolerance to immunosuppressive therapy, increased risk for complications, and potentially compromise graft and patient outcomes. The impact of mutational profile in CH on risk for hematological transformation and patient/graft outcomes for kidney transplant (KT) recipients is largely unknown. Our aim was to assess the prevalence of CH and progression of CH in KT, evaluate the impact of CH on allograft function, assess patient outcomes and determine Clonal Hematopoietic Risk Score status.
Methods
We retrospectively reviewed the CH profile of patients 18+ years of age who received a kidney transplant at Mayo Clinic Enterprise between 01/01/1994-12-31/2022 and underwent bone marrow biopsy with aspirate pre- and/or post-transplant. Bone marrow biopsies were primarily performed post-transplant in the workup for cytopenias. Transplant database was used to collect our variables of interest including post-transplant malignancy and outcomes. CH was ascertained through next-generation sequencing (NGS) on bone marrow samples. A 47-gene panel was utilized in our study. CH was defined by presence of somatic mutation with a variant allele frequency of &gt; 2.0%. CH in absence of cytopenias was classified as CHIP while CH in individuals with one or more cytopenias was classified as clonal cytopenias of undetermined significant (CCUS). The Clonal Hematopoiesis Risk Score (CHRS) was utilized for CHIP and CCUS risk stratification We excluded the patients who had a prior hematologic malignancy.
Results
305 kidney transplant recipients met our study criteria. The median time to follow up, defined as time from transplant until first bone marrow biopsy with evidence of CH, was 46.1 months.
The frequency of CH in kidney recipients was 27/305 (9.0%), of these 14/27 (52%) patients were found to have CCUS and 10/27 (37%) were found to have evidence of post-transplant myeloid malignancy. Of these cases, 5/10 (50%) developed acute myeloid leukemia while 5/10 (50%) developed myelodysplastic syndrome. Both CCUS and myeloid neoplasms were more common in female patients, accounting for 8/14 (57%) and 7/13 (54%) of each cohort, respectively.
Amongst CCUS, the most frequent mutations were seen in ASXL1, DNMT3A and TET2. More than half of patients with CH, 14/27 (52%), exhibited mutations in 2 or more genes. Meanwhile, in cases of myeloid malignancy, the commonly mutated genes were ASXL1 and TP53, seen in 3/10 and 3/10 cases, respectively.
The CCUS risk status was intermediate, with median score of 11.8 (range 9.5-14). One CCUS patient transformed to myelodysplastic syndrome. The time to progression from CCUS to myelodysplastic syndrome was 14.3 months and their respective CHRS status was determined to be high-risk.
Infectious complications, including viral and opportunistic infections, were seen in 12/27 (44%) recipients with CH, with CMV viremia being the most common, followed by BK viremia. In this cohort, post-transplant cardiovascular events and venous thromboembolic events occurred in 2/27 (7.0%) and 7/27 (26%) patients, respectively. Allograft failure was seen in 17/27 (63%) recipients at a median of 93.4 months post-transplant. After a median of 122 months, there were 14/27 (52%) deaths at a median duration of 93.4 months post-transplant. Causes of mortality included myeloid malignancy, infection, cardiovascular complications, end-stage renal disease or were unknown.
Conclusions
Renal transplant recipients carry mutations in epigenetic regulators resulting in adverse outcomes. Similar to the general population, DNMT3A, TET2 and ASXL1 mutations were the most common mutations in post-transplant CCUS. Infections, cardiovascular events, and allograft failure were frequent. Prospective studies in a larger cohort are needed to evaluate the impact of CCUS in survival and myeloid malignancy transformation risk.