Sole DNMT3A/TET2/ASXL1 Mutations Define a Distinct Clinical Trajectory for Patients with Clonal Hematopoiesis

Background: Clonal hematopoiesis of indeterminate potential (CHIP) is a clinically defined entity that is recognized by the 2022 International Consensus Classification and the 5 th Edition of the WHO. While the Clonal Hematopoiesis Risk Score (CHRS) incorporates 8 variables that underlie a prognostic framework for prediction of risk for progression to myeloid neoplasm (MN) (Weeks LD et al., NEJM Evidence 2023), there remains debate as to the role of mutations in epigenetic regulators, such as DNMT3A, TET2 and ASXL1 (“DTA”), with respect to clinical outcomes in the real-world setting. Although DTA mutations often occur early in myeloid pathogenesis, the persistence of these mutations as age-related clonal hematopoiesis (CH) might not significantly influence clinical course (Jongen-Lavrencic M et al., NEJM 2018). We have previously observed impaired clearance of DTA-mutant clones with hypomethylating agent or intensive chemotherapy for myelodysplastic neoplasms and acute myeloid leukemia (ASH abstract 4122; Blood (2022) 140 (Supplement 1): 9150-9151), and we now seek to understand the impact of sole DTA mutations in patients with CH. Methods: We studied a pre-selected group of patients who had an indication for undergoing bone marrow evaluation. Such indications included cytopenia(s), elevated blood cell count(s), staging/workup for lymphoma, and radiographic marrow abnormalities. Patients with CH were identified via concurrent morphologic, cytogenetic, and molecular diagnostics of bone marrow aspirates reviewed by UMass and Stanford Hematopathology from 2013 to 2023. CH was defined as presence of a somatic mutation with variant allele frequency (VAF) ≥ 2% on molecular diagnostics or non-myelodysplastic syndrome (MDS)-defining clonal cytogenetic aberration in a patient without morphologic evidence of MN. A total of 79 patients with CH were identified, then segregated based on presence or absence of sole DTA mutations. Results: We assessed the clinical trajectory of patients with CH who did not exclusively have DTA mutations (“non-sole DTA;” n = 58) (Panel A) compared to patients with CH who had DTA mutations alone without any other concurrent mutations (“sole DTA;” n = 21) (Panel B). The median age at detection of CH for sole DTA vs. non-sole DTA was 71.0 ± 2.11 years vs. 71.5 ± 1.45 years, respectively ( p = 0.454). Median number of mutations for sole DTA vs. non-sole DTA patients was 1.24 ± 1.2 vs. 2.24 ± 0.18, respectively ( p < 0.0001). Median follow-up