A Large Cohort Study of 412 Patients with SRSF2/TET2 Co-Mutated Myeloid Neoplasms: The Molecular Landscape and Clinical Outcomes

Introduction: Serine and arginine-rich splicing factor 2 (SRSF2) and tet methylcytosine dioxygenase 2 (TET2) are early mutations that drive the development of myeloid neoplasms and monocytosis. SRSF2/TET2 co-mutations are most common in chronic myelomonocytic leukemia (CMML). However, they can also be seen in myelodysplastic syndrome (MDS), acute myeloid leukemia from CMML (AML-CMML), other AML (AML-Other, mostly de novo AML), and myeloproliferative neoplasms (MPN). Previous studies have investigated these co-mutations in myeloid diseases separately and as a subset (CMML) or small subset (MDS or AML) of the patients. Additionally, these studies mainly compared the clinical difference between patients with and without these double mutations. A large cohort study of patients with both mutations, irrespective of the morphologic diagnosis, has not been reported.

Methods: Out of the Moffitt NextGen sequencing database of more than 8000 patients, we identified 412 patients with both SRSF2 and TET2 mutations and with diagnosed or suspected myeloid neoplasms. The demographics and clinical parameters were collected. Overall survival (OS) was defined as the time from sequencing to the last visit at Moffitt or death. Two experienced hematopathologists confirmed the final diagnosis according to the 5^th edition of the World Health Organization classification of hematological malignancies. Chi-squared tests of independence were used to compare the association between gene mutation and diagnosis, and a post hoc test based on adjusted standardized residuals was used. Cox proportional hazards models were used to compare the OS within and across diagnoses and included gender, age, gene mutation, and diagnosis (when comparing across diagnoses) as covariates.

Results: Of the 412 patients, 284 (69%) were male, 128 (31%) were female, and the average age was 75 years. The five most common diagnoses, in descending order, were CMML (41%), AML-Others (23%), MDS (12%), AML-CMML (9%), and MPN (6%). The ten most common additional mutated genes, in descending order, were ASXL1 (44%), RUNX1 (28%), CUX1 (13%), JAK2 (13%), CBL (11%), TP53 (10%), SETBP1 (9%), KRAS (9%), STAG2 (9%), and NRAS (9%). A comparison of the top 5 diagnoses and the top 10 additional gene mutations showed an association between diagnosis and gene mutation (chi2 = 131, 36 df, p=.000). A post hoc test showed CBL mutations were less frequent in patients with AML-Others (p=.029), STAG2 mutations were less common in CMML patients (p=.007), and STAG2 mutations were more frequent in patients with MDS (p=.000). Among all patients, RUNX1 mutation (HR=2.4, 95% CI [1.3, 4.4], p=.005), ASXL1 mutation (HR=2.3, 95% CI [1.3, 4.2], p=.005), and CBL mutation (HR=2.0, 95% CI [1.0, 3.8], p=.048) were associated with lower OS. Among patients diagnosed with CMML, KRAS mutation (HR=4.1, 95% CI [1.5, 11.3], p=.006) and ASXL1 mutation (HR=3.3, 95% CI [1.4, 8.3], p=.009]) were associated with lower OS. Among patients with low-grade myeloid diseases (CMML and MDS), ASXL1 mutation (HR=2.6, 95% CI [1.2, 5.9], p=.021) was associated with lower OS. For the five most frequently co-mutated genes (ASXL1, RUNX1, CUX1, JAK2, and CBL), no difference in OS was found between patients with CMML vs MDS, or AML-CMML vs AML-Others.

Conclusions: SRSF2 and TET2 co-mutations occurred in various myeloid diseases, including CMML, AML transformed from CMML, other types of AML, MDS, and MPN. RUNX1, ASXL1, and CBL, were commonly mutated and associated with lower OS compared to patients with only SRSF2 and TET2 mutations. When comparing OS for patients diagnosed with low-grade diseases (CMML or MDS), ASXL1 mutation was associated with an increased risk of death. No difference in OS was found between CMML vs MDS, or AML-CMML vs AML-Others when co-mutation with ASXL1, RUNX1, CUX1, JAK2, or CBL was present.