LAUSR

Next-generation sequencing (NGS) has revolutionized the diagnostic, prognostic and treatment paradigms in myeloid malignancies. Although somatic mutations can be identified in the majority of patients with myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML), the mutational spectrum and prognostic significance of individual mutations is dependent on disease subtype and remains incompletely understood. In CMML, mutations in the addition of sex combs-like 1 (ASXL1) gene are the only mutations consistently associated with inferior survival in multivariable analysis and as such refine discrimination of clinical prognostic models. Nonetheless, these studies also suggest that the type of mutation may have prognostic significance as ASXL1 missense mutations are not similarly predictive of clinical outcomes. Additional studies have confirmed the prognostic significance of ASXL1 mutations in CMML while also identifying mutations of CBL, RUNX1, NRAS, and SETBP1 to have prognostic relevance. In MDS, mutations involving TP53, EZH2, ETV6, RUNX1, and ASXL1 genes are associated with inferior survival, albeit ASXL1 mutations are of only borderline significance. Importantly, the prognostic relevance of type of ASXL1 mutation has not been analyzed in MDS patients. These data suggest that there are distinct disease-specific implications in MDS versus CMML that apply to a similar mutational spectrum. Given the predicted differences in prognostic significance of ASXL1 between MDS and CMML, we sought to compare the impact of ASXL1 mutations in a combined cohort comprised of both diseases. We identified that although ASXL1 mutation was predictive for outcome in CMML (HR 2.97, 95% CI 1.21–7.06; P= 0.02), it had no impact on outcome in MDS patients (HR 1.04, P= 0.87). In addition, whereas the negative significance of ASXL1 mutation status was dependent on frameshift (FS) mutations (HR 3.85, 95% CI 1.84–15.61, P= 0.0026) in CMML, the type of mutation had no impact on MDS prognosis even when accounting for missense mutations. Patients were identified retrospectively from the Moffitt Cancer Center (MCC) database that had NGS performed and a diagnosis of CMML or MDS according to WHO criteria (including patients with refractory anemia with excess blasts in transformation according to FAB). Pathology review was performed at MCC. This study was approved by the MCC Scientific Review Committee and institutional review board. From May 2013 to July 2015, a total of 60 CMML patients were identified who underwent NGS who were compared to a cohort of 195 MDS patients (Table 1). From May 2013 to October 2014, targeted amplicon based NGS of 21 myeloid genes was performed on DNA extracted from mononuclear cells of BM aspirate or peripheral blood as previously described, which was followed by NGS using a 32 gene panel. The lower limit of detection for variant calling was set at a 5% variant allele frequency (VAF) and the minimum depth of coverage was 500×. Clinical characteristics were cataloged from the date of mutation analysis. Kaplan–Meier estimates were used to estimate OS and analyzed from the date of mutation identification. Cox regression models were cr7eated to adjust for clinical characteristics. Categorical and continuous variables were compared by Fisher’s exact test and Mann–Whitney’s test, respectively.