Outcomes of Patients with Myelofibrosis and Favorable Karyotype

Introduction

Myelofibrosis (MF) is an aggressive myeloproliferative neoplasm negatively affecting patient’s (pts) overall survival (OS). Several clinical and molecular factors, such as anemia, leukocytosis, thrombocytopenia, increased blasts, presence of unfavorable karyotype, or adverse molecular abnormalities (e.g., ASXL1, IDH1/2, SRSF2, EZH2), further worsen outcomes. Pts with favorable karyotype (e.g., diploid, single deletion 13q, or single deletion 20q), are assumed to have comparable and superior outcome, only affected by their clinical features and molecular background. We decided to evaluate how adverse clinical and molecular factors impact OS within this subset of patients.

Methods

We conducted a retrospective analysis on patients with favorable karyotype and newly diagnosed MF who presented to our institution within the last 20 years. Favorable karyotype was considered according to classification in DIPSS-Plus and MIPSS70v2.0 models. Prognostic models, IPSS, DIPSS, DIPSS-Plus and MIPSS70v.20 were calculated for patients as published. Molecular analysis was performed in some patients using at least 28-gene panel by next generation sequencing (NGS). Categorical variables were compared by Chi-squared test. Univariate analysis for association between variables and outcome was performed with Cox-regression analysis. Overall survival (OS) was estimated using Kaplan-Meier method and calculated from the time of presentation to our institution until the last follow-up or death.

Results

Among 1002 patients, 741 pts (74%) had diploid karyotype (DP); the remaining patients had single deletion 13q (del13q, n 33), single deletion 20q (n 97), single abnormality of chromosome 1, 9 or minus Y (n 131). Only pts with del13q had inferior OS to all other groups (42 vs ~ 62 months, p 0.001), and therefore we decided to further focus on pts with del13q and DP karyotype. Patients and disease characteristics are detailed in Tables 1 and 2. We did not observe any significant clinical differences between groups. Distribution by prognostic systems; IPSS, DIPSS, DIPSS-Plus and MIPSS10v2.0 is shown in Table 1. IPSS and DIPSS classified more patients with del13q into higher (combined intermediate 2 and high) risks. DIPSS-Plus and MIPSS70v2.0 showed similar distribution of patients into risks in both groups. Forty – two percent (n 87) and 36% (n 4) of patients with DP karyotype and del13q carried at least one high risk molecular mutation (HMR; such as ASXL1, IDH1/2, EZH2, U2AF1/SRSF2/SF3B1), respectively (Table 2).

Whilst all applied clinical risk models (IPSS, DIPSS, DIPSS-Plus) appropriately discriminated distinct OS in pts with DP karyotype, only DIPSS-Plus was able to accurately predict distinct OS in those with del13q (Table 3). MIPSS70v2.0 (only patients with NGS panel) did not predict for distinct OS in DP or del13q pts (Table 3).

Pts with DP karyotype had superior OS to those with del13q with median OS of 62 and 42 months, respectively (Figure 1), p < 0.001, HR 0.49, 95% CI 0.32-0.78. Although presence of HMR had negative impact on OS in both groups (Figure 2), pts with del13q with HRM had OS of only 15 months (vs 55 months in DP pts with HMR, p < 0.001).

Conclusion

Patients with MF and del13q appear to have inferior OS than those with diploid karyotype, despite similar clinical features. Impact of molecular abnormalities, especially presence of high-risk mutations, might be underestimated in this group and deserves further investigation. Ongoing research in our center is aimed to provide new evidence on the role of mutations for this karyotypically “favorable” subgroup.