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CD123 is the α-subunit of the interleukin-3 receptor; it represents a potential therapeutic target in systemic mastocytosis (SM) given its absent expression on normal/reactive mast cells (MCs) and aberrant expression on neoplastic MCs. We studied 58 SM patients to define CD123 expression patterns by immunohistochemistry and its clinical significance. Two hematopathologists independently scored bone marrow slides using predefined histologic parameters. In all, 23 patients had indolent SM (ISM), 10 aggressive SM (ASM), 23 SM with associated hematological neoplasm (SM-AHN) and 2 had mast cell leukemia (MCL). MC_CD123 expression was demonstrable in 37 (64%) cases; expression rates were 100%, 61%, 57% and 0% in ASM, ISM, SM-AHN and MCL, respectively (P=0.02). Focal proliferation of plasmacytoid dendritic cells (PDCs) around MC aggregates, suggesting a tumor-promoting role for PDCs, was noted in 44 (76%) cases, and was significantly higher in CD123-positive versus -negative cases (87% versus 50%, P=0.005). CD123 expression and its staining intensity had prognostic value in SM-chronic myelomonocytic leukemia and nonindolent SM patients, respectively. These observations suggest that targeting CD123 in SM may have direct (via MCs) and indirect (via PDCs) antitumor effects and clinical trials to that effect require laboratory correlative studies to address the observed target expression heterogeneity.

Among 274 patients with chronic myelomonocytic leukemia (CMML) and followed for a median of 17.1 months, blast transformation (BT) occurred in 36 (13%). On multivariable analysis, risk factors for BT were presence of circulating blasts (HR 5.7; 95% CI 2.8-11.9) and female gender (HR 2.6; 95% CI 1.3-5.1); the results remained unchanged when analysis was restricted to CMML-1. ASXL1/SRSF2/SF3B1/U2AF1/SETBP1 mutational frequencies were not significantly different between time of CMML diagnosis and BT. Median survival post-BT was 4.7 months (5-year survival 6%) and better with allogeneic stem cell transplant (SCT) (14.3 months vs. 4.3 months for chemotherapy vs. 0.9 months for supportive care; P = 0.03). Neither karyotype nor mutational status was independently associated with risk of BT or post-BT survival. We conclude that female patients with CMML and those with circulating blasts are at a higher risk of BT. Post-BT survival is dismal and our observations suggest consideration of allogeneic SCT prior to BT., (© 2015 Wiley Periodicals, Inc.)

In patients with chronic myelomonocytic leukemia (CMML), age>65 years is an adverse prognostic factor. Our objective in the current study was to examine risk factors for survival and treatment outcome in 261 'young' adults with CMML, as defined by age ⩽65 years. In multivariable analysis, lower HB (P=0.01), higher circulating blast % (P=0.002), ASXL1 (P=0.0007) and SRSF2 mutations (P=0.008) and Mayo-French cytogenetic stratification (P=0.04) negatively impacted survival. Similarly, leukemia-free survival was independently affected by higher circulating blast % (P<0.0001), higher bone marrow blast % (P=0.0007) and the presence of circulating immature myeloid cells (P=0.0002). Seventy-five (29%) patients received hypomethylating agents (HMA), with the median number of cycles being 5, and the median duration of therapy being 5 months. The over-all response rate was 40% for azacitidine and 30% for decitabine. Fifty-three (24%) patients underwent an allogeneic hematopoietic stem cell transplant (AHSCT), with a response rate of 56% and a non-relapse mortality of 19%. Survival in young adults with CMML, although higher than in older patients, is poor and even worse in the presence of ASXL1 and SRSF2 mutations. Treatment outcome was more impressive with AHSCT than with HMA and neither was influenced by ASXL1/SRSF2 mutations or karyotype.

Background: Vascular events in essential thrombocythemia (ET) are associated with advanced age and thrombosis history. Recent information suggests additional effect from the presence of specific mutations., Objectives: To examine the influence of age and thrombosis history on the reported association between mutational status and thrombosis-free survival in ET., Patients and Methods: Analysis was performed using a Mayo Clinic cohort of 300 ET patients, and key findings were reanalyzed by including additional 102 Italian patients., Results: Among 300 Mayo patients with ET (median age 55 yr, 60% females), mutational frequencies were 53% JAK2, 32% CALR, 3% MPL, and 12% JAK2, CALR and MPL wild type. One hundred and six (35%) patients experienced arterial (n = 75) or venous (n = 43) events, before (n = 55) or after (n = 71) diagnosis. In univariate analysis, compared to JAK2-mutated cases, JAK2, CALR and MPL wild type (HR 0.31, 95% CI 0.11-0.86), and CALR-mutated (0.53, 95% CI 0.30-0.92) patients displayed better thrombosis-free survival. JAK2, CALR, and MPL wild type remained significant (P = 0.03; HR 0.32, 95% CI 0.11-0.9) during multivariable analysis that included age (P = 0.01) and thrombosis history (P = 0.0006); a favorable impact from CALR mutations was of borderline significance (P = 0.1; HR 0.62, 95% CI 0.35-1.1), but became significant (P = 0.02) when multivariable analysis including thrombosis history (P = 0.02) was performed on patients younger than 60 yr of age., Conclusions: The favorable impact of mutational status on thrombosis-free survival in ET might be most evident for JAK2, CALR, and MPL wild type patients, whereas the favorable effect from CALR mutations might be confined to young patients., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)