Myeloid/lymphoid neoplasms with eosinophilia: clinical picture and therapeutic approaches

Abstract

Myeloid/lymphoid neoplasms with eosinophilia (M/Leo) and tyrosine kinase (TK) fusion genes constitute a separate category within the 2016 World Health Organization (WHO) classification. All these are characterized by blood or tissue eosinophilia and the presence of a unique genetic abnormality. M/Leo may have diverse clinical manifestations with variable response to TK inhibitors (TKI). PDGFRA -rearranged neoplasms (usually with detectable FIP1L1-PDGFRA ) are found to be extremely sensitive to low dose of imatinib (IM at 100 mg daily) with nearly 100% hematological complete response rate. Moreover, >90% of IM treated patients may achieve long-term molecular response. IM discontinuation may result in sustained remission in c.50–60% of patients. An excellent response to IM (but at 400 mg/day) was also demonstrated for patients with PDGFRB rearrangements, but trials on IM cessation were not attempted. The FGFR1 -rearranged neoplasms are associated with an aggressive disease course and allogeneic stem cell transplantation (allo-SCT) is the only potentially curative approach. Participation in clinical trials should be recommended. Recently, pemigatinib was found to be effective in a proportion of FGFR1 -rearranged individuals. An aggressive outcome with rapid blast transformation is also characteristic for the JAK2 -rearranged neoplasms. These patients should be included in clinical trials or attempted with ruxolitinib or fedratinib as a ‘bridge’ to allo-SCT. A new category of neoplasms with eosinophilia and FLT3 and ABL1 rearrangements has not yet been incorporated into the WHO 2016 classification. The prognosis is poor with a tendency to evolve into resistant acute leukemia. The treatment includes TKI with known activity against FLT3/ABL1 followed by allo-SCT.