Leukemia-associated immunophenotypes subdivided in "categories of specificity" improve the sensitivity of minimal residual disease in predicting relapse in acute myeloid leukemia.

BACKGROUND: The assessment of minimal residual disease (MRD) by flow cytometry (FC) has a prognostic impact in acute myeloid leukemia (AML), despite the low sensitivity in predicting relapse. Nonetheless, the role of leukemic-associated immunophenotypes (LAIPs)-related specificity on the sensitivity of MRD has not been clarified yet. In this respect, we accomplished this study. METHODS: LAIP-frequencies of bone marrow samples from healthy donors and patients after treatment were quantified and subdivided in "categories of specificity" named as: "strong," "good," and "weak." At the following, the diagnostic performance of MRD was investigated in terms of sensitivity, specificity, predictive values, likelihood ratio (LR). RESULTS: "Strong" LAIPs were identified by CD7, CD2, CD4, and CD56 markers while "weak" LAIPs, independently of coexpressed markers, were mainly observed in CD33+ cells. MRD identified patients with significantly low DFS and OS but showed a low sensitivity in predicting relapse. Interestingly, majority of recurrences was noticed in patients with two LAIPs and lacking of "strong" LAIPs or only with one "good" LAIP. Thus, only patients showing one "strong" or two "good" LAIPs were considered suitable for MRD monitoring and selected to be further investigated. In this subset, positive MRD predicted a poor prognosis. Moreover, a higher sensitivity, negative predictive value (NPV) and LR- were observed after comparison with the previous series. CONCLUSIONS: These data highlight the relevant role of LAIP classification in "categories of specificity" in improving the sensitivity of MRD as assessed by FC.

Two novel imatinib-responsive PDGFRA fusion genes in chronic eosinophilic leukaemia.

We identified two patients with a t(2;4)(p24;q12) and a t(4;12)(q2?3;p1?2), respectively, in association with BCR-ABL and FIP1L1-PDGFRA negative chronic eosinophilic leukaemia. Molecular analysis revealed a novel STRN-PDGFRA fusion for the t(2;4) and ETV6-PDGFRA for the t(4;12). The fusions were confirmed by specific amplification of the genomic breakpoints, reverse transcription polymerase chain reaction and fluorescence in situ hybridisation. Both patients were treated with imatinib and, following a rapid haematological response, achieved cytogenetic remission and a major molecular response. In conclusion, PDGFRA fuses to diverse partner genes in myeloid disorders. Identification of these fusions is important as they are particularly sensitive to imatinib.