FIP1L1-PDGFRA molecular analysis in the differential diagnosis of eosinophilia

<p>Abstract</p> <p>Background</p> <p>Primary eosinophlia associated with the <it>FIP1L1-PDGFRA </it>rearrangement represents a subset of chronic eosinophilic leukaemia (CEL) and affected patients are very sensitive to imatinib treatment. This study was undertaken in order to examine the prevalence and the associated clinicopathologic and genetic features of <it>FIP1L1-PDGFRA </it>rearrangement in a cohort of 15 adult patients presenting with profound eosinophilia (> 1.5 × 10⁹/L).</p> <p>Methods</p> <p>Reverse transcriptase-polymerase chain reaction (RT-PCR) was used for the detection of <it>FIP1L1-PDGFRA </it>rearrangement and the results confirmed by direct sequencing. <it>C-KIT</it>-D816V mutation was analysed retrospectively by PCR and restriction-fragment-length-polymorphism (PCR-RFLP), in all cases with primary eosinophilia.</p> <p>Results</p> <p>Two male patients with splenomegaly carried the <it>FIP1L1-PDGFRA </it>rearrangement, whilst 2 others were ultimately classified as suffering from idiopathic hypereosinophlic syndrome (HES) and one from systemic mastocytosis. These patients were negative for the <it>C-KIT</it>-D816V mutation and received imatinib (100–400 mg daily). Patients with CEL and HES responded to imatinib and remained in complete haematological, clinical and molecular (for carriers of <it>FIP1L1-PDGFRA </it>rearrangement) remission for a median of 28.2 months (range: 11–54), whilst the patient with systemic mastocytosis did not respond. Interestingly, in both patients with <it>FIP1L1-PDGFRA </it>rearrangement, the breakpoints into <it>PDGFRA </it>were located within exon 12 and fused with exons 8 and 8a of <it>FIP1L1</it>, respectively.</p> <p>Conclusion</p> <p>An early diagnosis of <it>FIPIL1-PDGFRA</it>-positive CEL and imatinib treatment offer to the affected patients an excellent clinical therapeutic result, avoiding undesirable morbidity. Moreover, although the molecular mechanisms underlying disease pathogenesis remain to be determined, imatinib can be effective in patients with idiopathic HES.</p

Safety and efficacy of imatinib in chronic eosinophilic leukaemia and hyperosinophilic syndrome - a phase-II study

This study evaluated the efficacy and safety of imatinib in chronic eosinophilic leukaemia (CEL, n = 23) and hypereosinophilic syndrome (HES, n = 13). In CEL with FIP1L1-PDGFRA (n = 16) or various PDGFRB fusion genes (n = 5), complete haematological remission (CHR) was achieved in 95% (20/21) after 3 months. Complete molecular remission (CMR) was seen in 75% (12/16) of cases with FIP1L1-PDGFRA positive CEL by 6 months, and in 87% (13/15) after 12 months. CMR was achieved in three of five PDGFRB fusion positive patients after 3, 9 and 18 months respectively. All patients are currently on imatinib (100 mg; n = 13, 400 mg; n = 8) and no molecular relapse has yet been observed (median 26·7 months; range, 6·9–39·9). Imatinib was less effective in HES and CEL without known molecular aberration (n = 15); CHR was observed in 40% (6/15) of patients, two patients relapsed after 4·8 and 24·5 months. Three patients died due to imatinib-resistant progressive CEL (n = 2) or myocardial infarction (n = 1) unrelated to study treatment. Overall, imatinib was well tolerated with a low incidence of grade III/IV toxicities. These data confirmed the long-term efficacy of imatinib for PDGFR-rearranged CEL patients, and also showed that a minority of HES cases without known molecular aberrations may benefit from imatinib