Disease Overview
Treatment Overview
Current Clinical Trials

Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)

Chronic eosinophilic leukemia (CEL) is a chronic myeloproliferative disorder of unknown etiology in which a clonal proliferation of eosinophilic precursors results in persistently increased numbers of eosinophils in the blood, bone marrow, and peripheral tissues. In CEL, the eosinophil count is greater than or equal to 1.5 × 10⁹/L in the blood.[1] To make a diagnosis of CEL, there should be evidence for clonality of the eosinophils or an increase in blasts in the blood or bone marrow. In many cases, however, it is impossible to prove clonality of the eosinophils, in which case, if there is no increase in blast cells, the diagnosis of idiopathic hypereosinophilic syndrome (HES) is preferred. Because of the difficulty in distinguishing CEL from HES, the true incidence of these diseases is unknown, though they are rare. In about 10% of patients, eosinophilia is detected incidentally. In others, constitutional symptoms, such as fever, fatigue, cough, angioedema, muscle pains, pruritus, and diarrhea are found.[1,2] No single or specific cytogenetic or molecular genetic abnormality has been identified in CEL.

The optimal treatment of CEL remains uncertain, partially on account of the rare incidence of this chronic myeloproliferative disorder and the variable clinical course, which can range from cases with decades of stable disease to cases with rapid progression to acute leukemia. Case reports suggest that treatment options include bone marrow transplantation and interferon-alpha.[3,4] Treatment of HES has included corticosteroids; chemotherapeutic agents such as hydroxyurea, cyclophosphamide, and vincristine; and interferon-alpha.[5,6] Case reports suggest symptomatic responses to imatinib mesylate for patients with HES who have not responded to conventional options.[6-8][Level of evidence: 3iiiDiv] Imatinib mesylate acts as an inhibitor of a novel fusion tyrosine kinase, FIP1L1-PDGFR alpha fusion tyrosine kinase, which results as a consequence of interstitial chromosomal deletion.[6,9][Level of evidence: 3iiiDiv] HES with the FIP1L1-PDGFR alpha fusion tyrosine kinase translocation has been shown to respond to low-dose imatinib mesylate.[9]

Check for U.S. clinical trials from NCI's PDQ Cancer Clinical Trials Registry that are now accepting patients with chronic eosinophilic leukemia. The list of clinical trials can be further narrowed by location, drug, intervention, and other criteria.

General information about clinical trials is also available from the NCI Web site.

References

1. Bain B, Pierre P, Imbert M, et al.: Chronic eosinophillic leukaemia and the hypereosinophillic syndrome. In: Jaffe ES, Harris NL, Stein H, et al., eds.: Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France: IARC Press, 2001. World Health Organization Classification of Tumours, 3, pp 29-31. 
   
   
2. Weller PF, Bubley GJ: The idiopathic hypereosinophilic syndrome. Blood 83 (10): 2759-79, 1994.  [PUBMED Abstract]
   
   
3. Basara N, Markova J, Schmetzer B, et al.: Chronic eosinophilic leukemia: successful treatment with an unrelated bone marrow transplantation. Leuk Lymphoma 32 (1-2): 189-93, 1998.  [PUBMED Abstract]
   
   
4. Yamada O, Kitahara K, Imamura K, et al.: Clinical and cytogenetic remission induced by interferon-alpha in a patient with chronic eosinophilic leukemia associated with a unique t(3;9;5) translocation. Am J Hematol 58 (2): 137-41, 1998.  [PUBMED Abstract]
   
   
5. Butterfield JH, Gleich GJ: Interferon-alpha treatment of six patients with the idiopathic hypereosinophilic syndrome. Ann Intern Med 121 (9): 648-53, 1994.  [PUBMED Abstract]
   
   
6. Gotlib J, Cools J, Malone JM 3rd, et al.: The FIP1L1-PDGFRalpha fusion tyrosine kinase in hypereosinophilic syndrome and chronic eosinophilic leukemia: implications for diagnosis, classification, and management. Blood 103 (8): 2879-91, 2004.  [PUBMED Abstract]
   
   
7. Gleich GJ, Leiferman KM, Pardanani A, et al.: Treatment of hypereosinophilic syndrome with imatinib mesilate. Lancet 359 (9317): 1577-8, 2002.  [PUBMED Abstract]
   
   
8. Ault P, Cortes J, Koller C, et al.: Response of idiopathic hypereosinophilic syndrome to treatment with imatinib mesylate. Leuk Res 26 (9): 881-4, 2002.  [PUBMED Abstract]
   
   
9. Cools J, DeAngelo DJ, Gotlib J, et al.: A tyrosine kinase created by fusion of the PDGFRA and FIP1L1 genes as a therapeutic target of imatinib in idiopathic hypereosinophilic syndrome. N Engl J Med 348 (13): 1201-14, 2003.  [PUBMED Abstract]
   
   

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