Risk Factors for Disease Progression in del(5q) MDS Patients Treated with Lenalidomide.

Introduction: Lenalidomide is a novel immunomodulatory drug that is highly effective in patients with transfusion-dependent MDS with del(5q.31) chromosomal abnormality. In the recent MDS-003 study of lenalidomide, there was a 76% erythroid response rate, including 67% transfusion independence. Cytogenetic complexity or bone marrow blast percentage did not affect this response rate. A number of patients experienced disease progression to higher FAB subtypes or AML. We questioned whether lenalidomide might promote disease progression in del(5q) MDS and performed a retrospective analysis to identify risk profiles.

Methods: Fifty patients from three institutions were included in this analysis. They were partly treated within the Lenalidomide-MDS003-study. Patients were treated with an initial lenalidomide dose of 10 mg po daily. In case of grade >2 neutropenia, G-CSF and antibiotics were administered.

Results: The median age was 71 years; 31 patients were female and 20 were male. Disease progression to a higher FAB subtype or to AML occurred in 13 patients (29.5%). 7 of the 13 patients had RAEB at the first lenalidomide dose. In addition, 3 of these had additional chromosomal aberrations (2, trisomy 21; 1, complex karyotype). Of the remaining 6 patients, 2 had a complex karyotype at the first lenalidomide dose, 1 had an additional inv(9)(p11q12), and 1 had hypocellular bone marrow so no FAB subtype could be assigned. Only 2 of 50 patients (4.3%) with 5q-syndrome progressed to AML; both patients developed acute erythroid leukemia (FAB M6).

Conclusion: Within the del(5q) MDS subgroup, patients with an isolated del(5q) chromosomal aberration and a bone marrow blast count of <5% have the longest overall survival. Patients with additional chromosomal abnormalities or a higher blast percentage have a much shorter overall survival and a higher risk for progressing to AML. Our data show that progression to higher MDS subtypes or AML occurs almost exclusively in patients with additional risk factors such as >5% bone marrow blasts or additional chromosomal anomalies. Lenalidomide does not seem to increase the risk of transition of del(5q) MDS to higher stages of disease.