Patients with myeloid malignancies bearing PDGFRB fusion genes achieve durable long-term remissions with imatinib.

Myeloid neoplasms and eosinophilia with rearrangements of PDGFRB are uncommon Philadelphia-negative myeloproliferative neoplasms. Patients are typically male, with morphologic features of a Philadelphia-negative chronic myeloproliferative syndrome or chronic myelomonocytic leukemia with eosinophilia. Reciprocal translocations involving PDGFRB result in fusion genes with constitutively activated receptor tyrosine kinase sensitive to inhibition with imatinib. We present an updated and expanded analysis of a cohort of 26 such patients treated with imatinib. After a median follow-up of 10.2 years (range, 1.8-17 years), the 10-year overall survival rate was 90% (95% confidence interval, 64%-97%); after median imatinib duration of 6.6 years (range, 0.1-12 years), the 6-year progression-free survival rate was 88% (95% confidence interval, 65%-96%). Of the patients, 96% responded; no patients who achieved a complete cytogenetic (n = 13) or molecular (n = 8) remission lost their response or progressed to blast crisis. Imatinib is well-tolerated and achieves excellent long-term responses in patients with PDGFRB rearrangements.