Allogeneic stem cell transplantation for myeloproliferative neoplasm in blast phase

The prognosis for patients with Philadelphia-negative myeloproliferative neoplasms (MPN) who evolve into acute myeloid leukemia (AML) or blast phase (MPN-BP) is extremely poor. Although allogeneic stem cell transplantation (allo-SCT) is considered potentially curative, very few patients have been reported who have undergone allo-SCT for MPN-BP; therefore the success rate remains unknown. In a retrospective review, we identified 13 patients with an MPN transformation to blast phase after a median 9 years (range 5 months to 30 years); 8 (median age 55) continued to allo-SCT within 6 months. Induction chemotherapy cleared blood/marrow blasts in 60% (6/10) (2 declined therapy, 1 had early death). At the time of allo-SCT, 5/8 patients were in complete remission (CR) of their leukemia or had returned to MPN chronic phase (CP), 2 had residual blood blasts and 1 was refractory with >5% marrow blasts. At follow-up (median 20.3 months), 6 patients are alive in CR of both their leukemia/MPN. All 5 patients in CR/CP at pre-allo-SCT remain alive in remission, while 2/3 with persistent blood/marrow blasts relapsed and expired. We conclude that MPN-BP can be cured by allo-SCT in a significant percentage of patients, but that adequate leukemic clearance prior to allo-SCT offers an optimal outcome.