Imatinib synergizes with donor lymphocyte infusions to achieve rapid molecular remission of CML relapsing after allogeneic stem cell transplantation.

Donor lymphocyte infusions (DLI) have been the mainstay of treatment for chronic myeloid leukemia (CML) relapsing after allogeneic stem cell transplantation (allo-SCT). Imatinib mesylate (IM) is also effective in these patients. However, advanced phase relapse (APRel) responds poorly with either treatment. To test the possibility that combinations of DLI and IM might be more effective, 37 patients with CML relapsing after allo-SCT between August 1994 and May 2004 were studied. Ten had molecular relapse (MRel), 14 hematological relapse (HRel) and 13 APRel. Thirteen received DLI, 9 IM and 11 DLI+IM. Four patients received DLI+IM but not concurrently. Thirty (81%) patients responded (actuarial survival and current leukemia-free survival of 80.6 +/- 6.7% and 69.1 +/- 7.7%). Of 30 patients, 26 are in molecular remission (MR), median follow-up of 1,226 days (range 249-3257) since relapse. Ten of 11 patients (including four with APRel) treated with DLI+IM achieved MR in 3 months and all are alive in MR. In contrast, only two of 22 treated with either modality (1/13 DLI and 1/9 IM) achieved MR at 3 months, 15 are alive, 11 in MR. Four patients receiving nonconcurrent DLI+IM are also alive in MR. In conclusion, DLI appears to synergize with IM to induce rapid and durable MR.