Hematopoietic Chimerism in Patients with Hematological Malignancies Treated with Donor Lymphocyte Infusions Combined with IL-2 for Relapse after Allogeneic Stem Cell Transplantation.

Donor lymphocyte infusions (DLI) are considered to be the treatment of choice in pts with relapses after allogeneic hematopoietic stem cell transplantation (HSCT). This kind of treatment is based on alloreactivity of donor lymphocytes, mediating a graft-versus-leukemia (GVL) effect. However, the relapses of acute leukemia in many cases are not susceptible to DLI. There were few reports that the concominant administration of cytokines (IL-2, IFN-alfa) and DLI is more efficient for conversion to complete donor chimerism (CC) from mixed chimerism (MC) and leads to remission in pts relapsed after HSCT, but the significance of this therapy is still not estimated. The aim of study was to evaluate the efficacy of DLI treatment combined with IL-2 i.v. administration for CC establishment and remission induction in pts with relapses after HSCT for hematological malignancies. 26 pts were treated with DLI for relapses after ASCT from related siblings in 2001–2007. 12 of them were included in the study. Median age was 25 y (16–44), 9 men/3 woman, 4 pts with AML, 1 - APL, 1 - ALL, 1 -ANL, 3 -CML, 2- MDS. 2 pt received reduced intensity HSCT, 10- conventional one. Median time to relapse was 12,5 months (3,5 – 48 months).10 pts demonstrated hematological relapses, 1 pt with APL and 1 pt with CML - molecular relapses. All pts with AL in overt relapse received chemotherapy first and then DLI was performed in aplasia. CML pts were treated with Hydrea and Glivec and then DLI were administrated. Median dose of infused DL was 6,34 x 10⁸/kg (median 6 transfusions per pt) with median of CD3+ cells. Chimerism status was investigated on BM and PB using VNTR/STR analysis at relapse, before every DLI and monthly after DLI completion. All pts demonstrated MC in bone marrow before chemotherapy (median 74% of host DNA). 9 pts were still MC after chemotherapy and before DLI (median 38% of host DNA), 3 pts became CC before DLI. In all pts DLI were combined with IL-2 (2–6 MU with every DLI). In 6 pts with MC after chemotherapy only 1 (with CML) became CC after 1 course of DLI and developed aGVHD II–III and then cGVHD. 5 pts (with AL and MDS) after DLI were still MC remaining in hematological remission. One of them died of CMV infection. 2 pts recieved the 2nd course of DLI + IL-2, became CC and are still well and alive (1 - with cGVHD, 1 - without GVHD) for 30 months. For 2 pts (AML) with MC 2nd DLI course was not possible (donor was not available) and they received the course of IL-2 (5 days for 6 MU daily) in 2 months after DLI. The both are in complete remission with CC and cGVHD. 4 pts showed no effect and soon relapsed despite the 2nd DLI course in 2 pt and 2nd course of IL-2 in 1 pt. Despite the small and heterogenious group we may conclude, that DLI administration concomitantly with IL-2 leads to more prominent GVL effect and quick conversion from MC to CC. The interesting observation is that the additional infusions of IL-2 were effective for conversion to CC and remission induction in 3 of 4 pts resistant for DLI.