Long-Term Disease-Free Survival of Patients with AML Relapse After T-Cell-Depleted Allogeneic Stem Cell Transplantation by Re-Induction Therapy and Subsequent Interferon-Boosted Donor Lymphocyte Infusion
Authors: Eefting M. , Halkes C.J.M. , Kersting S. , Marijt W.A.F. , von dem Borne P.A. , Veelken J.H. , Falkenburg J.H.F. 
Published: October 2019

Abstract
Abstract 3064
Relapse of AML after allogeneic stem cell transplantation (alloSCT) has a very poor prognosis. Salvage re-induction chemotherapy leads to clinical remissions in a substantial number of patients, but these remissions tend to be of short duration. In contrast, donor lymphocyte infusions (DLI) have the potential to effect long-lasting remissions, but the interval of several weeks to months that is required to develop a DLI-induced anti-leukemia response may prevent efficient control of a highly proliferative leukemia. In addition, a high tumor burden may suppress the immune response. In contrast, the combination of efficient cytoreduction by chemotherapy with DLI administered in rapid succession under circumstances favoring the development of an early and profound immune response might have the potential to eradicate otherwise resistant leukemia cells. We therefore adopted an institutional therapeutic strategy for relapsed myeloid leukemia post-allogeneic SCT based on administration of DLI at the anticipated end of the neutropenic phase after salvage re-induction chemotherapy. At this time point, the high prevalence of a pro-inflammatory milieu should favor the induction of the immune response, and an expected state of lymphopenia should promote the expansion of infused T cells by homeostatic proliferation. If 3 weeks after DLI no graft versus host disease (GvHD) was observed, the potential anti-leukemia immune response was further amplified by treatment with interferon- α (IFN- α) until GvHD occurred.
Between January 2000 and December 2009 44 patients with relapsed myeloid malignancy after alloSCT were treated at our hospital. Pre-transplant diagnoses were AML n=40, CMML n=1 and MDS n=3. Median time from SCT to relapse was 187 days. Median follow-up after relapse was 3.1 years. 5 patients had a smouldering relapse (<10% bone marrow blasts) and 39 patients had an overt relapse.
Of 39 patients with overt relapse, 7 patients (18%) did not receive re-induction therapy due to poor performance status (n=5) or patient choice (n=2). 32 patients received remission-induction therapy consisting of gemtuzumab ozogamycin (n=9), cytosine arabinoside-containing chemotherapy (n=17), or both (n=6). Following this treatment, 7 of 32 patients had rapidly progressive disease during induction therapy (n=6) or died due to toxicity (n=1) and did not receive DLI.
The remaining 25 patients received DLI at a dose of 5.0×10 ^6 CD3+ cells/kg for related and 2.5×10 ^6 CD3+ cells/kg for unrelated donors 3 weeks after the start of remission-induction therapy. In 16 of these patients DLI was boosted with IFN- α 3.0×10 ^6 IE once daily. This strategy resulted in acute GvHD in 17 of 25 patients (n=8 grade 1–2, n=9 grade 3–4). At 6 weeks after DLI, 16 patients had reached CR, 5 patients had failed to reach CR (2 with GvHD) and 4 suffered treatment-related mortality (3 with GvHD). Of the 16 patients in CR, 4 had no signs of GvHD and developed a second relapse during the follow-up period. Only 3 of 12 patients in CR with signs of acute GvHD at 6 weeks after DLI developed a second relapse. In total, 9 of 17 patients (53%) with acute GvHD after DLI had long term survival versus none without acute GvHD. During follow-up, 8 patients developed chronic GvHD (n=4 limited, n=4 extensive).
Finally, 5 patients with an early detected smouldering relapse received DLI, which was boosted with IFN- α in 2 patients, without salvage re-induction therapy. All 5 patients developed GvHD (n=2 grade 1–2, n=3 grade 3–4) and 3 patients achieved a CR of whom 1 patient died from GvHD.
Our results indicate that treatment of relapsed AML after alloSCT with salvage re-induction therapy followed by DLI at the end of the neutropenic phase during minimal residual disease, with additional boosting of the immune response with IFN- α, can result in long-term disease-free survival.

Disclosures:
Off Label Use: Interferon: DLI-boosting.