Is Imatinib Maintenance Required for Patients with Relapse Chronic Myeloid Leukemia Post-Transplantation Obtaining CMR? A Pilot Retrospective Investigation

Improving outcomes in chronic myeloid leukemia through harnessing the immunological landscape

The quest for treatment-free remission (TFR) and deep molecular response (DMR) in chronic myeloid leukemia (CML) has been profoundly impacted by tyrosine kinase inhibitors (TKIs). Immunologic surveillance of residual leukemic cells is hypothesized to be one of the critical factors in successful TFR, with self-renewing leukemic stem cells implicated in relapse. Immunological characterization in CML may help to develop novel immunotherapies that specifically target residual leukemic cells upon TKI discontinuation to improve TFR rates. This review focuses on immune dysfunction in newly diagnosed CML patients, and the role that TKIs and other therapies have in restoring immune surveillance. Immune dysfunction and immunosurveillance in CML points towards several emerging areas in the key goals of DMR and TFR, including: (1) Aspects of innate immune system, in particular natural killer cells and the newly emerging target plasmacytoid dendritic cells. (2) The adaptive immune system, with promise shown in regard to leukemia-associated antigen vaccine-induced CD8 cytotoxic T-cells (CTL) responses, increased CTL expansion, and immune checkpoint inhibitors. (3) Immune suppressive myeloid-derived suppressor cells and T regulatory cells that are reduced in DMR and TFR. (4) Immunomodulator mesenchymal stromal cells that critically contribute to leukomogenesis through immunosuppressive properties and TKI- resistance. Therapeutic strategies that leverage existing immunological approaches include donor lymphocyte infusions, that continue to be used, often in combination with TKIs, in patients relapsing following allogeneic stem cell transplant. Furthermore, previous standards-of-care, including interferon-α, hold promise in attaining TFR in the post-TKI era. A deeper understanding of the immunological landscape in CML is therefore vital for both the development of novel and the repurposing of older therapies to improve TFR outcomes.

Ponatinib therapy in recurrent Philadelphia chromosome-positive central nervous system leukemia with T315I mutation after Allo-HSCT

Central nervous system leukemia (CNSL) relapse is relatively common among Philadelphia chromosome-positive (Ph+) leukemia patients who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). The prognosis of patients is dismal for those with a BCR-ABL T315I mutation, which is resistant to TKIs including second-generation drugs. We assessed ponatinib for nine patients with recurrent Ph+ CNSL and a T315I mutation after allo-HSCT, including five patients with Ph+ acute lymphoblastic leukemia and four with chronic myelogenous leukemia. Five patients experienced isolated CNSL relapse, and four experienced CNSL with hematologic relapse. All patients received ponatinib combined with intrathecal chemotherapy, and four patients with hematologic relapse received systemic chemotherapy and/or donor lymphocyte infusion. All patients achieved a deep molecular response and central nervous system remission (CNSR) at a median time of 1.5 (range: 0.7-3) months after ponatinib treatment. Two patients experienced a second CNSL relapse due to ponatinib reduction, but they achieved CNSR again after an increase to the standard dosage. Six patients developed graft versus host disease. By April 1, 2019, eight patients were alive, and one died of pneumonia. The median time of survival after the first CNSL relapse posttransplantation was 18 (range: 11.2-48.5) months. Our data from a small number of samples suggests that ponatinib is effective for recurrent Ph+ CNSL patients with a BCR-ABL T315I mutation after allo-HSCT and warrants broader clinical evaluation.

Chronic Myeloid Leukemia Relapsing 25 Years after Allogenic Stem Cell Transplantation

Chronic myeloid leukemia (CML) is a myeloproliferative disorder in which neoplastic cells exhibit the Philadelphia chromosome and the related oncoprotein BCR-ABL1. Allogeneic stem cell transplantation (allo-SCT) was considered the first-line treatment for CML, before the introduction of tyrosine kinase inhibitors (TKIs). However, patients are at risk for relapse years after transplantation. We present a patient who relapsed 25 years after allo-SCT for chronic phase CML. Polymerase chain reaction (PCR) detected gradually evaluated levels of BCR-ABL1 transcripts, eventually leading to the diagnosis of relapsed disease. Additional mutational analyses did not reveal mutations in the BCR-ABL1 gene, or other cooperating mutations. The patient was successfully treated with imatinib 400 mg daily, leading to new molecular remission. The case presentation emphasizes the need for long-term follow-up of such patients and the potential benefit of initiating TKI treatment with early signs of relapse.

Donor Lymphocyte Infusions for Chronic Myeloid Leukemia Relapsing after Allogeneic Stem Cell Transplantation: May We Predict Graft-versus-Leukemia Without Graft-versus-Host Disease?

Donor lymphocyte infusions (DLI) are an effective treatment for relapsed chronic myeloid leukemia (CML) after allogeneic stem cell transplantation (alloSCT). Leukemia resistance and secondary graft-versus-host disease (GVHD) are major obstacles to success with DLI. The aim of this study was to identify pre-DLI factors associated with prolonged survival in remission without secondary GVHD. We retrospectively analyzed 500 patients treated with DLI for CML relapse (16% molecular, 30% cytogenetic, and 54% hematological) after alloSCT. The overall probabilities of failure- and secondary GVHD-free survival (FGFS) were 29% and 27% at 5 and 10 years after DLI, respectively. The type of relapse was the major factor influencing FGFS (40% for molecular and/or cytogenetic relapse and 20% for hematological relapse at 5 years, P < .001). Chronic GVHD before DLI and an interval <1 year between alloSCT and first DLI were independently associated with inferior FGFS in patients with molecular and/or cytogenetic relapse. Consequently, FGFS was 13%, 35%, to 56% at 5 years in patients with 2, 1, and 0 adverse features, respectively. In patients with hematological relapse, independent adverse prognostic factors for FGFS were initial dose of CD3(+) cells ≥ 50 × 10(6)/kg, donor-recipient sex mismatch, and chronic GVHD before DLI. FGFS was 0%, 17%, 33%, to 37% in patients with 3, 2, 1, and 0 adverse features, respectively. The probability of survival in remission without secondary GVHD was highest (>50% at 5 years) when DLI were given beyond 1 year from alloSCT for molecular and/or cytogenetic CML relapse that was not preceded by chronic GVHD.