Evidence-based guidelines for the use of tyrosine kinase inhibitors in adults with Philadelphia chromosome-positive or BCR-ABL-positive acute lymphoblastic leukemia: a Canadian consensus

The genomic and biological complexity of mixed phenotype acute leukemia

Mixed phenotype acute leukemia (MPAL) is a heterogeneous group of leukemias that are defined immunophenotypically by antigen expression on blasts of both myeloid and lymphoid lineage. With the exception of BCR-ABL positive and KMT2A rearranged MPAL, the biology of the majority of MPAL remains uncertain. Several recent studies have explored the genomic and epigenetic landscape of MPAL and have suggested a further refinement of the WHO classification to emphasize the genomic heterogeneity of MPAL. Further studies including single cell analysis, whole exome sequencing and time of flight cytometry will provide for further biological characterization. Treatment decisions are complicated due to this lack of classification and the dearth of prospective randomized studies. Acute lymphoblastic leukemia-type therapy appears to achieve higher remission rates, and allogenic stem cell transplantation may be beneficial in a select group of patients in first complete remission. Multi-center collaborations may answer these questions more conclusively. Our review aims to discuss the diagnostic challenges, recent genomic studies and therapeutic strategies in this poorly understood disease.

Curing Ph+ ALL: assessing the relative contributions of chemotherapy, TKIs, and allogeneic stem cell transplant

The understanding and treatment of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia have changed rapidly in the past 10 years. The outcome is equally as good as for Ph- disease, and with targeted tyrosine kinase inhibitor therapies in addition to chemotherapy, the novel immunotherapy approaches, and the extension of allogeneic hematopoietic stem cell transplant (allo-HCT) to older individuals, there is the potential to exceed this outcome. There is particular interest in reducing chemotherapy exposure and considering for whom allo-HCT can be avoided. However, the patient population that can help test these options in clinical trials is limited in number, and the available evidence is often derived from single-arm studies. This paper summarizes outcomes achieved with recent approaches to de novo Ph+ acute lymphoblastic leukemia in the postimatinib era and helps integrate all the available information to assist the reader to make informed choices for patients in an increasingly complex field.

The consensus on indications, conditioning regimen, and donor selection of allogeneic hematopoietic cell transplantation for hematological diseases in China-recommendations from the Chinese Society of Hematology

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is widely used to treat malignant hematological neoplasms and non-malignant hematological disorders. Approximately, 5000 allo-HSCT procedures are performed in China annually. Substantial progress has been made in haploidentical HSCT (HID-HSCT), pre-transplantation risk stratification, and donor selection in allo-HSCT, especially after the establishment of the "Beijing Protocol" HID-HSCT system. Transplant indications for selected subgroups in low-risk leukemia or severe aplastic anemia (SAA) differ from those in the Western world. These unique systems developed by Chinese doctors may inspire the refining of global clinical practice. We reviewed the efficacy of allo-HSCT practice from available Chinese studies on behalf of the HSCT workgroup of the Chinese Society of Hematology, Chinese Medical Association and compared these studies to the consensus or guideline outside China. We summarized the consensus on routine practices of all-HSCT in China and focused on the recommendations of indications, conditioning regimen, and donor selection.

The evolving role of chemotherapy and hematopoietic cell transplants in Ph-positive acute lymphoblastic leukemia in adults

The introduction of the tyrosine kinase inhibitors (TKI) into the treatment of patients with Ph or BCR-ABL1-positive acute lymphoblastic leukemia has revolutionized the treatment of this poor prognosis acute leukemia. The combination of TKI with chemotherapy has improved response rates and allowed more patients to proceed to allogeneic hematopoietic cell transplant (alloHCT). Older patients have excellent responses to TKI and corticosteroids or in combination with minimal chemotherapy. This raises the question as to whether patients require full-intensity chemotherapy with TKI to achieve molecular remissions. The pediatricians have proposed that cure is achievable without alloHCT in children. These results have suggested that many patients may not require traditional chemotherapy in addition to TKI to achieve remission, and that patients who achieve a negative minimal residual disease state may not require alloHCT. The data in support of these questions is presented here and a suggested future clinical trial design based on these data is proposed.

Hyper-CVAD Compared With BFM-like Chemotherapy for the Treatment of Adult Acute Lymphoblastic Leukemia. A Retrospective Single-Center Analysis

BACKGROUND

Several induction regimens have been developed for treatment of adult patients with acute lymphoblastic leukemia (ALL). However, only a few prospective randomized trials have directly compared these regimens.

PATIENTS AND METHODS

In this report, we retrospectively evaluated the outcome of 62 adult ALL patients treated with either hyper-CVAD (hyper fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone; n = 38) or a BFM (Berlin-Frankfurt-Munster)-like regimen (n = 24) between November 2000 and January 2016 at the American university of Beirut Medical Center in Lebanon. The feasibility of allogeneic stem cell transplantation (allo-SCT) for those patients was also evaluated.

RESULTS

The median follow-up time was 29 (range, 1-129) months. Fifteen (39%) and 10 (42%) patients underwent allo-SCT in the hyper-CVAD and BFM-like group, respectively. At the time of the last follow-up, 28 patients (74%) were in complete remission in the hyper-CVAD group versus 18 patients (75%) in the BFM-like group. Of those, 20 patients (53%) versus 11 patients (46%) were minimal residual disease-negative at the last follow-up, respectively. The 3-year overall survival rate (71.9% vs. 76.9%; P = .808) and 3-year disease-free survival (54.7% vs. 76.4%; P = .435) were similar in hyper-CVAD group compared with the BFM-like group, respectively. Both chemotherapies were relatively well tolerated.

CONCLUSION

Overall, despite the older age and a greater number of patients with high-risk category (including Philadelphia chromosome-positive) in the hyper-CVAD group, this did not translate into a difference in survival outcome between the 2 groups. The hyper-CVAD regimen appears to be feasible for adult patients with ALL in terms of tolerability and efficacy.

Haploidentical Transplantation with Post-Transplantation Cyclophosphamide for High-Risk Acute Lymphoblastic Leukemia

Haploidentical transplantation performed with post-transplantation cyclophosphamide (PTCy)-based graft-versus-host disease (GVHD) prophylaxis has been associated with favorable outcomes for patients with acute myeloid leukemia and lymphomas. However, it remains unclear if such approach is effective for patients with acute lymphoblastic leukemia (ALL). We analyzed outcomes of 109 consecutively treated ALL patients 18 years of age and older at 5 institutions. The median age was 32 years and the median follow-up for survivors was 13 months. Thirty-two patients were in first complete remission (CR1), while the rest were beyond CR1. Neutrophil engraftment occurred in 95% of the patients. The cumulative incidences of grades II to IV and III and IV acute GVHD at day 100 after transplantation were 32% and 11%, respectively, whereas chronic GVHD, nonrelapse mortality, relapse rate, and disease-free survival (DFS) at 1 year after transplantation were 32%, 21%, 27%, and 51%, respectively. Patients in CR1 had 52% DFS at 3 years. These results suggest that haploidentical transplants performed with PTCy-based GVHD prophylaxis provide a very suitable alternative to HLA-matched transplantations for patients with ALL.

Aberrant activation-induced cytidine deaminase expression in Philadelphia chromosome-positive B-cell acute lymphoblastic leukemia

Activation-induced cytidine deaminase (AID) is expressed in germinal center B cells and plays a critical role in somatic hypermutation and class-switch recombination of immunoglobulin genes. Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) carries a poor prognosis and is specifically treated with tyrosine kinase inhibitors. Interestingly, AID has been shown to be aberrantly expressed and functional in Ph+ ALL and is thought to contribute to genetic instability. We hypothesized that AID might be detectable in routinely processed bone marrow biopsies by immunohistochemistry (IHC) and assist in identifying Ph+ ALL. We found that AID was expressed in 26 (70%) of 37 cases of Ph+ ALL but only 1 (2.9%) of 38 cases of Ph- ALL cases. There was a significant difference in AID expression between these 2 ALL groups (P < .001, Fisher exact test). The expression of AID was confirmed by RT-PCR (reverse-transcriptase polymerase chain reaction) and correlated with IHC scoring. AID protein is expressed in a large proportion of Ph+ ALL cases at levels detectable by IHC in clinical samples and might be useful to rapidly identify cases likely to have a BCR/ABL1 fusion.

Treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults: a broader range of options, improved outcomes, and more therapeutic dilemmas

The article addresses selected key areas of flux in the management of Philadelphia chromosome-positive acute lymphoblastic leukemia. There is no doubt that tyrosine kinase inhibitors (TKIs) have made a major contribution to higher rates of complete remission and that more patients are now surviving long term. Many patients tolerate TKIs well, and remission can be achieved with minimal toxicity. Because remissions can include a proportion of patients who become BCR-ABL1 transcript negative, the question of whether allogeneic hematopoietic stem cell transplantation can be avoided requires discussion. Despite the major progress that has been made and the relative profusion of therapeutic choice compared with 10 years ago, evidence is still lacking for many of the major possible interventions, and how to combine them is unclear. Because of the rarity of the condition and the enticing possibility of increasing traction to therapy, clinical trials and international cooperation remain paramount.

Clinical significance of quantitative monitoring and mutational analysis of BCR-ABL1 transcript in Philadelphia chromosome positive B lymphoblastic leukemia

Quantitative detection of BCR-ABL1 transcript is essential in monitoring residual disease of Philadelphia chromosome positive B lymphoblastic leukemia (Ph+ B-LL). We studied the kinetics of BCR-ABL1 transcript in 41 Ph+ B-LL patients in correlation with their clinical outcome. A total of 23 patients achieved complete molecular remission at 6 months post-treatment. This was associated with a lower relapse risk and better overall survival. Likewise, sustainable complete molecular remission in 27 patients was associated with superior clinical outcome. Sporadic low level BCR-ABL1 was detected in 12 of 27 patients who had attained complete molecular remission. The relapse rate was significantly higher in non-transplant patients with persistent positive BCR-ABL1 than patients transplanted when BCR-ABL1 was detectable. All eight patients harboring ABL1 kinase domain mutations died of disease or were transferred to hospice care. We concluded that monitoring the level of BCR-ABL1 transcript after hematologic remission has predictive value to the long-term outcome.