Reduced Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation for Acute Lymphoblastic Leukemia; Current Evidence, and Improving Outcomes Going Forward

Family Caregiver Experiences in the Inpatient and Outpatient Reduced-Intensity Conditioning Allogeneic Hematopoietic Cell Transplantation Settings: A Qualitative Study

Caregivers (ie, family and friends) are essential in providing care and support for patients undergoing hematopoietic cell transplantation (HCT) and throughout their recovery. Traditionally delivered in the hospital, HCT is being increasingly provided in the outpatient setting, potentially heightening the burden on caregivers. Extensive work has examined the inpatient HCT caregiving experience, yet little is known about how caregiver experiences may differ based on whether the HCT was delivered on an inpatient or outpatient basis, particularly during the acute recovery period post-HCT. This study explored the similarities and differences in caregiver experiences in the inpatient and outpatient settings during the early recovery from reduced-intensity conditioning (RIC) allogeneic HCT. We conducted semistructured interviews (n = 15) with caregivers of adults undergoing RIC allogeneic HCT as either an inpatient (n = 7) or an outpatient (n = 8). We recruited caregivers using purposeful criterion sampling, based on the HCT setting, until thematic saturation occurred. Interview recordings were transcribed and coded through thematic analysis using Dedoose v.9.0. The study analysis was guided by the transactional model of stress and coping and the model of adaptation of family caregivers during the acute phase of BMT. Three themes emerged to describe similar experiences for HCT caregivers regardless of setting: (1) caregivers reported feeling like they were a necessary yet invisible part of the care team; (2) caregivers described learning to adapt to changing situations and varying patient needs; and (3) caregivers recounted how the uncertainty following HCT felt like existing between life and death while also maintaining a sense of gratitude and hope for the future. Caregivers also reported distinct experiences based on the transplantation setting and 4 themes emerged: (1) disrupted routines: inpatient caregivers reported disrupted routines when caring for the HCT recipient while simultaneously trying to manage non-caregiving responsibilities at home and work, and outpatient caregivers reported having to establish new routines that included frequent clinic visits with the patient while altering or pausing home and work responsibilities; (2) timing of caregiver involvement: inpatient caregivers felt more involved in care after the patient was discharged from the HCT hospitalization, whereas outpatient caregivers were already providing the majority of care earlier in the post-transplantation period; (3) fear of missing vital information: inpatient caregivers worried about missing vital information about the patient's care and progress if not physically present in the hospital, whereas outpatient caregivers feared overlooking vital information that may warrant contacting the care team as they monitored the patient at home; and (4) perceived adequacy of resources to meet psychosocial and practical needs: inpatient caregivers reported having adequate access to resources (ie, hospital-based services), whereas outpatient caregivers felt they had more limited access and needed to be resourceful in seeking out assistance. Inpatient and outpatient HCT caregivers described both similar and distinct experiences during the acute recovery period post-HCT. Specific interventions should address caregiver psychosocial needs (ie, distress, illness uncertainty, communication, and coping) and practical needs (ie, community resource referral, preparedness for home-based caregiving, and transplantation education) of HCT caregivers based on setting.

Total body irradiation versus busulfan based intermediate intensity conditioning for stem cell transplantation in ALL patients >45 years-a registry-based study by the Acute Leukemia Working Party of the EBMT

Allogeneic hematopoietic cell transplantation is a potentially curative treatment in high-risk acute lymphoblastic leukemia (ALL). Conditioning regimens based on ≥12 Gray total body irradiation (TBI) represent the current standard in patients ≤45 years, whereas elderly patients frequently receive intermediate intensity conditioning (IIC) to reduce toxicity. To evaluate the role of TBI as a backbone of IIC in ALL, a retrospective, registry-based study included patients >45 years transplanted from matched donors in first complete remission, who had received either fludarabine/TBI 8 Gy (FluTBI8, n = 262), or the most popular, irradiation-free alternative fludarabine/busulfan, comprising busulfan 6.4 mg/kg (FluBu6.4, n = 188) or 9.6 mg/kg (FluBu9.6, n = 51). At two years, overall survival (OS) was 68.5%, 57%, and 62.2%, leukemia-free survival (LFS) was 58%, 42.7%, and 45%, relapse incidence (RI) was 27.2%, 40%, and 30.9%, and non-relapse-mortality (NRM) was 23.1%, 20.7%, and 26.8% for patients receiving FluTBI8Gy, FluBu6.4, and FluBu9.6, respectively. In multivariate analysis, the risk of NRM, acute and chronic graft-versus-host disease was not influenced by conditioning. However, RI was higher after FluBu6.4 (hazard ratio [HR] [95% CI]: 1.85 [1.16-2.95]), and LFS was lower after both FluBu6.4 (HR: 1.56 [1.09-2.23]) and FluBu9.6 (HR: 1.63 [1.02-2.58]) as compared to FluTBI8. Although only resulting in a non-significant advantage in OS, this observation indicates a stronger anti-leukemic efficacy of TBI-based intermediate intensity conditioning.

Intensity of induction regimen and outcomes among adults with Ph+ALL undergoing allogeneic hematopoietic stem cell transplantation

Tyrosine kinase inhibitors (TKIs) are essential for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) and have allowed for effective, low intensity induction regimens including no or minimal chemotherapy. Whether the use of low intensity induction regimens impacts outcomes after allogeneic hematopoietic stem cell transplant (alloHCT) is less understood. We identified consecutive adult patients with Ph+ ALL undergoing alloHCT in first complete remission (CR1) at our center from 2010 to 2021 and examined the impact of pre-transplant induction intensity on outcomes. Among the 87 identified patients, 44 (51%) received low intensity induction and 43 (49%) received induction with high intensity chemotherapy. Patients receiving low intensity induction were older (median age 60 vs. 47 years, p < 0.01). Following induction, measurable residual disease (MRD) negativity by BCR::ABL1 RT-PCR was similar in the low and high intensity induction cohorts (54% and 52% respectively). Receipt of reduced intensity transplant conditioning was not associated with intensity of induction regimen (39% vs. 19% in low vs. high, respectively, p = 0.06). At a median follow-up of 21 months from transplant, there was no difference between low and high intensity induction with respect to 2-year disease-free survival (58% vs. 56%), 2-year overall survival (62% vs. 63%), 2-year cumulative incidence of relapse (9% vs. 17%), and 2-year non-relapse mortality (33% vs. 29%). We also found no difference in outcomes when patients were segmented by both induction and conditioning regimen intensities. Our retrospective analysis suggests that induction intensity does not impact post-transplant outcomes among patients with Ph+ ALL transplanted in CR1.

Worked to the bone: antibody-based conditioning as the future of transplant biology

Conditioning of the bone marrow prior to haematopoietic stem cell transplant is essential in eradicating the primary cause of disease, facilitating donor cell engraftment and avoiding transplant rejection via immunosuppression. Standard conditioning regimens, typically comprising chemotherapy and/or radiotherapy, have proven successful in bone marrow clearance but are also associated with severe toxicities and high incidence of treatment-related mortality. Antibody-based conditioning is a developing field which, thus far, has largely shown an improved toxicity profile in experimental models and improved transplant outcomes, compared to traditional conditioning. Most antibody-based conditioning therapies involve monoclonal/naked antibodies, such as alemtuzumab for graft-versus-host disease prophylaxis and rituximab for Epstein–Barr virus prophylaxis, which are both in Phase II trials for inclusion in conditioning regimens. Nevertheless, alternative immune-based therapies, including antibody–drug conjugates, radio-labelled antibodies and CAR-T cells, are showing promise in a conditioning setting. Here, we analyse the current status of antibody-based drugs in pre-transplant conditioning regimens and assess their potential in the future of transplant biology.

Conditioning Regimens for Frail Patients with Acute Leukemia Undergoing Allogeneic Stem Cell Transplant: How to Strike Gently

Despite the recent dramatic progress in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) therapy, allogeneic transplant remains a mainstay of treatment for patients with acute leukemia. The availability of novel compounds and low intensity chemotherapy regimens made it possible for a significant proportion of elderly and comorbid patients with AML or ALL to undergo curative treatment protocols. In addition, the expansion of donor availability and the recent dramatic progress in haploidentical stem cell transplant, allow the identification of an available donor for nearly every patient. Therefore, an increasing number of transplants are currently performed in elderly and frail patients with AML or ALL. However, allo-Hematopoietic stem cell transplant (HSCT) in this delicate setting represents an important challenge, especially regarding the selection of the conditioning protocol. Ideally, conditioning intensity should be reduced as much as possible; however, in patients with acute leukemia relapse remains the major cause of transplant failure. In this article we present modern tools to assess the patient health status before transplant, review the available data on the outcome of frail AML an ALL patients undergoing allo-HSCT, and discuss how preparatory regimens can be optimized in this setting.

INCB84344-201: Ponatinib and steroids in frontline therapy of unfit patients with Ph+ acute lymphoblastic leukemia

In patients with newly diagnosed Ph⁺ ALL, ponatinib and prednisone therapy resulted in long molecular remissions and few resistance mutations.

The observed high rates of discontinuation and dose modification suggest that a lower dose may be more appropriate in older/unfit patients.

Tyrosine kinase inhibitors have improved survival for patients with Philadelphia chromosome–positive (Ph⁺) acute lymphoblastic leukemia (ALL). However, prognosis for old or unfit patients remains poor. In the INCB84344-201 (formerly GIMEMA LAL 1811) prospective, multicenter, phase 2 trial, we tested the efficacy and safety of ponatinib plus prednisone in newly diagnosed patients with Ph⁺ ALL ≥60 years, or unfit for intensive chemotherapy and stem cell transplantation. Forty-four patients received oral ponatinib 45 mg/d for 48 weeks (core phase), with prednisone tapered to 60 mg/m²/d from days-14-29. Prophylactic intrathecal chemotherapy was administered monthly. Median age was 66.5 years (range, 26-85). The primary endpoint (complete hematologic response [CHR] at 24 weeks) was reached in 38/44 patients (86.4%); complete molecular response (CMR) in 18/44 patients (40.9%) at 24 weeks. 61.4% of patients completed the core phase. As of 24 April 2020, median event-free survival was 14.31 months (95% CI 9.30-22.31). Median overall survival and duration of CHR were not reached; median duration of CMR was 11.6 months. Most common treatment-emergent adverse events (TEAEs) were rash (36.4%), asthenia (22.7%), alanine transaminase increase (15.9%), erythema (15.9%), and γ-glutamyltransferase increase (15.9%). Cardiac and vascular TEAEs occurred in 29.5% (grade ≥3, 18.2%) and 27.3% (grade ≥3, 15.9%), respectively. Dose reductions, interruptions, and discontinuations due to TEAEs occurred in 43.2%, 43.2%, and 27.3% of patients, respectively; 5 patients had fatal TEAEs. Ponatinib and prednisone showed efficacy in unfit patients with Ph⁺ ALL; however, a lower ponatinib dose may be more appropriate in this population. This trial was registered at www.clinicaltrials.gov as #NCT01641107.

Inferior outcomes with reduced intensity conditioning followed by allogeneic hematopoietic cell transplantation in fit individuals with acute lymphoblastic leukemia: a Canadian single-center study and a comparison to registry data

Allogeneic hematopoietic cell transplantation (HCT) can offer cure to some patients with acute lymphoblastic leukemia (ALL). It remains unclear how conditioning intensity affects transplant outcomes in ALL. In this retrospective study, we compared outcomes between 27 patients <60 who received reduced intensity conditioning (RIC) at Princess Margaret Hospital Cancer Center (PMCC) and 226 Cell Therapy Transplant Canada (CTTC) age-matched controls who received myeloablative conditioning (MAC) between 2007 and 2018. Compared to CTTC patients, PMCC patients had an inferior 2-y OS: 0.29 (95% CI: 0.11-0.49) vs 0.63 (0.56-0.70), HR = 2.10 (1.23-3.55), p = 0.006, higher TRM: 0.41 (0.22-0.60) vs 0.24 (0.18-0.30), HR = 2.00 (1.05-3.81), p = 0.04 and a trend toward increased risk of relapse: 0.36 (0.17-0.56) versus 0.17 (0.12-0.22), HR = 1.72 (0.82-3.62), p = 0.15. In multivariate analysis, RIC and the use of T-cell depletion (TCD) were associated with inferior OS. In ALL patients <60, the use of RIC with TCD is associated with inferior allogeneic HCT outcomes.

Reduced-Intensity Conditioning with Busulfan and Fludarabine for Allogeneic Hematopoietic Stem Cell Transplantation in Acute Lymphoblastic Leukemia

PURPOSE

Allogeneic hematopoietic stem cell transplantation (HSCT) with optimal conditioning has helped better long-term survival in acute lymphoblastic leukemia (ALL). This study investigated the efficacy and safety of reduced-intensity conditioning (RIC) with busulfan and fludarabine in adult ALL patients unfit for myeloablation.

MATERIALS AND METHODS

Records of 78 patients who underwent HSCT with RIC consisting of 3.2 mg/kg/day of busulfan for 2 or 3 days and 30 mg/m²/day of fludarabine for 5 or 6 days were analyzed.

RESULTS

The median age at diagnosis was 49 years. Over a median follow-up of 22 months, 2-year estimates of relapse-free survival (RFS) and overall survival were 57.4% and 68.7%, respectively. Multivariate analysis showed a trend of improved RFS in patients with chronic graft-versus-host disease (GVHD) (hazard ratio, 0.53; 95% confidence interval, 0.26-1.08; p=0.080). The cumulative incidences of relapse and non-relapse mortality were 42.9% and 19.6%, respectively and one case of central nervous system relapse was noted. No hepatic veno-occlusive disease was reported. Grade II-IV acute GVHD and any grade chronic GVHD occurred in 21.1% and 41.7%, respectively.

CONCLUSION

RIC with busulfan and fludarabine is an effective and safe conditioning regimen for adult ALL patients unfit for myeloablation.

Use of chimeric antigen receptor T cells in allogeneic hematopoietic stem cell transplantation

The chimeric antigen receptor T (CAR-T) cells play an antileukemia role, and can be used to treat or prevent relapse by targeting minimal residual disease for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the infusion of allogeneic CAR-T cells may also cause graft-versus-host disease, which limited their applications during and after allo-HSCT. In this review, we discuss the clinical trials that applying CAR-T cells before allo-HSCT and the use of donor-derived CAR-T cells as conditioning regimen during allo-HSCT. At last, we analyzed the effect of donor-derived CAR-T cells on preventive infusion after allo-HSCT.

Transplantation in adults with relapsed/refractory acute lymphoblastic leukemia who are treated with blinatumomab from a phase 3 study

BACKGROUND

Blinatumomab, a bispecific T-cell-engaging (BiTE®) immuno-oncology therapy, demonstrated superior overall survival versus standard-of-care chemotherapy (SOC) in adults with relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R ALL) in the phase 3 TOWER study. Herein, the authors reported clinical features and outcomes for those patients who underwent allogeneic hematopoietic stem cell transplantation (HSCT) after treatment with blinatumomab.

METHODS

In the TOWER study, adults with R/R ALL were randomized 2:1 to receive blinatumomab or SOC. Study treatment consisted of 2 cycles of induction with blinatumomab or SOC followed by consolidation and maintenance therapy. At any time after the first cycle, patients who were eligible for HSCT could proceed to HSCT.

RESULTS

Of the 97 patients who underwent HSCT during the study, baseline characteristics generally were comparable and donor types were similar between the patients treated with blinatumomab (65 patients) and those receiving SOC (32 patients). There was no evidence to suggest that the survival benefit of HSCT differed between the patients treated with blinatumomab and those receiving SOC (P = .68). On the basis of descriptive statistics, a survival benefit of HSCT versus no HSCT was not observed in patients who achieved complete remission with full, partial, or incomplete hematologic recovery with blinatumomab (odds ratio, 1.17; 95% CI, 0.54-2.53). The best outcomes were achieved in patients with no prior salvage therapy and with minimal residual disease response to blinatumomab regardless of on-study HSCT status.

CONCLUSIONS

Survival was found to be driven by response to study treatment and by salvage status regardless of on-study HSCT status. These data should be interpreted with caution because the current study was not designed to prospectively assess survival outcomes associated with HSCT after blinatumomab.

LAY SUMMARY

Evidence before this study: Blinatumomab is associated with superior morphologic and molecular response rates and superior overall outcome when compared with standard of care chemotherapy in adults with relapsed/refractory B-cell precursor acute lymphoblastic leukemia. Added value of this study: The best outcomes with blinatumomab were observed in patients who achieved minimal residual disease remission in first salvage treatment regardless of subsequent allogeneic stem cell transplantation (HSCT). Implications of all the available evidence: Patients achieving CR/CRh/CRi following blinatumomab can have a durable response with or without HSCT.

Approach to the Adult Acute Lymphoblastic Leukemia Patient

During recent decades, understanding of the molecular mechanisms of acute lymphoblastic leukemia (ALL) has improved considerably, resulting in better risk stratification of patients and increased survival rates. Age, white blood cell count (WBC), and specific genetic abnormalities are the most important factors that define risk groups for ALL. State-of-the-art diagnosis of ALL requires cytological and cytogenetical analyses, as well as flow cytometry and high-throughput sequencing assays. An important aspect in the diagnostic characterization of patients with ALL is the identification of the Philadelphia (Ph) chromosome, which warrants the addition of tyrosine kinase inhibitors (TKI) to the chemotherapy backbone. Data that support the benefit of hematopoietic stem cell transplantation (HSCT) in high risk patient subsets or in late relapse patients are still questioned and have yet to be determined conclusive. This article presents the newly published data in ALL workup and treatment, putting it into perspective for the attending physician in hematology and oncology.

Dasatinib as an investigational drug for the treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults

INTRODUCTION

Acute lymphoblastic leukemia (ALL) with BCR-ABL1 translocation is an aggressive malignancy that is usually treated with intensive chemotherapy with the possibility of allogeneic stem cell transplantation. The encoded fusion protein may be important for leukemogenesis; clinical studies show that dasatinib has an antileukemic effect in combination with steroids alone or intensive chemotherapy. Areas covered: Relevant publications were identified through literature searches (the used terms being acute lymphoblastic leukemia plus dasatinib) in the PubMed database. We searched for original articles and reviews describing the pharmacology and clinical use of dasatinib in ALL with BCR-ABL1. The mechanism of action, pharmacology and clinical study findings are examined. Expert opinion: Dasatinib is associated with a high complete remission rate in ALL when used alone and in combination with steroids or intensive chemotherapy. However, mutations at T315 and F317 are associated with dasatinib resistance. Overall toxicity has been acceptable in these studies and no unexpected toxicity was observed. It is not known whether the antileukemic effect of dasatinib differs between subsets of BCR-ABL1⁺ patients or is attributed to inhibition of the fusion protein alone, or a combined effect on several kinases, and whether dasatinib-containing combination treatment should be preferred in these patients instead of other emerging strategies, e.g. monoclonal antibodies.