Busulfan, fludarabine, and melphalan are effective conditioning for pediatric and young adult patients with myeloid malignancies underdoing matched sibling or alternative donor transplantation

BACKGROUND

Allogeneic hematopoietic cell transplantation (allo-HCT) remains a curative option for patients with high-risk myeloid malignancies.

PROCEDURE

We present our 10-year experience (October 2012 to October 2021) of consecutive allo-HCT in patients with myeloid malignancies treated on the pediatric HCT service and conditioned with myeloablative targeted dose-busulfan (BU), fludarabine (FLU), and melphalan (MEL). Twenty-three children, adolescents, and young adult patients (CAYA) (median age 15.4 years) with acute myeloid leukemia (AML, n = 17), myelodysplastic syndrome (MDS, n = 4), or chronic myeloid leukemia (CML, n = 2) underwent allo-HCT post-BU-FLU-MEL. Four patients had treatment-related AML/MDS. Donor/stem cell source was matched sibling donor (MSD) PBSC (n = 7), matched unrelated donor (MUD) PBSC (n = 2), umbilical cord blood (UCB) (n = 3), or haploidentical-BMT (n = 11). Risk stratification was low (n = 2), intermediate (n = 15), high (n = 3), and very high risk (n = 1). The two patients with CML had failed tyrosine kinase inhibitor therapies.

RESULTS

With a median follow-up of 41.6 months, the relapse rate is only 4.5% with an overall survival (OS) 100%, progression-free survival (PFS) 95.5%, and graft-versus-host-free-relapse-free survival (GRFS) 67.8%. The donor source and the acute graft-versus-host disease (GvHD) prophylaxis regimen significantly impacted grade II-IV aGvHD 66.7% versus 19.2% (p = .039) and chronic graft-versus-host-disease (cGvHD) 66.7% versus 0% (p = .002) in the patients receiving MSD or MUD PBSC compared to haplo-BMT, respectively, resulting in improved GRFS in haplo-BMT, 83.3% compared to 40% matched donor peripheral blood stem cell transplant (PBSCT) (p = .025).

CONCLUSIONS

Our results demonstrate that BU-FLU-MEL is efficacious conditioning for disease control in young patients with myeloid malignancies undergoing MSD or alternative donor allo-HCT, but in the setting of PBSC grafts with cyclosporine A-methotrexate (CSA-MTX) GvHD prophylaxis, it results in an unacceptably high incidence of GvHD.

Feasibility and efficacy of partially replacing post-transplant cyclophosphamide with bendamustine in pediatric and young adult patients undergoing haploidentical bone marrow transplantation

BACKGROUND

Post-transplant cyclophosphamide (PT-CY) is the most widely applied graft-versus-host disease (GvHD) prophylaxis regimen in T-cell replete haploidentical bone marrow transplantation (haplo-BMT). While PT-CY has been met with great success in the haplo-BMT arena by suppressing GvHD, patients without acute GvHD have high relapse rates.

OBJECTIVE

One of the strategies being explored by others to lessen relapse rates is the dose reduction of PT-CY. We have taken a different approach in evaluating whether partially replacing PT-CY with post-transplant bendamustine (PT-BEN) would be advantageous, which is based on our pre-clinical research that delineated several beneficial immunomodulatory properties of BEN.

STUDY DESIGN

We therefore initiated and completed a Phase Ia trial which evaluated the progressive substitution of PT-CY with PT-BEN (NCT02996773). Thirteen patients with high-risk hematologic malignancies have received PT-CY/BEN and their outcomes compared to 31 contemporaneous haplo-BMT recipients treated with the same myeloablative conditioning (MAC) regimens but receiving only PT-CY.

RESULTS

We demonstrate that partial replacement of PT-CY with PT-BEN on day +4 (PT-CY/BEN) is well tolerated and associated with significantly earlier trilineage engraftment. We also show favorable trends to significant improvements in univariate and multivariate analyses, with PT-CY/BEN compared to PT-CY, with respect to chronic GvHD (HR, 0.08; 95% CI, 0.005, 1.11; P=0.06), and GvHD-free-relapse-free survival (GRFS) (HR, 0.22; 95% CI, 0.05, 0.86; P=0.039). Our human trial has transitioned to Phase Ib which will further evaluate the safety and potential benefits of PT-CY/BEN. Herein, we also expand our pediatric, adolescent, and young adult (AYA) experience to 31 patients demonstrating an overall survival (OS), progression-free survival (PFS) and GRFS at 3 years of 85.6%, 76.1% and 58.2%, respectively in a largely racial/ethnic minority cohort.

CONCLUSIONS

PT-CY/BEN appears to be a promising treatment option that requires further evaluation.

Have CD19-directed immunotherapy and haploidentical hematopoietic cell transplantation transformed pediatric B-cell acute lymphoblastic leukemia into a chronic disease?

The treatment of pediatric B-cell acute lymphoblastic leukemia (B-ALL) has undergone several recent advancements, leading to an increased amount of treatment options for relapsed patients. The development of immunotherapies such as anti-CD19 chimeric antigen receptor(CAR) T cells and bispecific T-cell engagers has given clinicians therapeutic options with less expected toxicity when compared to standard re-induction chemotherapy. This is especially beneficial in patients with toxicities from their prior treatment. Along with this, the emergence of haploidentical hematopoietic cell transplantation (HCT) has increased opportunity for patients to receive HCT who may not have had an available matched donor. We present four patients who have received all of these therapies in different combinations to treat multiple relapses. Because of the success of achieving remission as well as decreasing toxicity, the patients are alive and well up to 15 y after the original B-ALL diagnosis, rendering this as a chronic disease for them.

Is polycystic kidney disease associated with malignancy in children?

Background

Polycystic kidney disease (PKD) is an inherited condition characterized by progressive development of end‐stage renal disease, hypertension, hepatic fibrosis, and cysts in the kidney, liver, pancreas, spleen, thyroid, and epididymis. While malignancies have been reported in association with PKD in adults, the incidence of malignancies in children with PKD is not currently known.

Methods

We report on five patients with a known history of PKD who developed a malignancy as children at the University of California, Los Angeles and the University of Colorado Anschutz Medical Campus. Patients were included from 2012 to 2017.

Results

We present five patients with a history of PKD diagnosed with a malignancy during childhood without any additional known mutations to suggest a genetic predisposition to develop cancer. This includes the first reported case of hepatocellular carcinoma in a patient with autosomal recessive polycystic kidney disease.

Conclusion

Our report illustrates the potential that PKD may be associated with an increased risk for developing cancer, even in children. Further research is necessary to better understand this relationship.

Novel association of familial testicular germ cell tumor and autosomal dominant polycystic kidney disease with PKD1 mutation

Adolescent brothers were diagnosed with testicular germ cell tumors within the same month. Both were found to have multiple renal cysts on pretreatment imaging done for staging. The proband, his brother, and their mother, were all found to have a novel splice variant in intron 8 of the PKD1 gene by clinical exome sequencing. This is the second family reported with both familial testicular germ cell tumor (FTGCT) and autosomal dominant polycystic kidney disease (ADPKD), and the first described association of FTGCT with a splice variant in PKD1. We suggest that this novel variant in PKD1 may convey increased risk for FTGCT in addition to causing ADPKD.