Peripheral Blood Haploidentical Allogeneic Stem Cell Transplantation in Older Adults with AML/MDS Demonstrates Excellent Long Term Overall Survival, Results from the Australasian Bone Marrow Transplant Recipient Registry

Background: Haploidentical Hematopoietic Stem Cell Transplantation (Haplo-HCT) is an established therapy using alternative donors for patients with Acute Myeloid Leukaemia (AML) and Myelodysplastic Syndromes (MDS). There is a limited body of evidence for older patients undergoing Haplo-HCT in AML and MDS. Studies describing Haplo-HCT in older patients have used a high proportion of bone marrow (BM) derived grafts and a variety of conditioning regimens. In this setting, Haplo-HCT demonstrates acceptable Non-Relapse Mortality (NRM) and chronic Graft Versus Host Disease (cGVHD) rates of less than 10% (Ciurea. Biology of Blood and Marrow Transplantation. 2018 Jun 1;24(6):1232-6.). In Australia and New Zealand, Haplo-HCT is predominantly performed using peripheral blood (PB). We performed a retrospective national registry study to examine the outcomes of Haplo-HCT using PB in older patients. Methods: Data was collected through the Australasian Bone Marrow Transplant Recipient Registry (ABMTRR) for patients aged 65 or older receiving a PB Haplo-HCT for AML/MDS between January 2010 and July 2020. Cumulative incidence functions were used for engraftment, CMV reactivation, acute GVHD, chronic GVHD, relapse, and NRM. The competing risk for engraftment, CMV reactivation and GVHD was death. Relapse and NRM were competing risks for each other. Overall survival (OS), relapse-free survival (RFS), and composite GVHD and RFS (GRFS) were calculated using Kaplan-Meier analyses. The impact of pre-transplant factors on these endpoints was analyzed using Cox regression. Results: A total of 44 patients were included in the analysis. The median follow-up time was 734 days. The median age was 68 (range 65-74) with a median Karnofsky Performance Status of 90. Thirty patients (68.2%) had AML while 14 (31.8%) had MDS. The median donor age was 40. The most common conditioning regimen was non-myeloablative fludarabine, cyclophosphamide and TBI (73.8%), the remainder of the patients received either melphalan or busulfan based regimens, the majority were reduced intensity with only 2 patients undergoing myeloablative conditioning. All patients received post-transplant cyclophosphamide and mycophenolate mofetil with the majority also receiving tacrolimus (90.5%) and the remainder receiving cyclosporin (9.5%). No patients received anti-thymocyte globulin. Neutrophil engraftment was achieved in 97.6% of patients, at a median of 18 days while platelet engraftment was achieved in 92.7% of patients at a median of 28 days. The cumulative incidences of CMV reactivation and CMV disease were 52.5% and 5.1% at 1 year The incidence of Grade 2-4 aGVHD was 18.2%. The incidence of cGVHD at 2 years was 40.7%, with extensive cGVHD occurring in 17.7% of patients. The incidences of relapse and NRM at 2 years were 8.8%. and 20.7% respectively. The leading causes of death were infection (64.7%) followed by relapse (14.2%). The 2-year OS was 74%. RFS and GRFS at 2 years was 70% and 48% (Figure 1). Recipient age, donor age or disease type (AML vs MDS) had no significant impact on OS or GRFS. Conclusion: These results confirm the safety and effectiveness of Haplo-HCT for AML/MDS in older patients. The rates of cGVHD were higher than expected given the lower rates reported in other studies using PTCy GVHD prophylaxis. Haplo-HCT using a PB graft demonstrates good long-term disease control with reasonable rates of NRM and cGVHD for older patients with AML/MDS. Figure 1 Figure 1. Disclosures Bajel: Abbvie, Amgen, Novartis, Pfizer: Honoraria; Amgen: Speakers Bureau. Perera: Abbvie: Speakers Bureau; BMS: Speakers Bureau. Greenwood: Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hamad: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Allogeneic Stem Cell Transplantation for Mantle Cell Lymphoma Can Achieve Durable Remission and Myeloablative Conditioning Is Associated with Inferior Survival: An Australasian Bone Marrow Transplant Recipient Registry Study

Introduction Mantle cell lymphoma (MCL) is a mature B lymphoproliferative disorder with a frequently aggressive clinical course. Although the response rates in patients eligible for conventional chemoimmunotherapy are high, relapses are virtually inevitable, with a median overall survival (OS) of three to five years. For some patients allogeneic stem haematopoietic cell transplantation (alloHCT) is a potential therapeutic option. AlloHCT for MCL has been associated with long term overall survival (OS) of around 40%, with high rates of non-relapse mortality (NRM) of 20-40% and relapse rates of 20-30% (Urbano-Ispizua et al., Biol Blood Marrow Transplant 2015;21:1746, Robinson et al., Leukemia 2015;29:464). Whilst there is evidence of a graft-versus-lymphoma effect in MCL, it has not been shown to translate into improved OS. We performed a retrospective national registry study to examine alloHCT practice and outcomes for MCL in Australia and New Zealand in the modern era. Methods Data was collected through the Australasian Bone Marrow Transplant Recipient Registry (ABMTRR) for patients receiving an alloHCT for MCL between January 2009 and December 2019. This time range was chosen to capture the era of widespread rituximab use. Survival, relapse and toxicities of alloHCT were investigated, as well as transplant trends over time. Survival was analysed using the Kaplan-Meier method, with comparisons between the transplant periods 2009-2014 and 2015-2019 performed using the log-rank test. Cox proportional hazards regression was performed to determine significant risk factors for transplant outcome. The following risk factors were analysed for impact on outcomes: age, transplant before 2015, previous autologous HCT (autoHCT), remission status at transplant, use of myeloablative conditioning (MAC), haploidentical donor and use of T cell depletion (TCD). Results A total of 86 patients were included in the analysis. The median age was 56 (range 39-71). There was a male predominance with only 12% female patients. At the time of transplant, 51% were in complete remission, 26% had a partial response and 20% had stable or progressive disease (data missing in 3%). Sixty-seven percent had undergone previous autoHCT. The majority of donors were HLA-matched siblings (51%), followed by HLA-matched-unrelated (42%) and haploidentical (7%). Myeloablative conditioning was utilised in 14%, and T-cell depletion (TCD) in 24%. The median times to neutrophil engraftment (>0.5x109/L) and platelet engraftment (>20x109/L) were 16 and 20 days respectively. NRM at 1 and 5 years was 23% (95% confidence interval [95%CI] 10-39%) and 30% (95%CI 15-48%) respectively. The 100-day cumulative incidence of grade II to IV acute GVHD was 29%. The 3-year cumulative incidence of chronic GVHD was 27%. The median duration of follow up was 4.17 years (range 0-9.6 years). Median OS was 4.2 years, with an estimated 5-year OS of 47% (95%CI 35-58%) and 10-year OS of 23% (95%CI 8-43%) (figure 1). Five-year relapse free survival (RFS) was 38% (95%CI 26-50%) (figure 2). The cumulative incidence of relapse (CIR) was 20% at 1 year and 33% at 4 years, with a flattening of the curve after this point (figure 3). On multivariate analysis (MVA), the use of myeloablative conditioning (MAC) was associated with inferior RFS (hazard ratio 2.33; 95%CI 1.05-5.17; p=0.038) and OS (hazard ratio 3.11; 95%CI 1.39-7.00; p=0.006) (figure 4). No risk factors on MVA impacted NRM or CIR. Chronic GVHD was not associated with RFS or CIR. An average of nine alloHCTs were performed each year. There was an increase in the proportion of haploidentical transplants between 2009-2014 and 2015-2019 (4% to 10%). There was no significant change over time in OS, RFS or NRM, or in the use of MAC or TCD. Conclusion There has been no significant change in the rates of alloHCT for MCL in Australia and New Zealand over the past decade. Trends show an increasing utilisation of haploidentical donors. Overall outcomes were comparable to those previously published with favourable OS and durable remissions seen in a subset of patients. MAC was associated with inferior OS and RFS, however the cause for this is unclear given the lack of association with NRM or CIR. Ongoing reporting of alloHCT outcomes in MCL is important given the emerging role of novel therapies, such as Bruton tyrosine kinase inhibitors, bispecific T cells and CAR-T cell therapy. Figure 1 Disclosures Di Ciaccio: Jansen: Honoraria, Other: travel and accomodation grant. Greenwood:MSD: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Hamad:Novartis: Honoraria; Abbvie: Honoraria.

Allogeneic Stem Cell Transplantation for Diffuse Large B Cell Lymphoma Can Achieve Durable Remissions: An Australasian Bone Marrow Transplant Recipient Registry Study

Introduction A majority of patients with diffuse large B cell lymphoma (DLBCL) will be cured with frontline chemoimmunotherapy, however a significant number of patients will relapse. Although autologous haematopoietic stem cell transplantation (autoHCT) may lead to sustained survival in some relapsing patients, long term survival with relapsed DLBCL is approximately 25% (Larouche et al., J Clin Oncol 2010;28(12):2094). Allogeneic HCT (alloHCT) is a potential treatment strategy in some DLBCL patients with relapsed disease. We performed a retrospective national registry study to examine alloHCT practice and outcomes for DLBCL in Australia and New Zealand in the modern era. Methods Data was collected through the Australasian Bone Marrow Transplant Recipient Registry (ABMTRR) for patients receiving an alloHCT for DLBCL between January 2009 and December 2019. Survival was analysed using the Kaplan-Meier method, with comparisons between the transplant periods 2009-2014 and 2015-2019 performed using the log-rank test. Both univariate and Cox proportional hazards regression were performed to determine significant risk factors for transplant outcome. The following risk factors were analysed for impact on outcomes: age, transplant before 2015, previous autoHCT, remission status at transplant, use of myeloablative conditioning (MAC), haploidentical donor (HD) and use of T cell depletion (TCD). Results A total of 154 patients were included in the analysis. The median age was 52 years (range 19-71) and 68% were male. Disease status at transplant was complete remission (CR) in 49%, partial response in 31% and stable or progressive disease in 17% (missing data in 3%). Fifty-five per cent had undergone a previous autoHCT. Approximately equal proportions of donors were HLA-matched siblings or matched unrelated (45% and 46% respectively) and 9% were HDs. MAC was utilised in 26%, and TCD in 24% (alemtuzumab in 3%, anti-thymocyte globulin in 21%) (data missing in 12%). The median times to neutrophil engraftment and platelet engraftment were 16 and 18 days respectively. Non-relapse mortality (NRM) at 1-year and 5-years was 20% (95%CI 7-30%) and 26% (95%CI: 13-38%). The 100-day cumulative incidence of grade II to IV acute graft versus host disease was 15% (95%CI 5-31%). The 3-year cumulative incidence of chronic graft versus host disease (cGVHD) was 56% (95%CI 46-65%) (figure 1). The median duration of follow up for the cohort was 3.98 years (range 0-9.64 years). Median overall survival (OS) post-transplant was 4.01 years, with 5-year OS of 47% (95%CI 38-56%) and 10-year OS of 40% (95%CI 26-54%) (figure 2). The 5-year relapse free survival (RFS) was 45% (95%CI 26-50%) (figure 3). The cumulative incidence of relapse (CIR) was 21% at 1 year and 32% at four years, however relapses were not seen after this point, suggesting a subpopulation with durable remissions (figure 4). On univariate analysis, TCD was associated with both reduced incidence of cGVHD (HR 0.35 95%CI 0.19-0.66, p=0.012) and increased NRM (HR 2.10 95%CI 0.88-4.99 p=0.043). These associations were maintained on multivariate analysis (MVA) (HR 0.29 95%CI 0.16-0.76, p=0.011; HR 2.19 95%CI 1.02-4.70, p=0.045) (figures 5, 6). TCD did not impact on RFS. The vast majority of TCD was given in unrelated donor alloHCTs. CR at time of transplant was associated with improved RFS on univariate analysis (HR 1.65 95%CI 1.04-2.64, p=0.034), however this association was not seen on MVA. No other analysed risk factors impacted OS, RFS, NRM, CIR or GVHD rates on either univariate or MVA. An average of 14 alloHCTs were performed each year, with a trend towards increasing annual numbers over time. There was a significant increase in the proportion of haploidentical transplants between 2009 and 2019 (p=0.003), though total numbers were low (n=14). There was no significant change over time for the use of MAC, TCD, nor in OS, RFS or NRM. Conclusion There has been an increase in the rates of alloHCT with HDs for DLBCL in Australia and New Zealand over the past decade. Survival and relapse rates are relatively favourable compared to the published literature, with sustained remissions observed (5 and 10-year OS of 47% and 40% respectively). TCD is associated with reduced cGVHD rates, as well as increased NRM. Ongoing reporting of alloHCT outcomes in DLBCL is important given the emerging role of novel therapies such as bispecific monoclonal antibodies and chimeric antigen receptor T cell therapy. Figure 1 Disclosures Di Ciaccio: Jansen: Honoraria, Other: travel and accomodation grant. Greenwood:Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Spencer:Celgene, Janssen and Takeda: Speakers Bureau; AbbVie, Amgen, Celgene, Haemalogix, Janssen, Sanofi, SecuraBio, Specialised Therapeutics Australia, Servier and Takeda: Honoraria; Amgen, Celgene, Haemalogix, Janssen, Servier and Takeda: Research Funding; AbbVie, Celgene, Haemalogix, Janssen, Sanofi, SecuraBio, Specialised Therapeutics Australia, Servier and Takeda: Consultancy. Arthur:Royal North Shore Hospital: Current Employment. Hamad:Novartis: Honoraria; Abbvie: Honoraria.