Baranwal, Anmol

7038 Background: While chimeric antigen receptor T-cell (CAR-T) therapy has transformed treatment for hematological malignancies, severe (≥ grade 3,Gr 3, CTCAE) cytopenias post CAR-T and therapy related myeloid neoplasms (t-MN) are particularly difficult to manage. Survival after diagnosis of t-MN is dismal. Management of ≥Gr 3 cytopenias that do not recover by month 3 after CAR-T require frequent monitoring and transfusion support. Growth factor and thrombopoietin mimetics have variable success, with stem cell boost emerging as having more consistent success. Evaluation for CAR-T eligibility, prior to leukapheresis, is the critical timepoint where factors identified at this time could inform risks and benefits of CAR-T versus alternative treatment and for consideration of stem cell collection in patients who may benefit from stem cell boost to treat severe cytopenia post CAR-T. Methods: We conducted a retrospective analysis comparing clinical data of patients (pts) with lymphoma (NHL) and multiple myeloma (MM) treated with FDA-approved and investigational CAR-T between 01/2016 – 06/2022 at Mayo Clinic. Prolonged cytopenias were defined as hemoglobin (Hg)<8 g/dL, absolute neutrophil count (ANC)<0.5 x 109/L, and/or platelet count (PLT)<50 x 109/L at 3 months after CAR-T. Pts with progressive disease were excluded from cytopenia analysis. Logistic regression to identify factors correlated with cytopenia and t-MN. Results: Among the 186 pts who received CAR-T, 42 (22%) patients developed severe cytopenia (26/102, 25%, in NHL; 16/84, 19% in MM); 15/186 (8%) had more than 1 concurrent cytopenia. Univariate analysis identified that baseline ferritin and CAR-HEMATOTOX score correlated with cytopenia. Multivariate analysis showed that advanced age (≥ 65 years) (HR 2.69, 95%CI 1.17 – 6.40, P = 0.02) and thrombocytopenia (HR 4.01, 95%CI 1.77 – 9.34, P = 0.001) were associated with severe cytopenia. Twenty (10.7%) patients [8 (40%) males] developed t-MN at a median of 9.5 months (IQR 4.8 – 19.3 months) after CAR-T (14/102, 13% in NHL; 6/84, 7% in MM). Univariate analysis identified ferritin and CAR-HEMATOTOX score correlated with t-NM. Multivariate logistic regression showed advanced age (HR 5.03; 95%CI 1.59-18.7, P= 0.009), hemoglobin ≤ 10 g/dl (HR 3.63, 95%CI 1.04-13.30, P = 0.04), and thrombocytopenia (HR 4.06, 95%CI 1.32-14.2, P 0.02) are significantly associated with development of post-CART t-MN. Conclusions: Advanced age, anemia and thrombocytopenia at the time of evaluation for CAR-T eligibility, prior to leukapheresis, are associated with the development of post-treatment severe cytopenia and t-MN. Larger, multi-center studies are needed to validate these findings.

Abstract Clonal cytopenia of undetermined significance (CCUS) is defined by a myeloid driver mutation in the context of otherwise unexplained cytopenia. CCUS has an inherent risk of progressing to myeloid neoplasm. However, it is unknown how exposure to previous cytotoxic therapy may impact the risk of progression and survival. We stratified patients with CCUS by prior exposure to DNA-damaging therapy. Of 151 patients, 46 (30%) had received cytotoxic therapy and were classified as therapy-related CCUS (t-CCUS), whereas 105 (70%) had de novo CCUS. A lower proportion of t-CCUS had hypercellular marrows (17.8% vs 44.8%, P = .002) but had higher median bone marrow blast percentages. After a median follow-up of 2.2 years, t-CCUS had significantly shorter progression-free survival (PFS, 1.8 vs 6.3 years; hazard ratio [HR], 2.1; P = .007) and median overall survival (OS; 3.6 years vs not reached; HR, 2.3; P = .007) compared with CCUS. Univariable and multivariable time-to-event analyses showed that exposure to cytotoxic therapy independently accounted for inferior PFS and OS. Despite the similarities in clinical presentation between CCUS and t-CCUS, we show that exposure to prior cytotoxic therapies was an independent risk factor for inferior outcomes. This suggests that t-CCUS represents a unique clinical entity that needs more stringent monitoring or earlier intervention strategies.

This case-control study examines the incidence and risks of myeloid neoplasms in adults treated for B-cell lymphoproliferative disorders or multiple myeloma.

BACKGROUND: Recent World Health Organization (WHO) classifications (5 th edition), International Consensus Classification (ICC) recognized TP53-mutated ( TP53mut) myeloid neoplasms (MNs) as a distinct subcategory, acknowledging their uniformly poor outcomes. However, there are critical differences between the two guidelines in how TP53 allelic status is assigned. Both WHO-5 and ICC acknowledged the poor outcome of multi-hit TP53mut but excluded single-hit TP53mut. These changes are driven by a pivotal study demonstrating favourable outcome of single-hit TP53mut, however this study predominantly included de novo myelodysplastic syndromes (MDS) cases (Bernard et al. Nat Med 2020). In contrast, we previously reported poor outcome of TP53mut therapy-related myeloid neoplasm (t-MN) irrespective of the allelic status of TP53 (Hiwase et al Blood 2022andShah et al BCJ 2023). Finally, the ICC removed the subcategory of “therapy-related,” substituting it with diagnostic qualifiers instead. The WHO has grouped t-MN with secondary MN and renamed it as “myeloid neoplasm post cytotoxic therapy,” with the assertion that only multi-hit T P53mut MDS occurring post-cytotoxic therapy have poor outcome compared with single-hit. METHODS: We analyzed one of the largest international cohorts of TP53mut MN (n=544) with full characterization of TP53mut allele status utilizing uniform ICC criteria and similar large numbers of de novo and t-MN cases managed at Mayo Clinic Enterprise (USA) and South Australian MDS Registry, Adelaide (Australia) with clinical, integrated genomic profiling, and long-term follow-up. RESULTS: In our cohort of TP53mut MN (n=544), 475 (87.3%) MN had TP53mut variant allele frequency (VAF) of ≥10% and thus satisfied ICC criteria for TP53mut MN. Majority of TP53mut t-MN presented with MDS (bone marrow (BM) blasts 0-9%) compared de novo MN (62% vs. 48%; P=0.0012). While acute myeloid leukemia (AML) (BM blasts ≥20%) were more prevalent in TP53mutde novo MN compared to t-MN (38% vs. 24%; P= 0.001) and there was no difference in frequency of MDS/AML (BM blasts 10-19%) between the two cohorts (14% vs. 14%; P=0.8) ( Figure 1A). Majority of TP53mut were observed in the DNA-binding domain in t-MN and de novo MN (95% vs. 96.2%; P=0.48). However, mutations in Tetramer Domain were more frequent in t-MN (4.3% vs. 0.3%; P=0.002), whereas those in the TAD2 domain were more frequent in de novo TP53mut MN (2.4 vs. 0%; P =0.006). Integrating the mutation, conventional G-banding cytogenetic, copy number variation (CNV), FISH, and SNP array analysis, TP53mut MDS (BM blast 0-9%; n=260) were classified as multi-hit (n=179, 68.9%) or multi-equivalent (n=35, 13.5%) and single-hit (n=46, 17.7%) (Arber et al. Blood 2022). Striking enrichment of multi-hit/multi-hit equivalent was observed in TP53mut t-MDS compared to de novo MDS (91% vs. 72%; P&lt;0.0001). While single-hit TP53mut were prevalent in de novo MDS compared to t-MDS (28% vs. 9%; P&lt;0.0001). Importantly, median overall survival (OS) of single-hit was significantly longer than multi-hit de novo MDS (25.4 vs. 7.2 months; P=0.0002). In contrast to this we did not observe OS difference between single-hit and multi-hit TP53mut t-MDS (11.6 vs. 10.9 months; P =0.73) ( Figure 1B). CONCLUSION: Our study based on a large international cohort of T53mut MN provides compelling evidence that in contrast to de novo MDS, single hit TP53mut t-MDS is associated with poor outcome. Our data supports the consideration of single hit t-MDS as a multi-hit equivalent.

Introduction: Fludarabine combined with melphalan 140 mg/m2 (FluMel140) is a commonly used reduced-intensity conditioning (RIC) regimen in patients undergoing matched related (MRD) and unrelated donor (MUD) allogeneic stem cell transplant (alloSCT). Ciurea et al Blood 2020, described outcomes of Flu 160 mg/m2 and Mel 100 mg/m2. In this study, we describe our experience of attenuated melphalan dosing 100-120 mg/m2 versus 140 mg/m2 with fludarabine 125 mg/m2 (attenuated FluMel versus regular dose FluMel). Methods: We retrospectively reviewed patients from November 2016 to April 2023 with AML, ALL or MDS undergoing alloSCT who received fludarabine and melphalan. Patients who received the lower dose of melphalan were considered to be the attenuated FluMel cohort, whereas patients receiving the melphalan 140 mg/m2 were considered to be the control cohort. Kaplan-Meier and log-rank tests were used to estimate OS. NRM and relapse incidence (RI) was calculated using competing risk analysis. R 4.2.0 (R Foundation for Statistical Computing) was used for statistical analyses. Results: A total of 134 patients [92 (68.7%) males] were evaluated. Thirty-seven (27.6%) patients received attenuated FluMel and 97 (72.4%) patients received regular dose FluMel (controls). Among the patients in the attenuated FluMel cohort, 5 (13.5%) patients also received fludarabine at doses less than 125 mg/m 2 [median 20 mg/m 2 (range 87.5-112.5 mg/m 2]. Median age at transplant was 65 years (range 30 - 76 years). The most common disease was AML [75 (56.0%) patients] ( Table 1). Patients in the attenuated FluMel group had comparable iothalamate clearance compared to control cohort (clearance &lt;65 ml/min/1.73 m2: 18.9% vs. 12.4%, P = 0.52). Patients in the attenuated FluMel group had comparable rates of high/very high DRI to those in control cohort (51.4% vs. 43.3%, P = 0.91). Compared to the control cohort, patients in the attenuated FluMel group were less likely to have a matched related donor (21.6% vs. 45.4%, P = 0.02) and were more likely to receive PTCy for GVHD prophylaxis (37.8% vs. 16.5%, P = 0.02). Among the patients receiving attenuated FluMel, the median melphalan dose administered was 100 mg/m2. The median time to neutrophil engraftment was 19 days (IQR 16-21 days), and median time to platelet engraftment was 18 days (range 12-25 days). Eleven (29.7%) patients developed post-alloSCT mucositis, and 3 (8.1%) patients developed grade 3-4 mucositis. All the patients in the attenuated FluMel group achieved 100% CD33 donor chimerism at day +30 (n=35) and day +100 (n=28) after alloSCT. Similarly, 26 (74.3%, n = 35) patients achieved ≥ 95% CD3 donor chimerism at day +30 after alloSCT and 23 (82.1%, n = 28) patients achieved ≥ 95% CD3 donor chimerism at day +100 after alloSCT. Median follow-up of the entire cohort after alloSCT was 2.3 years (95% CI 2.1-2.5 years). Median follow-up was 1.5 years in the attenuated FluMel cohort and 2.5 years for the control cohort ( P&lt;0.001) . Survival was similar among patients receiving attenuated FluMel vs. control cohort (2-year OS 74.7% vs. 65.0%, P = 0.28). At 2 years post-alloSCT, the attenuated FluMel and control cohort had similar non-relapse mortality (19.9% vs. 24.4%, P=0.58) and relapse (22% vs. 15.2%, P=0.51). The attenuated FluMel was not associated with an increased incidence of relapse (HR 1.36, 95% CI 0.50-3.73, P=0.55) or NRM (HR 0.74, 95% CI 0.28-1.95, P = 0.55). GVHD-free relapse free (GRFS) survival was also similar among the attenuated Flu/Mel and control cohort (1-year GRFS rate 41.1% vs. 45.6%, P = 0.8). Among the patients receiving PTCy for GVHD prophylaxis, the 2-year OS in patients receiving attenuated FluMel was higher than the control group, but it was not statistically significant (2-year OS rate: 90% vs. 55%, P=0.37, Figure 1). Compared to the control group, the attenuated FluMel group had similar rates of NRM at 100 days (10% vs. 12.5%), 1 year (NA vs. 25%) and at 2 years after alloSCT (NA vs. 25%, P=0.54). GRFS at 1 year was also similar between the attenuated FluMel and control group (68.6% vs. 43.8%, P = 0.69). Conclusion: The attenuated dosed FluMel conditioning is a safe and effective regimen for elderly patients with acute leukemia and MDS, and is non-inferior to regular dose FluMel. Among patients receiving PTCy for GVHD prophylaxis, the lower dose of melphalan was non-inferior to regular dose FluMel for survival outcomes. Larger studies are needed to confirm our findings.

BACKGROUND: Recently proposed World Health Organization (WHO, 5 th edition) and International Consensus Classification (ICC) recognized myeloid neoplasms (MN) harboring TP53-mutated ( TP53mut) as a separate entity. However, there are critical differences between the two classifications regarding allelic-status, variance allele frequency (VAF) cut-off and blast categories, that may lead to under- or overestimation of the risk. METHODS: We analyzed MN harboring TP53mut (VAF ≥2%, n=536) managed at Mayo Clinic (USA) and South Australia Health Network (Australia). ICC (Arber et al, Blood 2022) and WHO (Bluebook, Beta v2) definitions were used to stratify MN harboring TP53mut. RESULTS: Of 536 cases, 379 (71%) had myelodysplastic syndromes (MDS) (&lt;20% blasts) and 157 (29%) had acute myeloid leukemia (AML). Using WHO, 160 (42%) of 379 were classified as MDS-bi TP53 as they harbored 2 TP53mut (n=115; 30%) or 1 TP53mut plus confirmed loss of heterozygosity (LOH) or copy neutral LOH (cnLOH) of TP53 locus (n=45; 12%). Sixty-two (16%) TP53mut MDS with VAF &gt;49% were classified as presumptive MDS-bi TP53. Of the 157 cases with 1 TP53mut VAF ≤49%, 17 confirmed to have an intact wild-type TP53 copy and were classified as monoallelic. While 140 (89%) cases did not have copy number variation (CNV) analysis. We next evaluated the number of TP53mut cases classified differently by WHO and ICC. As WHO does not recognize TP53mut AML as a separate entity, 157 (29%) TP53mut AML were not classifiable. 46% (174/379) of the TP53mut MDS including 48 (30%), 12 (19%) and 79 (65%) of bi TP53, presumptive bi TP53 and monoallelic TP53mut MDS according to WHO were classified differently by ICC ( Figure 1A). Discordance between the two classifications were predominantly driven by: (i) The difference in VAF cut-off. Sixty patients (11%) with TP53mut VAF &lt;10% were excluded from the ICC classification of TP53mut MN as it mandates TP53mut VAF cut-off ≥10%. 11 (18%) and 41 (68%) of these had bi TP53, monoallelic TP53mut MDS by WHO criteria while 8 (13%) had AML. Importantly, within the VAF &lt;10% cohort, median overall survival (OS) of 2 TP53mut or 1 TP53mut with 17p13.1 (hereafter 17p) deletion or complex karyotype (CK, n=30) was significantly poor compared to 1 TP53mut VAF &lt;10% (11.6 vs 32.4 months; P =0.002, Figure 1B), suggesting that ICC may underestimate the poor prognosis of multi-hit or multi-hit equivalent TP53mut MN with VAF &lt;10%. (ii) The difference in bone marrow blast cut-off. The underlying assumption by WHO is that prognosis of bi TP53mut MDS is poor irrespective of blast percentage category (0-9% vs 10-19%). In contrast, ICC considers that TP53mut MDS/AML (blasts 10-19%) is associated with poor prognosis irrespective of TP53 allelic status. Median OS of TP53mut MDS with 10-19% blasts was significantly poor compared to blast 0-9% (6.4 vs 11.6 months, P &lt;0.0001). Second, median OS of bi TP53mut was significantly poor than monoallelic TP53mut in MDS- blast 0-9% (10.1 vs 15.9 months; P =0.0001) but not in blasts 10-19% (6.8 vs 6.2 months; P =0.19). Hence, exclusion of monoallelic TP53mut MDS with blast 10-19% as TP53mut MN from the WHO classification may underestimate the poor prognosis. (iii) The difference in the definition of biallelic and multi-hit TP53 loss. 35 cases with 1 TP53mut VAF ≤49%, had 17p deletion but did not have CNV analysis to confirm the loss of TP53 locus and could not be classified further using WHO. ICC classified 18 (50%) of these cases as multi-hit. Median OS of 1 TP53mut VAF ≤49%, and 17p deletion on karyotype was significantly poor than 1 TP53mut (VAF ≤49%without 17p deletion on karyotype (6.4 vs 14.6 months, P =0.001). (iv) The difference in the definition of multi-hit equivalent. 32% (33/104) WHO defined monoallelic cases without available CNV data, were classified as multi-hit-equivalent by ICC as they harbored CK. However, WHO does not consider CK as presumptive evidence of bi TP53. Median OS of 1 TP53mut VAF ≤49% with CK was significantly poor compared to 1 TP53mut without CK (8.2 vs 26.9 months, P =0.0008). CONCLUSION: Our study provides evidence that poor prognosis of ‘multi-hit’ TP53 with VAF &lt;10% is underestimated by ICC. On the other hand, poor prognosis of monoallelic TP53 MDS with 10-19% blasts as well as 1 TP53mut VAF ≤49% in the presence of CK is underestimated by WHO. These data suggest that both classifications can be further refined.

7059 Background: TP53-mutated ( TP53mut) myeloid neoplasms (MN) are aggressive leukemia with poor survival. A subset of TP53mut MN is preceded by TP53mut CCUS that is conventionally considered to be high-risk premalignant condition, though evidence supporting the notion is lacking. We studied outcomes of TP53mut CCUS compared to TP53 wild-type ( TP53wt) CCUS. Methods: Mayo Clinic Molecular Hematology Database (N=7593) was queried to identify patients (pts) harboring pathogenic variant(s) in exons 4-11 of the TP53 gene with ≥2% variance allele frequency (VAF). CCUS was defined using the 5th edition of the WHO Classification for MN. Results: Of 457 pts with TP53mut, 29 (5.9%) had TP53mut CCUS. The median age at diagnosis was 67 years, 17 (59%) were female, and 20 (69%) had received cytotoxic therapies. One and ≥2 TP53mut were seen in 26 (89.6%) and 3 (10.3%) pts, respectively. Median TP53mut VAF was 9% (range 3-42), 3 had TP53mut VAF ≥20%, and 4 (14%) had non-MDS defining cytogenetic anomalies. Of 16 pts with available follow up evaluation (median interval 22 months, Table), 3 (10.3%) progressed to TP53mut MN at 5, 13, and 14 months from diagnosis. We next compared outcomes of TP53mut CCUS to TP53wt CCUS (n=138). The proportion of pts developing MN was not different between TP53wt and TP53mut CCUS (18.1 vs 10.3%, P= .42). Progression free survival of TP53mut CCUS was comparable to TP53wt CCUS at 1- (77 vs 83%), 2- (67 vs 67%), and 5-years (67 vs 59%, P=.9). Similarly, overall survival of TP53mut vs TP53wt CCUS at 1- (81 vs 89%), 2- (76 vs 76%), and 5-years (76 vs 67%) was comparable ( P= .94). Conclusions: In contrast to the prevalent notion, TP53mut was not associated with a higher risk of MN progression or mortality compared to TP53wt CCUS. Majority of TP53mut clones showed remarkable stability over years. [Table: see text]