Hiwase, Devendra

Abstract Allogeneic hematopoietic stem cell transplant (alloHCT) is considered for all patients with myeloid neoplasms (MNs) harboring TP53 mutations (TP53mut). The aim of this international study across 7 transplant centers in the United States and Australia was to identify factors associated with improved post-alloHCT survival. Of 134 TP53mut MN cases who underwent alloHCT, 80% harbored complex karyotype; 94% of TP53 variants were localized to the DNA-binding domain (DBD). Most common comutations were ASXL1 (7%), TET2 (7%), and DNMT3A (6%). Median post-HCT survival was 1.03 years, and overall survival (OS) at 1 year, 2 years, and 3 years was 51.4%, 35.1%, and 25.1%, respectively. A total of 103 cases (76.9%) met the International Consensus Classification (ICC) criteria for MN with mutated TP53 (referred to as ICC-defined TP53mut MN hereafter). The 3-year OS of ICC-defined TP53mut was significantly shorter compared with that of other TP53mut MNs (3-year OS, 16.9% vs 54.9%; P = .002). ICC-defined TP53mut MNs was independently associated with inferior OS (hazard ratio [HR], 2.62; P = .019). The presence of non-DBD TP53mut only (HR, 3.40; P = .005), DNMT3A comutation (HR, 2.64; P = .016), and pre-alloHCT bone marrow blasts ≥5% (HR, 2.76; P = .006) was independently associated with inferior relapse-free survival (RFS), whereas melphalan-based conditioning was associated with superior RFS (HR, 0.52; P = .005). Combining these variables, we constructed a hierarchical model that stratified patients into low-, intermediate-, and high-risk categories with 1-year RFS of 81.3%, 31.3%, and 6.7%, respectively (P < .001). In conclusion, a subset of MN harboring TP53mut who have low blasts pre-alloHCT and received melphalan-based conditioning derived long-term benefit from alloHCT.

Abstract This retrospective analysis aimed to provide evidence-based risk stratification of TP53-mutated (TP53mut) myeloid neoplasms (MNs). Of 580 MNs harboring TP53mut with variant allele frequency (VAF) ≥2%, 219 (37.8%), 194 (33.4%), 92 (15.9%), and 75 (12.9%) were classified as acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) with low blasts (MDS-LB), MDS with excess blasts (MDS-EB)-2, and -EB1 according to the revised fourth edition of the World Health Organization (WHO) classification, respectively. Hierarchical analysis identified the following 4 risk groups with distinct survival: (1) MDS-LB, (2) MDS-EB1/EB2/AML VAF <10%, (3) MDS-EB1/EB2 VAF ≥10%, and (4) AML VAF ≥10%. We next evaluated the impact of allelic status, VAF, and complex karyotype (CK). In our cohort, the significance of biallelic status was limited to MDS with <5% blasts and not for blasts 5% to 9%, as proposed by the International Consensus Classification (ICC), or 5% to 19%, as proposed by the fifth edition of the WHO (WHO-5). MDS-EB1 and -EB2 with VAF ≥10% had comparable survival (9.6 vs 7.2 months; P = .12), regardless of allelic status. Contrary to the ICC proposal, MDS-EB1/EB2 with VAF <10% and CK had poor survival compared with those without CK, comparable to MDS-EB1/EB2 with VAF ≥10% (5.6 vs 26.2 vs 6.3 months; P = .003). Survival of TP53mut AML was poor (median 3.9 months) regardless of allelic/CK status. Thus, using ICC or WHO-5 may underestimate prognosis of MDS with blasts 5% to 19% and 5% to 9%, respectively. Collectively, the hierarchical model acknowledges poor survival of 91.9% TP53mut MDS and AML compared with 36.5% and 80.7% by WHO-5 and ICC, respectively.

ABSTRACTA total of 142 patients with myeloproliferative neoplasms (MPNs) or acute myeloid leukemia (AML) associated with multihit TP53 mutations (mTP53 MUT) were accessed from the Mayo Clinic database and included (i) chronic phase MPN (MPN‐CP; N = 19), (ii) accelerated phase MPN (MPN‐AP; N = 14), (iii) blast phase MPN (MPN‐BP; N = 28), and (iv) AML (N = 81). Concurrent ASXL1 MUT, EZH2 MUT, IDH1,MUT and IDH2 MUT were more common in MPN‐MUTBP‐mTP53 compared to AML‐mTP53 MUT. At median of 11.6 months follow‐up, 124 (87%) deaths and 19 (13%) allogeneic stem cell transplantations (ASCT) were documented. Overall survival (OS), calculated from the time of mTP53 MUT detection, was similar between MPN‐BP‐mTP53 MUT (median 4.6 months) and MPN‐AP‐mTP53 MUT (5.6 months; p = 0.5) but both were inferior to MPN‐CP‐mTP53 MUT (11.6 months, p < 0.01). OS in MPN‐CP‐mTP53 MUT was similar to that of AML‐mTP53 MUT (median 7.4 months, p = 0.07). In multivariable analysis, OS was favorably affected by ASCT (HR 0.4, p = 0.03) and disease stage (i.e., chronic phase disease) or achieving response to pre‐transplant chemotherapy (HR 0.2, p < 0.01) and unfavorably by the presence of concurrent TET2 MUT or DNMT3A MUT (HR 2.7, p < 0.01). Based on these risk factors, a 3‐tiered risk model was constructed: low (no risk factors; N = 18; median OS 23.8 months); intermediate (one risk factor; N = 44; 11.1 months); and high (two or more risk factors; N = 80; 4 months; p < 0.01). The current study highlights the equally detrimental impact of mTP53 MUT on long‐term survival in MPN and AML and identifies predictors of short‐term survival.

ABSTRACT Alterations in the tumor suppressor gene TP53 are common in human cancers and are associated with an aggressive nature. Approximately 8%–12% of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) harbor TP53 mutations ( TP53 mut ) and present immense challenges due to inherent chemoresistance and poor outcomes. As TP53 mut are more common in older individuals and those with secondary/therapy‐related myeloid neoplasms (MN), their incidence is expected to increase with an aging population and rising proportion of cancer survivors. Treatments used for other MN—intensive chemotherapy, hypomethylating agents, and the BCL‐2 inhibitor venetoclax—do not improve the survival of TP53 mut MN patients meaningfully. Additionally, further development of many promising agents has been discontinued, highlighting the challenges. Widespread acknowledgment of these problems led to the recognition of TP53 mut MN as a distinct entity in the 5th edition of the World Health Organization and International Consensus Classifications. However, critical discrepancies between the two classifications may lead to under‐ or overestimation of the prognostic risk. Here, we review recent advances in the biology, diagnosis, and treatment of TP53 mut MN. The development of TP53 mut MN is positioned at the intersection of age, hereditary predisposition, and anti‐cancer therapies. Precursor TP53 mut clones can be detected years prior to the eventual leukemic transformation—raising the possibility of early intervention. We discuss the two classification systems and the bearing of the discrepancies between the two on timely and effective management. We provide novel evidence in the areas of discrepancies. Finally, we review the current therapeutic landscape and the obvious limitations of the currently used therapies.

ABSTRACT The clinical relevance of TP53 mutations ( TP53 MUT ) in myeloproliferative neoplasms (MPN) and their prognostic interaction with MPN subtype designation has not been systematically studied. In the current study, 114 patients with MPN harboring TP53 MUT (VAF ≥ 2%) were evaluated for overall survival (OS), calculated from the time of TP53 MUT detection: chronic phase myelofibrosis (MF‐CP; N = 61); blast‐phase (MPN‐BP; N = 31) or accelerated‐phase (MPN‐AP; N = 16) MPN, and polycythemia vera/essential thrombocythemia (PV/ET; N = 6). Sixty‐five (57%) patients harbored International Consensus Classification (ICC)‐defined multihit TP53 MUT and 56 (49%) monosomal/complex karyotype (MK/CK). Majority of MPN‐BP (90%) and MPN‐AP (81%) while 39% of MF‐CP and none of PV/ET patients harbored multihit TP53 MUT . OS in MPN‐BP and MPN‐AP was equally dismal (median 6 vs. 4.5 months, respectively; p = 1.0), regardless of multihit configuration ( p = 0.44), while OS in TP53 MUT MPN‐BP/AP ( N = 47; median 4 months) was inferior to that of a separate cohort ( N = 49) with TP53 wild‐type MPN‐BP/AP (median 11 months; p < 0.01). OS in MF‐CP was significantly shorter with multihit versus non‐multihit TP53 MUT (median 10 vs. 35 months; HR 2.9; p < 0.01), independent of other MF‐relevant genetic risk factors, including ASXL1/SRSF2/U2AF1 mutations. Multihit TP53 MUT was also associated with inferior survival following allogeneic stem cell transplant (ASCT): median 9 months versus “not reached” in patients with ( N = 9) versus without ( N = 8) multihit TP53 MUT ( p < 0.01). The presence of multihit or non‐multihit TP53 MUT in MPN‐BP/AP or multihit TP53 MUT in MF‐CP is associated with exceptionally poor prognosis and justifies inclusion into the ICC category of “myeloid neoplasms with mutated TP53 .” By contrast, detection of non‐multihit TP53 MUT , by itself, might not endanger short‐term survival in MF‐CP, PV, or ET.

Introduction The International Prognostic Scoring System (IPSS) and its revised version (IPSS-R) were developed using datasets from patients (pts) with untreated MDS. The cytogenetic risk groups used in IPSS-R were expanded to 5 groups from the 3 used in IPSS. Among the new groups introduced in IPSS-R is the “very complex” karyotype (VCK) where ≥4 karyotypic abnormalities are seen compared to “complex karyotype (CK)” with only 3 abnormalities. However, the prognostic impact of VCK vs CK, as well as individual cytogenetic abnormalities and TP53 mutation (TP53mut) status within the CK and VCK subgroups in pts with MDS treated with hypomethylating agents (HMAs) has not been well studied. Hence, we analyzed these questions in a large cohort of HMA-treated MDS pts in the icMDS VALIDATE database. Methods The icMDS VALIDATE database contains MDS pts treated with frontline HMA monotherapy or HMA-based combinations from 22 specialized international centers. Pts with unknown HMA type, date of HMA initiation, missing age, missing sex, missing cytogenetic data, bone marrow or peripheral blood blasts ≥20%, or missing survival status were excluded. We performed time-to-event analyses using the Kaplan-Meier method and compared groups by the log-rank test. We measured overall survival (OS) from time of HMA initiation. VALIDATE protocol was exempted, acknowledged, or approved by all centers' IRBs. VALIDATE is supported by an independent grant from Abbvie. Results A total of 1940 pts were included. Median age was 70 (range: 18-99) years and 66% were men. According to IPSS-R cytogenetic risk groups, 1.9% (37) were very good, 43.4% (841) good, 15.5% (301) intermediate, 11.6% (226) poor, and 27.6% (535) very poor. By HMA type, 71% of pts were treated with azacitidine, 14% with decitabine, 6% with HMA and venetoclax, and 9% with another HMA combination. Approximately 28% of pts underwent allogeneic hematopoietic stem cell transplant (alloHSCT). The IPSS-R cytogenetic risk groups had different OS (p&lt;0.001)with median OS (mOS; months [mo], 95% CI) as follows: very good (43.4, 34.7-72.5), good (41.7, 36.4-46.8), intermediate (24.5, 23.1-32.4), poor (24.2, 19.2-28.5), and very poor (13.6, 12.5-14.5). The difference remained significant (p=0.001) after censoring at time of alloHSCT with mOS as follows: very good (40.4, 23.2-64.3), good (24.3, 22.2-26.3), intermediate (19.3, 15.1-22.2), poor (12.2, 10.3-14.8), and very poor (9.1, 8.2-19.7). Interestingly, the difference between mOS for intermediate and poor risk cytogenetics became more apparent after censoring at time of alloHSCT. Next, we compared the outcomes of pts with CK and VCK to non-complex karyotype (NCK) MDS. The mOS for pts with VCK MDS (13.6 mo, 12.5-14.5) was worse compared to pts with CK (19.9 mo, 19.9-16.8; p=0.004) and NCK (36.1 mo, 32.7-37.8; p&lt;0.001) MDS. Among the 1458 pts with available molecular data, more pts with VCK (75%, 330) MDS had a concurrent TP53mut compared to pts with CK (40%, 21; p&lt;0.001) and NCK (7%, 64 p&lt;0.001) MDS. Considering only patients with TP53mut MDS, mOS for pts with VCK (12.2, 11.1-13.9) was worse compared with NCK (24.2, 16-1-53.1; p&lt;0.001) but not with CK (19.9, 9.5-NR; p=0.9); the difference between CK and NCK was not significant (p=0.16). Among pts with TP53 wildtype (TP53WT) MDS, VCK (15.0, 13.2-18.2) had a similar mOS to TP53WT CK (18.8, 12.6-41.1; p=0.19) while both groups had worse mOS compared to TP53WT NCK (33.4, 30.1-37.0) (p=0.01). In a survival analysis of 616 pts with MDS with ≥3 cytogenetic abnormalities, -17/del(17p) (12.8 mo; p=0.009), inv(3)/t(3q)/del(3q) (10.9 mo; p=0.006), and del(7q) (12.1mo; p=0.024), though not -7 (12.6mo; p=0.23), were associated with lower mOS compared to the pts with MDS without these abnormalities (14.3mo). Conclusions Using one of the largest databases of HMA-treated MDS pts, we show that IPSS-R cytogenetic risk categories associate with significantly different survivals among HMA-treated MDS pts, even after censoring at time of alloHSCT. Importantly, VCK MDS was associated with worse mOS compared to CK and NCK MDS but not in pts with a concurrent TP53mut. Among pts with MDS with ≥3 chromosomal abnormalities, having -17/del(17p), inv(3)/t(3q)/del(3q), or del(7q) was associated with worse survival.

Background: TP53-mutated (TP53mut) myeloid neoplasms (MN) have particularly poor survival. Discrepancies in defining TP53mut MN have impact on diagnostic work up, therapeutic decisions, and clinical trial enrolment. Methods: MN cases harboring TP53mut (variant allele frequency, VAF ≥2%) were classified based on bone marrow (BM) and peripheral blood (PB) blast % using the 4th revision of the WHO classification (WHO-4R). Biallelic loss was defined as (i) ≥2 mutations each with VAF ≥2%; (ii) single TP53mut VAF ≥2% plus 17p loss detected on karyotype, FISH, or SNP; or (iii) single TP53mut VAF ≥50%, whereas monoallelic loss was defined as single TP53mut VAF &lt;50% without 17p loss. Primary endpoint was overall survival (OS) from diagnosis. Conditional Inference Trees (CIT) analysis was used to determine the true effect of a predictor. Results: We identified 580 cases including WHO-4R defined acute myeloid leukemia (AML, BM/PB blasts ≥20%, n=219, 37.8%), myelodysplastic syndrome (MDS) with excess blasts-2 (EB-2, BM 10-19% or PB 5%-19%, n=92, 15.9%), MDS with excess blasts-1 (EB-1, BM 5-9% or PB 2-4%, n=75, 12.9%), and the remaining were MDS with low blasts (-LB, BM &lt;5% and PB ≤1%, n=194, 33.4%). Of the 578 cases evaluable for allelic status, 437 (75.6%) and 141 (24.4%) had biallelic and monoallelic TP53 loss, respectively. Higher frequency of biallelic loss was observed with increasing blasts. 63.2%, 73.3%, 78% and 86.3% of cases with MDS-LB, MDS-EB1, MDS-EB2, and AML had bi-allelic TP53 loss (P&lt;0.0001). In a multivariable analysis, WHO-4R categories, VAF ≥10%, and biallelic loss were independent predictors of poor survival. CIT analysis further stratified the cohort into 4 groups with distinct survival: (1) MDS-LB (n=194, 33.4%); (2) MDS-EB1/EB2 and AML with VAF &lt;10% (n=38, 6.6%); (3) MDS-EB1/EB2 with VAF ≥10% (n=149, 25.7%); and (4) AML with VAF ≥10% (n=199, 34.3%). MDS-LB cases could be further stratified based on allelic status and complex karyotype (CK): OS was poor for cases with biallelic TP53 loss and monoallelic TP53mut with CK compared to monoallelic TP53mut without CK, who had the most favorable survival (12.7 vs. 13 vs. 34.8 months, P&lt;0.0001).MDS-EB1/EB2/AML with VAF&lt;10% could also be stratified by CK: MDS-EB1/EB2/AML with VAF&lt;10% cases without CK had the favorable survival compared to their counterparts with CK and MDS-EB1/EB2 with VAF ≥10% cases (26.2 vs. 5.6 vs. 6.3 months, P=0.003).MDS-EB1/EB2 with VAF ≥10% was a homogenous subgroup: Biological characteristics including the proportion of cases with biallelic TP53 loss, CK (P&gt;0.9), monosomal karyotype (MK, P&gt;0.9), del 5q (P=0.6), del 7q (P=0.4), and del 17p (P=0.2) were comparable between MDS-EB1 and -EB2 with VAF ≥10%. Importantly, median OS of MDS-EB1 and EB2 with VAF ≥10% was comparable (9.6 vs. 7.2 months, P=0.12). OS in this group was comparable regardless of the blast %, allelic status, or presence of CK.AML with VAF ≥10% had extremely poor survival: Median OS was 3.9 months. Survival of AML was equally poor irrespective of the mono- or biallelic (3.6 vs. 3.9, P=0.89) and non-CK vs. CK (1.8 vs. 3.9 months, P=0.09). Combined, our model would acknowledge poor survival of 514 (89.1%) cases. In contrast, retrospective application of the 5th edition of the WHO classification (WHO-5) and International Consensus Classification (ICC) would classify only 211 (36.4%) and 468 (80.7%) cases as biallelic/multi-hit TP53mut MN, respectively. Finally, the Harrell's c-index of the proposed model, WHO-5, and ICC was 0.66, 0.571, and 0.617, respectively. Conclusion: We provide evidence for subsequent refinements in classifying MN harboring TP53mut. Our salient findings include: (i) acknowledgement of CK as ‘biallelic equivalent’ in MDS-LB; as well as EB1/EB2/AML with VAF 2 to &lt;10% cases; and (ii) demonstration of poor survival of MDS-EB1 and -EB2 with VAF ≥10% regardless of the allelic status. In conclusion, our proposed model acknowledged poor survival of a higher proportion of cases as TP53mut MN compared to the current models with a higher c- index.

Background The prognostic relevance of TP53 mutations (TP53MT) in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) has been extensively studied and the information accessed for defining the new International Consensus Classification (ICC) category of “myeloid neoplasms with mutated TP53” (Blood 2022;140:1200). The latter designation requires ≥10% TP53 variant allele frequency (VAF) for AML and MDS/AML and in case of MDS, multi-hit TP53 or ≥10% VAF associated with complex karyotype (CK). We examined the prognostic relevance of TP53MT in myeloproliferative neoplasms (MPN), specified by subtype and disease stage. Methods The current study was conducted under an institutional review board approved minimum risk protocol. Additional informative cases from the University of Florence, Italy and the South Australian Myeloid Neoplasm Registry were included. Diagnostic criteria and assignment of TP53 allelic state were according to the ICC. Next-generation sequencing (NGS) and cytogenetic studies were performed according to institutional standard protocols. Conventional statistical methods were employed. Survival analyses were censored for allogeneic stem cell transplantation (ASCT) and were calculated from the time of first detection of TP53MT. Results 115 patients with MPN and documented pathogenic TP53MT were considered (median age 68.5 years). ICC-defined subtype designations, at time of TP53MT detection, were polycythemia vera (PV) or essential thrombocythemia (ET) (N=9), chronic phase myelofibrosis (MF-CP; N=63), accelerated phase MPN (MPN-AP; N=16), and blast phase MPN (MPN-BP; N=27). Driver mutation distribution was JAK2 64%, CALR 18%, MPL 8%, and triple-negative 10%. Karyotype was monosomal (MK) in 42%, CK 9%, and normal (NK) 35%. Frequent co-mutations were ASXL1 (28%), TET2 (14%), and SRSF2 (14%). TP53MT were classified as ICC-defined multihit in 67 (58%) cases; karyotype in the latter was MK (58%), CK (16%), non-MK/CK (13%), or NK (13%). TP53 VAF was ≥50% in 27 (24%) patients and &lt;10% in 25 (22%). TP53MT included one (N=96) or ≥2 (N=19). MPN subtype- and stage-specific distributions for multihit TP53MT were 91% for MPN-BP, 88% MPN-AP, 44% MF-CP, and 0% ET/PV. In order to examine disease subtype- and stage-specific prognostic contribution of TP53MT, the study population was divided into 10 operational groups: 1) PV/ET non-multihit/non-MK/CK (N=8; VAF range 3-32%); 2) MF-CP non-multihit/non-MK/CK with TP53MT VAF &lt;10% (N=10); 3) MF-CP non-multihit VAF ≥10% and non-MK/CK (N=11); 4) PV/ET/MF-CP non-multihit with MK/CK (N=5); 5) MF-CP multihit/non-MK/CK (N=8); 6) MF-CP multihit and MK/CK (N=20); 7) MPN-BP/AP non-multihit/non-MK/CK (N=2); 8) MPN-BP/AP non-multihit with MK/CK (N=2); 9) MPN-BP/AP multihit/non-MK/CK (N=9); and 10) MPN-BP/AP multihit with MK/CK (N=30). The corresponding median survivals were “not reached”, 55, 42, 6, 18, 10, “not reached”, 4, 4, and 6 months (p&lt;0.01). Survival was similar between groups 1, 2, and 3 (p&gt;0.2 for all comparisons) now referred to as “PV/ET/MF-CP non-multihit/non-MK/CK (N=39)”. Survival was similarly dismal for groups 8, 9, and 10 (p values &gt; 0.3 for all comparisons) now referred to as “MPN-BP/AP with or without multihit TP53MT or MK/CK (N=43)”. Survival was also similar between groups 4, 5, and 6 (p values &gt;3 for all comparisons) now referred to as “PV/ET/MF-CP with multihit TP53MT or MK/CK (N=33)”. The three consolidated groups were subsequently compared for survival that showed a significantly worse outcome for “MPN-BP/AP with or without multihit TP53MT or MK/CK” with median survival of 4 months, compared to 12 months for “PV/ET/MF-CP with multihit TP53MT or MK/CK” (HR 2.3; 95% CI; 1.3-3.9) and 55 months for “PV/ET/MF-CP non-multihit/non-MK/CK” (10.9; 95% CI 5.3-22.4); survival in the latter two groups was also significantly different, in favor of PV/ET/MF-CP non-multihit/non-MK/CK (HR 4.8; 95% CI 2.3-10.1). Conclusions: The presence of multi-hit TP53MT or MK/CK, in MF-CP, and possibly in ET/PV, warrants their inclusion in the ICC category of “myeloid neoplasms with mutated TP53”. By contrast, non-multihit TP53MT in ET/PV/MF-CP, regardless of VAF and in the absence of MK/CK, does not appear to compromise short-term survival. The observations from the current study also suggest a prognostic hierarchy with blast percentage being the most unfavorable, followed by MK/CK and multihit TP53MT.

Introduction: Response assessment is used to evaluate effectiveness of hypomethylating agent (HMA)-based therapy in myelodysplastic syndromes/neoplasms (MDS) in clinical practice and trials. Recently, the clinical response criteria (IWG 2023) and the clinical-molecular risk assessment (IPSS-M) in MDS were published. However, it remains unknown whether the IWG 2023 response criteria have an independent impact on overall survival (OS) when adjusting for baseline IPSS-M risk. Additionally, the association of IWG 2023 response criteria with OS in patients (pts) undergoing allogeneic stem cell transplantation (allo-HCT) versus those who do not is unknown. Lastly, it is unclear if optimal time-to-transplant impacts OS in MDS pts who achieve a IWG 2023 defined remission with HMA therapy. We examined these questions in a large population of MDS pts within the multi-institutional international consortium for MDS (icMDS) VALIDATE database. Methods: High-risk MDS pts with IPSS ≥1.5 or IPSS-R &gt;3.5 treated with HMA-based therapy were included in the study. Baseline IPSS-M risk was stratified into very low/low/moderate low (VL+L+ML), moderate-high/high (MH+H), and very high (VH). Response to treatment was evaluated using the IWG 2023 criteria and grouped into: composite complete response (cCR) and no cCR. cCR included: complete response (CR), CR equivalent (CRequ), CR bilineage (CRbi), CR unilineage (CRuni), and CR with partial hematologic recovery (CRh). We analyzed the differential impact of achieving cCR on HMA-based therapy prior to transplant on OS in pts who either did or did not undergo allo-HCT, while adjusting for their baseline IPSS-M risk in Cox regression analysis. Optimal time-to-transplant was determined based on age and IPSS-M category as described by Tentori et al. (JCO 2024). Pts proceeding to allo-HCT were stratified on whether they underwent transplant within the optimal time-to-transplant timeframe after MDS diagnosis or not. VALIDATE protocol was exempted, acknowledged, or approved by all centers' IRBs. VALIDATE is supported by an independent grant from AbbVie. Results: We analyzed 762 MDS pts. The median age at MDS diagnosis was 68 years (range: 19-95 years) and 64% of pts were male. Distribution of the baseline IPSS-M risk was: VL+L+ML in 110 (14%) pts, MH+H in 347 (46%) pts, VH in 305 (40%) pts. Pts received azacitidine monotherapy, decitabine monotherapy, and HMA-based combination therapy (e.g. HMA + venetoclax) in 52%, 21%, and 28% of cases, respectively. A total of 282/762 (37%) pts achieved cCR as their best response to HMA-based therapy. The median OS for all pts was 18.7 months (95% CI: 16.6-21.3 months). Pts who did not undergo allo-HCT (n=436, 57%) had an improved median OS if they achieved cCR when compared to pts in the no cCR group in all IPSS-M risk groups (VL+L+ML: 23.5 months vs. 10.7 months; MH+H: 20.8 months vs. 11.6 months; VH: 13.8 months vs. 7.5 months). Cox analysis demonstrated an independent effect of cCR on OS in these pts when adjusted for baseline IPSS-M risk (cCR vs. no cCR: HR 0.60, 95% CI 0.48-0.76, p&lt;0.001). In contrast, in pts who subsequently received an allo-HCT (n=326, 43%), achieving cCR with HMA prior to allo-HCT did not provide an additional OS benefit, when adjusted for baseline IPSS-M risk (cCR vs. no cCR: HR 1.00, 95% CI 0.73-1.38, p=0.986). The median time-to-transplant was 6.7 months and 34% of transplanted MDS pts received their allo-HCT during the optimal timeframe. Among pts who achieved cCR with HMA-based therapy prior to allo-HCT, optimal time-to-transplant was associated with significantly improved OS (optimal vs. non-optimal timing: HR 0.55; p=0.033). Conclusion: Baseline IPSS-M risk and allo-HCT had an independent impact on OS, while IWG 2023 defined cCR had an independent effect on OS only in non-transplanted MDS pts. While this retrospective analysis occurred at large academic centers with specific expertise in the management of MDS, our data may have an impact on clinical practice: (i) failure to achieve cCR on HMA therapy prior to transplant should not impact the decision to proceed to allo-HCT, (ii) upfront allo-HCT without prior HMA therapy might also be an option if the clinical situation and availability of donors allow, and (iii) allo-HCT should ideally be performed during the timeframe that is considered optimal as defined by pt age and baseline IPSS-M.

Background: TP53 mutations (TP53mut) are highly prevalent in therapy-related myeloid neoplasms (t-MN) compared to de novo MN (35-40% vs 7-13%) and are associated with a poor outcome. Understanding the risk factors involved in the pathogenesis of TP53mut t-MN is critical to prevent its development. Methods: We characterized t-MN cases by examining primary cancer type vs autoimmune disease diagnosis vs solid organ transplantation, treatment modality, and latency (interval between primary cancer/disease and t-MN diagnosis) to identify patient and disease-related factors associated with TP53mut t-MN. Allelic loss of TP53mut MN was defined according to International Consensus Classification (ICC) criteria (Arber et al., Blood 2022). Results: Of 587 t-MN patients, 33% (n=194) had acute myeloid leukemia (t-AML) and 67% (n=393) had myelodysplastic syndrome (t-MDS, blasts&lt;20%). Primary diagnosis comprised of 243 (41.6%) solid cancers and 300 (51.4%) hematological malignancies, while 7% (n=41) of t-MN cases had autoimmune disease or underwent solid organ transplant. Overall, 94 (16.1%) patients received prior radiotherapy (RT) alone and 75.6% (n=444) received chemotherapy (CT) with/without RT. 109 patients (18.7%) underwent autologous stem cell transplant (ASCT). The median latency from primary diagnosis to t-MN was 83.2 months (IQR 41.3, 153.2), and there was a trend towards shorter latency in t-AML compared to t-MDS (70.5 vs 85.8 months; P=0.07). Of the t-MN patients, 280 (47.7%) harbored TP53mut, which was associated with significantly poorer survival compared to wild-type (TP53wt) t-MN (9.7 vs 21.9 months; P &lt;0.001). In contrast to TP53wt (59.0% vs 41.0%), the majority of TP53mut t-MN presented with t-MDS vs t-AML (75.7% vs 24.3%; P &lt;0.001). According to ICC criteria, multi-hit MDS (n=131; 47.8%) was the most common entity, followed by AML (n=68; 24.8%), MDS/AML (n=34; 12.4%), and single-hit MDS (n=8, 2.9%). Poor prognostic karyotype changes e.g., del 5q, del 7q, complex karyotype and monosomal karyotype, were more prevalent in TP53mut compared to TP53wt t-MN. Co-mutations in other genes were enriched in TP53wt t-MN. As TP53mut t-MN is associated with a dismal outcome, we assessed the factors associated with its development. There were no significant differences in median age at primary cancer/disease diagnosis (59.0 vs 59.9 years; P=0.4) or gender (females 43.3% vs 39.3%; P=0.3) between TP53mut and TP53wt t-MN. However, TP53mut patients were older at t-MN diagnosis (69 vs 67.4 years; P=0.05). Correlations between gene mutations and prior malignancies revealed a significant association between TP53mut and hematological primary cancers (odds ratio [OR] 1.6; P=0.006), especially multiple myeloma (MM, OR 4.9; P&lt;0.001) and lymphoproliferative disease (LPD, OR 2.0; P=0.013). Among solid cancers, head and neck malignancies were significantly associated with increased risk of developing TP53mut t-MN (OR 7.7; P=0.01). Compared to RT alone, ASCT (OR 2.2; P=0.004) and CT (OR 2.0; P=0.008) were associated with an increased risk of TP53mut t-MN. Recent studies indicate that CT/RT confer a selective advantage to preexisting TP53mut hematopoietic stem and progenitor cells, allowing clonal expansion/evolution and progression to t-MN. We hypothesized that TP53mut t-MN with high-risk disease features is a function of TP53mut clonal expansion/evolution rate and would predict latency between primary cancer and t-MN. Indeed, the latency between primary cancer and t-MN diagnosis was longer in TP53mut (87.8 months, IQR 45.5, 154.1) compared to TP53wt (74.7 months, IQR 37.5, 146.9 months) t-MN (P=0.05). Interestingly, 54% and 29% of TP53mut t-MN had a latency of ≥5 and ≥10 years, respectively. There were no correlations between latency and TP53 variant allele frequency (VAF) (r=0.38 and P=0.7) or between TP53mut t-MDS and t-AML (85.2 vs 109.3 months; P=0.9). Together, latency between primary cancer and t-MN was not associated with TP53mut t-MN phenotype, VAF or other poor-risk disease features. Conclusion: Hematological malignancies, especially MM and LPD treated with high-dose CT, were strongly associated with TP53mut t-MN development, highlighting the importance of careful and ongoing screening in this population. Also, the long latency of TP53mut t-MN provides an opportunity to devise effective surveillance strategies and preventative interventions long before TP53mut t-MN development.