Transplant-associated thrombotic microangiopathy (TA-TMA) is an endothelial dysfunction syndrome observed after allogeneic hematopoietic cell transplant (alloHCT). Our aim was to externally validate the impact of high-risk features on the clinical outcomes of adult patients meeting the updated TA-TMA harmonizing criteria. Between 2005 and 2022, 99 patients were diagnosed with TA-TMA at Mayo Clinic Rochester (incidence 6.2%) after a median of 137 days post alloHCT (IQR: 34-283 days). The development of TA-TMA was associated with an inferior overall survival posttransplant (HR: 3.8, 95% CI: 2.97-4.72). High-risk features, including concomitant infection, acute graft-versus-host disease (GVHD), and organ dysfunction, were associated with poor survival, while LDH elevation was not associated with inferior outcomes. The most common treatment strategy for TA-TMA was discontinuation of calcineurin or mTOR inhibitors in 80 (81%) patients. Thirty (37.5%) patients experienced worsening of GVHD with this strategy, of which 26 (86.7%) patients had died at last follow-up. The most common cause of death among these patients was worsening GVHD (69%; n = 18), followed by infection (11%; n = 3), disease relapse (8%; n = 2), other/unknown causes (8%; n = 2), or TA-TMA (4%; n = 1). Objective response rate (ORR) to initial treatment for the cohort was 56.6%. Eculizumab was used in 11 patients with an observed ORR of 70%, including 5 complete responses. In conclusion, TA-TMA remains a significant contributor to non-relapse mortality and is associated with worse survival following alloHCT. Not all high-risk features, particularly LDH elevation, have consistently demonstrated a negative impact in adult cohorts. Patients with TA-TMA may benefit from immune suppression dose adjustment, rather than a discontinuation, and the addition of complement-directed therapy, particularly among high-risk patients.

PURPOSE BRAF and MEK inhibitors are standard treatments in histiocytic disorders, such as Erdheim-Chester disease (ECD). Some patients lack MAPK-pathway alterations, making these treatments less effective. METHODS We describe three patients with histiocytic disorders who have novel non-MAPK pathway alterations. These alterations were studied through genomic and in silico analyses when applicable, then treated with off-label medications rationally selected on the basis of genomic alterations. RESULTS Patient 1 had rapidly progressive ECD involving the CNS. A CSF1R in-frame deletion (p.S560_P566del) was identified, and in silico modeling predicted a gain-of-function mutation. This alteration was targeted with pexidartinib, which led to a clinical complete response (CR) within 2 months, and a partial response (PR) on imaging after 3 months. After 15 months, the disease became resistant to pexidartinib and transformed to histiocytic sarcoma. Patient 2 has skin-only involvement of a xanthogranuloma disorder. A KIF5B-FGFR1 fusion was identified on RNA sequencing and targeted with pemigatinib. At 24 months of follow-up, she remains in a clinical PR. Patient 3 has ECD involving the bone marrow, gastrointestinal tract, and subcutaneous tissues. A MEF2C-FLT3 fusion was identified and targeted with sorafenib. He achieved a clinical CR and radiographic PR within 3 months, which has continued for 30 months. CONCLUSION We report three patients with histiocytic disorders harboring novel alterations who had sustained responses to off-label kinase inhibitors specific to their histiocytic disorder. Pathogenic variants outside of the MAPK pathway, including variants of unknown significant, may be targeted with readily available small molecules.

In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

OBJECTIVES:Understanding of histiocytic disorders has been revolutionized by demonstration of mitogen-activated protein kinase (MAPK) pathway mutations, most commonly BRAFV600E. The optimal testing strategy to assess BRAFV600E is unknown. We aimed to compare performance of testing modalities, to propose a framework for evaluation of BRAFV600E mutation status in histiocytic disorders.METHODS:We retrospectively reviewed patients with histiocytic disorders and BRAF mutation testing on a lesional tissue specimen.RESULTS:In 120 patients, BRAF assessment included immunohistochemistry (IHC) in 97 (80.2%), polymerase chain reaction (PCR) in 35 (28.9%), and next-generation sequencing (NGS) in 62 (51.2%). Forty-five underwent both NGS and IHC. With NGS as the gold standard, the sensitivity and specificity of IHC were 82.4% and 96.4%. Three false negatives were observed in biopsy specimens with low BRAFV600E variant allele frequency or decalcified tissue. One false-positive IHC was observed in a lung biopsy specimen, likely due to antibody cross-reactivity with respiratory cilia. Among 14 with successful NGS and PCR, a single discordance was observed. Two PCR-to-IHC discrepancies were observed, including one other false-positive IHC.CONCLUSIONS:Immunohistochemistry was highly specific for detection of BRAFV600E. Main caveats were false negatives and lack of detection of non-BRAFV600E mutations. We propose the use of IHC as initial screening in general practice with reflex molecular testing if negative.

IntroductionThe survival of patients with metastatic renal cell carcinoma (mRCC) has improved dramatically due to novel systemic treatments. However, mRCC mortality continues to rise in Latin America.MethodsA retrospective, multicenter study of patients diagnosed with mRCC between 2010-2018 in Mexico City was conducted. The aim of the study was to evaluate the impact of healthcare insurance on access to treatment and survival in patients with mRCC.ResultsAmong 924 patients, 55.4%, 42.6%, and 1.9% had no insurance (NI), social security, (SS) and private insurance (PI), respectively. De novo metastatic disease was more common in NI patients (70.9%) compared to SS (47.2%) and PI (55.6%) patients (p<0.001). According to IMDC Prognostic Index, 20.2% were classified as favorable, 49% as intermediate, and 30.8% as poor-risk disease. Access to systemic treatment differed by healthcare insurance: 36.1%, 99.5%, and 100% for the NI, SS, and PI patients, respectively (p<0.001). NI patients received fewer lines of treatment, with 24.8% receiving only one line of treatment (p<0.001). Median overall survival (OS) was 13.9 months for NI, 98.9 months for SS, and 147.6 months for NI patients (p<0.001). In multivariate analysis, NI status, brain metastases, sarcomatoid features, bone metastases, no treatment were significantly associated with worse OS.ConclusionOS in mRCC was affected by insurance availability in this resource-limited cohort of Mexican patients. These results underscore the need for effective strategies to achieve equitable healthcare access in an era of effective, yet costly systemic treatments.

Book Citations: Authors, Title, HemaSphere, 2023;7(S3):pages. The individual abstract DOIs can be found at https://journals.lww.com/hemasphere/pages/default.aspx. Disclaimer: Articles published in the journal HemaSphere exclusively reflect the opinions of the authors. The authors are responsible for all content in their abstracts including accuracy of the facts, statements, citing resources, etc. 2125 their disease course, 7 and 13 of whom had MAPK pathway mutations and available response assessment at time of data cutoff, respectively. Overall response rate was 92.3% (PR n=9, CR n=3). Noticeably, all patients achieving a CR had a demonstrated MAPK pathway mutation, while the only non-responder did not. After a median follow up of 50 months (95%CI 34-66 months), 3 patient deaths had been observed with one patient development therapy-related AML. Summary/Conclusion: Neurologic RDD is rare and can involve a wide variety of structures within the cranium and spine, causing significant symptomatology. Targeted therapy with MEK inhibitor appears promising in these cases HemaSphere | 2023;7(S3) EHA2023 Hybrid Congress Copyright Information: (Online) ISSN: 2572-9241 © 2023 the Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Hematology Association. This is an open access Abstract Book distributed under the Attribution-NonCommercial-NoDerivs (CC BY-NC-ND) which allows third parties to download the articles and share them with others as long as they credit the author and the Abstract Book, but they cannot change the content in any way or use them commercially. Abstract Book Citations: Authors, Title, HemaSphere, 2023;7(S3):pages. The individual abstract DOIs can be found at https://journals.lww.com/hemasphere/pages/default.aspx.Book Citations: Authors, Title, HemaSphere, 2023;7(S3):pages. The individual abstract DOIs can be found at https://journals.lww.com/hemasphere/pages/default.aspx. Disclaimer: Articles published in the journal HemaSphere exclusively reflect the opinions of the authors. The authors are responsible for all content in their abstracts including accuracy of the facts, statements, citing resources, etc. 2126

Purpose: To evaluate the clinical presentation, treatment, and outcomes in adult patients with histiocytic disorders with ocular, orbital, optic nerve, or cavernous sinus involvement. Design: Observational, retrospective chart review. Participants: Adult patients (age > 18 years) at Mayo Clinic from January 1, 1996, to July 1, 2021, with histiocytic disorders. Inclusion criteria were (1) histiocytic disorder by biopsy and appropriate clinical phenotype; (2) available medical records; and (3) ocular, orbital, optic nerve, or cavernous sinus involvement. Methods: Retrospective chart review. Main Outcome Measures: Response to therapy, measured in clinical and radiographic impact. Results: Thirty-two patients were identified: 7 with Langerhans cell histiocytosis (LCH); 15 with ErdheimChester disease (ECD); 1 with mixed LCH/ECD phenotype; 8 with Rosai-Dorfman disease (RDD); and 1 with mixed RDD/ECD phenotype. Ophthalmologic involvement was part of the initial presentation in 69% of patients (22/32). Eyelid edema (13/32, 41%) and proptosis (12/32, 38%) were the most frequent presentations. Isolated orbital or cavernous sinus involvement was present in 3 of 7 patients with LCH and 1 of 8 patients with RDD. Optic nerve sheath involvement was present in 2 of 7 LCH patients, 14 of 15 ECD patients, and 1 RDD/ECD patient. Diffuse (> 75%) orbital involvement was seen in 12 of 15 ECD patients and 1 of 7 LCH patients. Ocular involvement was seen in 1 of 15 ECD patients, 6 of 8 RDD patients, and 1 of 1 mixed RDD/ECD patient. The cavernous sinuses were involved in 1 of 7 LCH patients, 5 of 15 ECD patients, and both mixed phenotype patients. Visual acuity was affected in 14 patients (14/24, 58%) with a median logarithm of the minimum angle of resolution visual acuity of 0.1 (range, -0.12 to 3). BRAF V600E mutations were found in 75% (3/4) of LCH patients and 91% (10/11) of ECD patients. Patients received a variety of treatment, and response was variable across disease types. Conclusions: Orbital involvement was more commonly seen in LCH and ECD, whereas ocular involvement was more common in RDD. Visual acuity may be impacted from ocular involvement or compression of the optic nerve with diffuse orbital involvement. Ophthalmology 2023;130:77-86 (c) 2022 by the American Academy of Ophthalmology

Eculizumab is effective for complement-mediated thrombotic microangiopathy (CM-TMA), also known as atypical hemolytic uremic syndrome. Although lifelong therapy had been suggested, discontinuation does not universally lead to relapse. Comprehensive data evaluating risk factors for recurrence following discontinuation are limited. Our aim was to systematically review available literature assessing the role of complement genetic variants in this setting. Reports on CM-TMA and eculizumab withdrawal published before 1 January 2021, were included. Key reasons for patient exclusion were no follow-up after drug withdrawal and patients lacking complement genetic testing. Two-hundred eighty patients from 40 publications were included. Median age was 28 years, and 25 patients had a known history of renal transplant. Complement genetic variants were identified in 60%, most commonly in CFH (n = 59) and MCP/CD46 (n = 38). Of patients with a complement gene variant, 51.3% had >= 1 likely pathogenic/pathogenic variant whereas the remaining had variants of uncertain significance (VUS). Overall relapse rate after therapy discontinuation was 29.6%. Relapse rate was highest among patients with CFH variants and MCP/CD46 variants in canonical splice regions. VUS (P < .001) and likely pathogenic/pathogenic variants (P < .001) were associated with increased relapse. Presence of a renal allograft (P = .009); decreasing age (P = .029); and detection of variants in CFH (P < .001), MCP/CD46 (P < .001), or C3 (P < .001) were all independently associated with relapse after eculizumab discontinuation. Eculizumab discontinuation is appropriate in specific patients with CM-TMA. Caution should be exerted when attempting such a strategy in patients with high risk of recurrence, including a subgroup of patients with MCP/CD46 variants.

Advances in the treatment of Langerhans cell histiocytosis (LCH) have resulted in a growing survivor population. There is a lack of data on long-term outcomes among adults with LCH. We conducted a retrospective record review of 219 adults (aged ≥18 years) with LCH. Most common presentation was multisystem (34.2%), followed by single-system pulmonary (32%), unifocal (28.3%), and single-system multifocal (5.5%) LCH. Risk organ involvement (the liver, spleen, or bone marrow) was seen in 8.7% of cases, and 40 of 88 (45.5%) tested cases were BRAFV600E. At a median follow-up of 74 months, 5-year progression-free survival (PFS) was 58.3% and estimated median PFS was 83 months. Median overall survival (OS) was not reached; 5- and 10-year OS rates were 88.7% and 74.5%, respectively. Risk organ involvement was associated with worse PFS (hazard ratio [HR], 4.5) and OS (HR, 10.8). BRAFV600E was not associated with risk organ involvement or survival. When compared with matched unaffected US population, individuals with LCH had a significantly higher risk of overall mortality (standardized mortality ratio [SMR], 2.66), specifically among those aged <55 years at diagnosis (SMR, 5.94) and those with multisystem disease (SMR, 4.12). Second cancers occurred in 16.4% cases, including diverse hematologic and solid organ malignancies. LCH-associated deaths constituted 36.1% of deaths and occurred within 5 years of diagnosis. After 5 years, non-LCH causes of death, including second cancers, chronic obstructive pulmonary disease, and cardiovascular diseases, predominated. Our study highlights, to our knowledge, for the first time, that adults with LCH experience early and late mortality from non-LCH causes and the need for development of targeted survivorship programs to improve outcomes.

Hematopoietic stem cell transplantation (HSCT) is an effective therapy for acute leukemia (AL). Relapse represents the main cause of mortality. Isolated extramedullary relapse (iEMR) is atypical and has been related to better outcomes. Here we describe the clinical characteristics and outcomes of AL relapse after HSCT in our study population and analyze the impacts of different types of relapse on survival outcomes. This retrospective, multicenter study included 124 patients age >= 15 years with AL who underwent HSCT between 2004 and 2019. At diagnosis, 66.1% of the patients had lymphocytic AL, 19.7% presented with high-risk features, and 18.5% had extramedullary disease (EMD). At HSCT, 83.1% of the patients were in complete remission (CR), and 44.8% had negative measurable residual disease (MRD). The vast majority of donors were related (96%), including 48.4% HLA-matched and 47.6% haploidentical. Myeloablative conditioning was provided to 80.6% of patients. The median overall survival (OS) was 15 months (95% confidence interval [CI] 9.9 to 20.1 months). Factors associated with improved OS were adolescent and young adult (AYA) patient (P = .035), first or second CR (P = .026), and chronic graft-versus-host disease (GVHD) (P < .001). Acute GVHD grade III-IV (P = .009) was associated with increased mortality. The median relapse-free survival was 13 months (95% CI, 7.17 to 18.8 months); early disease status (P = .017) and chronic GVHD (P < .001) had protective roles. Sixty-eight patients (55%) relapsed after HSCT, with a median time to relapse of 6 months (95% CI, 3.6 to 8.4 months). iEMR was reported in 16 patients (23.5%). The most commonly involved extramedullary sites were the central nervous system and skin. Compared to patients with bone marrow relapse, all patients with iEMR had a diagnosis of acute lymphoid leukemia (P = .008), and 93.8% belonged to the AYA group; regarding pre-HSCT characteristics, iEMR patients had higher rates of negative MRD (P = .06) and a history of EMD (P = .009). Seventy-seven percent of relapsed patients received additional treatment with curative intent. The median OS after relapse (OSr) was 4 months (95% CI, 2.6 to 5.4 months). Factors related to increased OSr included lymphoid phenotype (P = .03), iEMR (P = .0042), late relapse (>= 6 months) (P = .014), receipt of systemic therapy including second HSCT (P < .001), and response to therapy (P < .001). Rates of relapse and iEMR were higher than those previously reported in other studies. Advanced disease, reduced-intensity conditioning, and a diminished graft-versus-leukemia effect were factors influencing these findings. At relapse, presenting with iEMR after 6 months and receiving intensive therapy with adequate response were associated with better outcomes. Our results strongly suggest that a personalized approach to treating patients with HSCT is needed to counterbalance specific adverse factors and can positively impact clinical outcomes.(C) 2023 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.

Allogeneic stem cell transplantation (alloSCT) is the only known curative treatment for myelofibrosis (MF). Risk assessment remains important for patient counseling and predicting survival outcomes for relapse and nonrelapse mortality (NRM). Outcome-prediction tools can guide decision-making. Their use in MF has relied on their extrapolation from other malignancies. The primary objective of this study was to assess the performance of the Hematopoietic cell Transplantation Comorbidity Index (HCT-CI), the augmented HCT-CI (aHCT-CI), and the Endothelial Activation and Stress Index (EASIX) in predicting NRM in patients with MF undergoing alloSCT. We retrospectively reviewed patients with MF undergoing alloSCT between 2012 and 2020 at the Mayo Clinic. Data were abstracted from the electronic medical record. EASIX score was calculated before starting conditioning therapy and analyzed based on log2- transformed values. We evaluated the log2-EASIX scores by quartiles to assess the effect of increasing values on NRM. NRM was evaluated using competing risk analyses. We used the Kaplan-Meier and log-rank methods to evaluate OS. The Fine-Gray model was used to determine risk factors for NRM. The performance of HCT-CI and aHCT-CI was compared by evaluation of model concordance given the high correlation between HCT-CI and aHCT-CI (r =.75). A total of 87 patients were evaluated. The median duration of follow-up after alloSCT was 5 years (95% confidence interval [CI], 4.4 to 6.31 years). Patients with a high HCT-CI score had significantly increased cumulative incidence of NRM at 3 years (35.5% versus 11.6%; P =.011) after alloSCT. A progressively increasing 3-year NRM was observed with increasing aHCT-CI risk category, and patients with a high or very high aHCT-CI score had significantly higher 3-year NRM compared to those with intermediate-risk or low-risk aHCT-CI scores at 3 years post-alloSCT (31.9% versus 6.52%; P =.004). An increasing log2-EASIX score quartile was not associated with 3-year NRM (19.0% versus 10.1% versus 25% versus 14.3%; P =.59), and the EASIX score was not found to be a predictor of post-transplantation NRM. A high HCT-CI was associated with significantly worse 3-year overall survival (OS) (hazard ratio [HR], 4.41; 95% CI, 1.97 to 9.87; P <.001). A high or very high aHCT-CI was significantly associated with poor 3-year OS (HR, 3.99; 95% CI, 1.56 to 10.22; P =.004). An increasing log2-EASIX score quartile group was not associated with 3-year OS (3-year OS rate, 66.7% versus 80.4% versus 64.6% versus 76.2%; P =.57). The EASIX score should not be used routinely in patients with MF. Both the HCT-CI and the aHCT-CI are accurate in predicting long-term survival outcomes in this patient population. Further studies are important to validate our findings of the role of EASIX in predicting NRM in patients with MF or other myeloproliferative neoplasms undergoing alloSCT. (C) 2023 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. (c) 2023 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Electrical properties of n-Ge contacts tailored with nanostructured WO3 is analysed using current–voltage (I-V) and capacitive-voltage (C-V) measurements. Au/WO3/n-Ge heterostructure show its significant improvement in terms of high forward current and high magnitude of rectification ratio (RR = 3040 at ± 0.5V) than compared to contact without interlayer. The series resistance evaluated using Cheung’s method found to be very low (Rs = 17 Ω) in contacts with WO3 interlayer than compared to pristine sample. The influence of WO3 interfacial layer in defining the accumulation and inversion regions is clearly observed in the C-V characteristics measured at 1 MHz. A transition from ohmic conduction at low bias voltages to trap charge limited current (TCLC) conduction at high bias voltages is observed in the case of Au/WO3/n-Ge contacts. The distribution of traps or defects at the oxide-Ge interface possibly associated to the observed current conduction mechanisms at high bias regions. Very low series resistance, high rectification ratio and high forward currents of Au/WO3/n-Ge contacts show its applicability in optoelectronic and photovoltaic applications.

Introduction Over the last decade, recurrent oncogenic alterations in the MAPK/ERK pathway have been discovered in various histiocytic and dendritic cell disorders, especially Erdheim-Chester disease (ECD), Langerhans cell histiocytosis (LCH), and Rosai-Dorfman disease (RDD). These discoveries have led to the successful use of targeted BRAF- and MEK-inhibitors. However, most data are derived from small institutional studies mostly focusing on ECD and LCH, which leaves room for a comprehensive evaluation of the molecular underpinnings in a large cohort. Methods Formalin-fixed paraffin embedded tumor biopsies from various histiocytic/dendritic cell disorders seen at a tertiary institution from 2001-2021 were subjected to whole exome sequencing (WES) using one of two assays: in-house SureSelectXT AllExon V5+UTR or commercially available Tempus xT assay. Identified variants were filtered to remove polymorphic, low coding impact and low read coverage variants. A variant was then selected for further analysis if it met one of the following criteria: 1) observed as somatic in ≥1 tumor-germline pairs or COSMIC database or 2) observed in at least three samples with an allele frequency of ≥10% in ≥1 sample. Cases were clustered into mutually exclusive groups based on their primary driver mutational profile using the following funneling order: BRAF-V600E (BRAF-V600E mutations), BRAF*/NRAS/KRAS (BRAF non-V600E, KRAS, or NRAS mutations), CSF1R (CSF1R mutations), MAPK (MAPK/MEK mutations), and PI3K (AKT3, INPP4B, MTOR, PIK3CA, PIK3R1, PIK3R2, PIK3R3, PPP2R1A, MTR mutations). A cancer specific pathway enrichment was performed on the unknown cases, which identified epigenetic mutations as major pathway alterations observed in the cohort. We also correlated the presence of epigenetic mutations with clinical features and outcomes. Results We included 114 cases with histiocytic and dendritic cell disorders in the study. Median age at diagnosis was 51y (IQR 37-64). The disease distribution was as follows: 46 LCH, 20 ECD, 17 RDD, 8 follicular dendritic cell sarcoma (FDCS), 1 adult xanthogranuloma, 12 malignant histiocytosis (MH; including histiocytic and Langerhans cell sarcoma), and 10 multicentric reticulohistiocytosis (MRH). Based on the known driver mutations in histiocytoses, the following 5 molecular groups were identified: BRAF-V600E (n= 19, 17%), BRAF*/KRAS/NRAS (n=17, 15%), MAPK (n=14, 12%), PI3K (n=8, 7%), CSF1R (n=2, 2%) (Figure 1). A large proportion (n=48, 42%) did not have any of the known driver mutations, while 6 cases (5%) had no alterations identified. Cancer-specific enrichment analysis in the entire cohort revealed mutations in epigenetic genes in 47 (41%) cases, including 30 (26%) cases with identifiable driver mutations and 17 (15%) cases without known driver mutations. Median number of epigenetic mutations was 1 (range 1-11); 21% cases had 2 and 10% cases had 3 epigenetic mutations, respectively. The most common epigenetic mutations included those in KMT2C (34%), KMT2D (23%), and ARID1A (19%). The mutational groups with highest prevalence of epigenetic mutations were CSF1R (100%), MAPK (71%), and PI3K (63%), while lowest prevalence of these alterations was found in BRAF-V600E group (16%; p=0.0003). The epigenetic gene mutations were seen more commonly in MRH (90%) and MH (50%) compared with ECD (45%), RDD (41%), FDCS (38%), and LCH (33%; p=0.037). There was no association between epigenetic gene mutations and age at diagnosis or organ involvement. The median overall survival (OS) was not significantly different between those with epigenetic mutations and those without such alterations (22y vs. 17y, p=0.89). Conclusions In this large study of patients with diverse histiocytic and dendritic cell disorders, we found a high prevalence of mutations in epigenetic genes (41%). These mutations were specifically enriched in tumors with non-BRAF-V600E mutations, and in MRH/MH. These data shed light on additional mechanisms of disease pathogenesis, and with available epigenetic therapies, warrant further investigation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Background: Rosai-Dorfman disease (RDD) is a rare histiocytic disorder with variable characteristics. The clinical presentation is varied, with patients having nodal and/or extranodal involvement. Recently, mutations in the mitogen-activated protein kinase (MAPK) pathway have been reported in a small series of RDD cases. Herein, we report the mutational profiling data by using next-generation sequencing (NGS) among 38 patients with RDD, including associations with clinical phenotype. Methods: This study was approved by the Institutional Review Board. Patients with RDD who were seen at Mayo Clinic and the University of Alabama at Birmingham (UAB) from January 2017 to December 2021 were included in this study. Data for NGS with an oncogene panel were abstracted where available. A mutation was considered pathogenic if an oncogene had a gain-of-function mutation or if a tumor suppressor gene had a loss-of-function mutation. Patients were considered to have disseminated disease if they had 2 or more extranodal organs involved. Fischer's exact test was used to compare categorical parameters and the Wilcoxon rank sum test was used to compare continuous variables. Time to systemic therapy was calculated using the Kaplan-Meier method. Systemic therapies included prednisone, cobimetinib, cladribine, or rituximab. Results: A total of 54 patients with RDD were identified. NGS was performed on 47 patients (87%). NGS for nine patients (19%) was unsuccessful because of the small biopsy size or low cellularity that yielded an insufficient quantity of DNA for testing. Among the 38 patients who had successful NGS and were included in this study, the median age at diagnosis was 56 years (range 25-79) with the majority (n=30, 79%) being females. The median follow-up duration was 3.3 years (95% CI: 1.75-4.1). 37 patients (97%) had extranodal disease with the following sites of involvement: disseminated (n=20, 53%), skin (n=9, 24%), central nervous system (n=2, 5%), bone (n=1, 3%), and other (n=5, 13%). One patient had nodal-only disease. No patients had neoplasia-associated RDD, while 2 patients had IgG4-related RDD and 1 patient had immune-related RDD. A total of 2 patients died. Two patient deaths were reported including one RDD- and one MDS-associated deaths. First-line therapies included prednisone (n=10, 26%), observation (n=10, 26%), cobimetinib (n=5, 13%), topical therapies (n=4), surgery (n=3), radiation therapy (n=3), cladribine (n=2), or rituximab (n=1). The median OS for the overall cohort was not reached (NR) [95% CI: 5.2 - NR]. Of the 38 patients who had a successful NGS, 20 out of 38 (53%) had a pathogenic mutation, which included missense KRAS mutations (n=10, 26%) and missense MAP2K1 mutations (4, 11%) [Figure]. The majority of KRAS mutations occurred at exon 3 (8/10), including p.K117N (5) and p.A146T (3). Other mutations occurred in PTEN, SMARCA4, ARAF, PIK3CA, IDH2, and NF1 genes. Among the two patients with IgG4-related disease, one had an ARAF p.S214F mutation while the other had no identifiable mutations. Among the patient with immune-related RDD, the patient had a KRAS p.A146P mutation. On univariate analysis, patients with a pathogenic mutation were more likely to have disseminated RDD compared to patients with no pathogenic mutation (80% vs. 22%, p=0.0009; odds ratio 14, 95% CI: 3-67) but age, C-reactive protein, gender, and other sites of organ involvement were not significant (Table). Patients with disseminated disease were more likely to have a pathogenic mutation compared to patients without disseminated disease (80% vs. 22%, p=0.0009). The median time to systemic therapy for patients with a pathogenic mutation was 12 months (95% CI: 2-45) versus 15 months (95% CI: 4-20) for patients without a pathogenic mutation (p=0.66). Conclusions: In our study of 38 patients, 53% of patients with RDD were found to have a known pathogenic mutation, with missense mutations in KRAS being the most frequent followed by MAP2K1. Unlike other histiocytic disorder subtypes, kinase fusions were not detected in any case. One in five patients had NGS test failure due to insufficient DNA. Patients with disseminated RDD were more likely to have a pathogenic mutation compared to those without disseminated disease but there was no difference in time to systemic therapy. Further studies are necessary to define the molecular underpinnings of non-disseminated RDD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Background Erdheim Chester disease (ECD) is a rare histiocytosis with variable clinical behavior known to be driven by recurrent activating mutations in the MAP kinase pathway. BRAF inhibitors were the first targeted therapy used in this neoplastic disorder given the presence of the BRAFV600E mutation in 50-60% of patients. Increased understanding of additional driver mutations within this pathway resulted in a study of MEK inhibitors (MEKi) in cases not harboring this mutation, ultimately leading to the FDA breakthrough designation of cobimetinib for BRAFV600E negative histiocytic neoplasms. Herein, we present data from our institution on MEKi treatment of ECD, the largest cohort to date. Methods We included all patients with ECD consecutively seen at Mayo Clinic and treated with one of the 3 available MEKi (cobimetinib, trametinib, or binimetinib) between 2019-2021. Tumor MAPK pathway mutation status was determined with next-generation sequencing (NGS) via the Tempus-xT® assay (Chicago, IL). If NGS data was unavailable, immunohistochemistry (IHC) or allele-specific PCR was used to determine BRAF-specific mutation status. Time-to-event analyses were calculated from the time of MEKi initiation to progression, therapy discontinuation due to intolerant side effects, or initiation of systemic non-MEKi therapies. Response assessment was done based on the established positron emission radiography (PET)-response criteria used for clinical trials of targeted therapies in histiocytosis. Adverse events (AEs) were graded using the National Cancer Institute Common Toxicity Criteria v5.0 Results A total of 22 patients with ECD underwent treatment with a MEKi and were included. Median follow up was 19 months (95% CI 10 - 28 months) and 55% (n=12) were female. Median age at diagnosis of ECD was 54 years (IQR 36.8 - 70.8 years). Most common system involvement included osseous (68%), retroperitoneal soft tissue (46%), central nervous system (41%), and cardiovascular (41%). Mutational assessment studies included NGS in 82% (n=18). The four remaining patients had assessment of BRAFV600E by IHC or PCR. Tumor genomic profile included non-BRAFV600E mutations in 15 patients (68%). BRAFV600E was identified by IHC in one patient. All other patients did not have successful NGS (n=2) or had no pathogenic variants identified (n=3). Additional details presented in Table 1. Median time on a MEKi was 6.5 months (IQR 3 - 15 months). It was used as first-line therapy in 72.7% (n=16) of cases. Within the 22 patients, 28 instances of MEKi initiation were observed in our cohort, as 5 patients (23%) received 2 different MEKi throughout follow up and one patient had cobimetinib rechallenge after first progression. MEKi used included: cobimetinib (n=23, 82%), trametinib (n=3, 11%), and binimetinib (n=2, 7%). Response assessment after initiation of first MEKi was not available in 1 patient. In the remaining 21 cases, overall response rate was 81% including complete or near-complete response (CR/nCR) in 5 (24%), partial response (PR) in 12 (57%), stable disease (SD) in 2 (10%), and progressive disease (PD) in 2 (10%). Median EFS was 36 months (95%CI 9 - not reached), respectively. Intolerable AEs with MEKi included G3/4 diarrhea (n=2), G3 lower extremity edema (n=2), G3 acneiform rash (n=1), G2 pericardial effusion (n=1), and "dropped-head syndrome” (n=1). Of the 6 patients who were treated with a second MEKi (Figure 1), five had data for response assessment and had CR/nCR (n=2) or a PR (n=3) as best responses. At time of last follow-up, 21 patients (96%) were alive and one died due to progression of ECD. Of the 22 patients, 10 patients (46%) remained on MEKi at the time of last follow-up. Reasons for therapy discontinuation included intolerable side effects (n=4), drug holiday after response achievement (n=4), disease progression on therapy (n=3), and change to other kinase inhibitors (n=1). Additional details regarding patient follow-up are presented in Figure 1. Conclusion Our study suggests that MEK inhibitors are a highly efficacious treatment in patients with ECD. Main limitation of our study includes its retrospective nature and sample size. While treatment discontinuation due to severe toxicities / intolerance was common, this did not preclude from maintenance of tumor response for extended periods of time. Not all patients will respond to MEKi and further research to guide individualized therapies is required. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Introduction: Hematologic abnormalities are frequent among persons living with HIV (PLWH). The bone marrow aspirate (BMA) and biopsy (BMB) are commonly performed in the diagnostic approach of patients with unexplained cytopenias. Changes in antiretrovirals, supportive therapy and increased life expectancy have modified the distribution and etiology of cytopenias, questioning their use. Our aim was to analyze the diagnostic yield of BMA, BMB and marrow cultures for the evaluation of cytopenias in PLWH. Methods: This was a retrospective cohort of >= 18-year-old PLWH undergoing bone marrow assessment (MA) for the evaluation of cytopenias between January 2002 and December 2015. Results: A total of 236 cytopenic events were analyzed, 47.9% being PLWH who had a long-standing diagnosis (>= 1 year). Adherence to antiretrovirals was 63.5%. Anemia was seen in 91.9% and pancytopenia in 39%. Common presentations included fever (52.1%), weight loss (42.8%) and adenopathies (28.8%). Median days from detection to MA was 5 (0 - 63 days). Most common etiologies were non-HIV infectious diseases (31.4%) and benign/malignant hematologic diseases (26.3%). The diagnostic yield was 16.1% for BMA, 20.3% for BMB, 30.5% for both and 35.6% when cultures were added. Patients most likely to have conclusive MA were those with moderate/severe thrombocytopenia (p = 0.007). Fever, splenomegaly, and low CD4+ counts were associated with infectious etiologies, while hematologic diagnoses were related to the presence of adenopathies. Conclusion: As a minimally invasive intervention, the MA has a high yield for identifying the etiology of cytopenic events in PLWH, being conclusive in one in three patients. Early performance could lead to prompt diagnosis and timely therapy initiation.(C) 2021 Associacao Brasileira de Hematologia, Hemoterapia e Terapia Celular. Published by Elsevier Espana, S.L.U.