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Background: Obstructive sleep apnea (OSA) imposes an afterload burden on the left ventricle and increases the pressure gradient across the intrathoracic aorta. This might increase the likelihood of aortic dissection (AD). We hypothesized that patients with acute AD would have a high prevalence of previously undiagnosed OSA and a largely nocturnal presentation. Methods: 40 consecutive, consenting subjects with acute AD who survived to hospital discharge were collected from 4 institutions. Mean age was 57 (range 28-75), 24 were male. 25 had type A dissection and 15 type B. 37 completed the modified Berlin Questionnaire and 30 had attended overnight polysomnography. Presenting CT scans had aortic diameter measured at a) the sinotubular junction b) ascending aorta c) origin of innominate d) mid-arch e) origin of left subclavian f) mid-descending aorta g) level of diaphragm; CT scans at 3 months were available in 24 subjects. Results: AHI ranged from 0 - 89; prevalence of OSA (defined by apnea-hypopnea index [AHI] > 5) was 63%. There were no differences in aortic diameter at any level comparing OSA vs non-OSA, regardless of AHI cutoff (>5, >15, >30; figure). Over time aortic diameter decreased at the level of the sinotubular junction and ascending aorta (expected - due to surgery). Whether dissection occurred during overnight hours (10 PM - 7 AM) did not differ by presence/absence of OSA (regardless of AHI cutoff). In those with high-risk Berlin questionnaires (>=2 categories positive) 10/21 (48%) dissections occurred during sleeping hours vs 2/13 (15%) in low risk Berlin group (p = 0.08, Fisher’s exact test). Conclusions: Among patients with acute AD the prevalence of OSA was high. Aortic diameters, however, were not different according to level of AHI. Presence of OSA defined by polysomnography was not associated with a nocturnal presentation in this sample.

Abstract Objective Ensuring medication delivery to the epidural space is crucial for effective transforaminal epidural steroid injections. Epidural needle placement is determined by injecting a small amount of contrast at the final needle position. The purpose of this study is to illustrate the appearance of contrast flow in the retrodural retroligamentous space of Okada during computed tomography– and fluoroscopy-guided cervical and lumbar transforaminal epidural steroid injections. Design This retrospective study will use a series of cases to demonstrate contrast within the space of Okada during epidural transforaminal steroid injections. Setting Tertiary medical center. Subjects Study subjects are adult patients who underwent transforaminal epidural steroid injection at our institution. Methods Cases were identified through the use of a search engine of existing radiology reports at our institution. Epidural steroid injection procedural reports were searched for the terms “Okada” and “retrodural space.” Images from the procedure were reviewed by the authors (all proceduralists with dedicated training in spinal injections) to confirm the presence of contrast within the space of Okada. Results This case series illustrates six examples of contrast injection into the retrodural space of Okada during cervical and lumbar transforaminal epidural steroid injections. Conclusions Contrast uptake in the retrodural space of Okada may be seen during transforaminal epidural injections. Although relatively uncommon, it is likely underrecognized. It is extremely important that providers who perform transforaminal epidural steroid injections be familiar with this non-epidural contrast flow pattern so they can adjust needle positioning to deliver steroid to the epidural space.

AbstractAlthough superior gluteal nerve (SGN) injury can have significant morbidity, to date, surgical strategies for its repair are scant in the literature. Specifically, neurotization options have not been explored. To address this deficiency in the literature, the current cadaveric feasibility study was performed. Via a transgluteal approach on 16 cadaveric sides, the proximal sciatic nerve and the entrance of the SGN into the gluteus medius and minimus were identified. Additionally, branches from the sciatic nerve to the hamstring muscles were traced proximally to confirm their position in relation to the sciatic nerve as a whole. These branches were cut at the level of the ischial tuberosity and teased away from the sciatic nerve proximally to the greater sciatic foramen and transferred superolateral to the SGN. The diameter of each nerve branch was measured as well as its available length for reaching the SGN. All branches of the sciatic nerve to the hamstring muscles arose from the anteromedial part of the nerve. The mean diameters of the branches to the semimembranosus, semitendinosus, and biceps femoris muscles were 2.1, 1.9, and 1.5 mm, respectively. The mean diameter of the SGN was 3.1 mm and the mean distance from this entrance point to the ischial spine was 7.2 cm. The mean length of the donor nerve was 8.5 cm. Based on our study, use of a tibial‐innervated hamstring branch as a donor for nerve transfer to the SGN is feasible.

Abstract Background: trALL is an important secondary primary malignancy (SPM) that has recently been appreciated. While patients (pts) with MM have an 8%-17% risk of developing an SPM while on lenalidomide (R) maintenance following autologous stem cell transplant (ASCT), trALL has been rarely observed. Little is known about the characteristics of trALL in pts with MM compared to pts who had other malignancies prior to the development of trALL. We define tALL as any prior exposure to cytotoxic chemotherapy and/or radiation for another malignancy, and herein, we report a comparative analysis of characteristics and outcomes of pts with trALL with and without MM from the Mayo Clinic Cancer Center (MCCC). Methods: We performed a systematic search in the 3-site MCCC registry and included all pts diagnosed and received at least 1 cycle of ALL-directed therapy and/or underwent allogeneic transplantation (AlloHCT) for ALL between 2007-2020. All cases of trALL in this series are B-ALL. Comparisons of characteristics between trALL patients with and without MM were made using a Wilcoxon rank sum test (continuous variables) or Fisher's exact test (categorical variables). Time-to-event variables were compared using unadjusted Cox proportional hazards regression models. Results: 70 trALL pts (14 MM [20%], 56 non-MM [80%]) were identified during the study period. The median age at trALL diagnosis was 63.9 (range 47-71) for MM pts and 63.1 (range 18.2-84) for non-MM pts. Median follow-up from trALL diagnosis was 1.42 years (range 0.02-10.6 years). The most common prior non-MM malignancies among tALL pts were breast (28.6%), lymphoma (17.9%), myeloid (17.9%), and GU/GYN (14.3%). Amongst the 14 MM pts, 100% (n=10) had ISS-I disease, 8 (57%) had IgG K MM, 1 (n=10) had high risk cytogenetics, 8 (57.1%) received R-based induction , 4 (28.6%) received CyBorD induction, 4(28.6%) received VRD induction, 3 (21.4%) received RD induction. 10 (71.4%) pts were actively on R when they developed trALL, 8 (57.1%) pts received prior ASCT. The median time to develop trALL following ASCT for MM was 46.3 months (m), (95% CI 20.4-67.6), 12 (85.7%) pts received R maintenance with a median duration of 53m (95% CI 16.9-121). The median time to develop trALL after initiation of R maintenance was 61.2m (95% CI 16.9-123.4). The most common trALL induction regimen received was HyperCVAD which was used in 71.4% of MM pts and 51.8% of non-MM pts. In comparison to non-MM pts, MM patients had a significantly lower WBC at diagnosis (Median: 2.0 vs. 5.8, P=0.005),no t(9;22) BCR/ABL1 cytogenetics (0.0% vs. 35.7%, P=0.008), a higher frequency of hypodiploid/near-triploid (Ho-Tri) cytogenetics (42.9% vs. 12.5%, P=0.009), and a lower frequency of prior radiation therapy (7.1% vs. 44.6%, P=0.012). MM pts had a higher frequency of AlloHCT for trALL (71.4% vs. 42.9%, P=0.075) and were more commonly in complete response (CR) at transplant (100.0% vs. 70.8%, P=0.078). No trALL in MM pts were Ph-like ALL. There was a statistically significant difference in time to development of trALL between previous malignancy locations (P=0.018), with GU/GYN (Median: 9 years) having the longest time and myeloid (Median: 3 years) having the shortest time; MM was 6 years. In the overall pt cohort, 56 (80%) pts achieved a complete response after induction and 60% (n=25) were minimal residual disease (MRD)+ after induction. Pts with MM had a significantly lower likelihood of being MRD+ after induction (OR=0.09, P=0.015). Overall, 24.3% of pts relapsed after induction therapy for trALL; 39 (55.5%) died after trALL diagnosis including 43% (n=35) who died after AlloHCT. Although pts with MM tended to have better outcomes compared to non-MM trALL pts in terms of overall survival after trALL diagnosis (Figure 1A), survival after AlloHCT (Figure 1B), relapse rate after trALL diagnosis and non-relapse mortality after AlloHCT, none of these findings were statistically significant in this small cohort (Figure 1C). Conclusion: trALL is a unique SPM that can occur in pts with MM. It is associated with Ho-Tri cytogenetics and is BCR/ABL1 negative. The majority of MM pts that developed trALL had undergone prior ASCT and were on R maintenance when they developed trALL. Despite being more likely to have adverse cytogenetics features, MM-associated trALL has similar survival compared to non-MM-associated trALL which speaks to the poor survival outcomes of this SPM. Further research on trALL in MM pts is merited. Figure 1 Figure 1. Disclosures Litzow: Amgen: Research Funding; Pluristem: Research Funding; AbbVie: Research Funding; Actinium: Research Funding; Astellas: Research Funding; Omeros: Other: Advisory Board; Jazz: Other: Advisory Board; Biosight: Other: Data monitoring committee. Bergsagel: Janssen: Consultancy. Fonseca: Scientific Advisory Board: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Caris Life Sciences: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy; Patent: Prognosticaton of myeloma via FISH: Patents & Royalties; Bayer: Consultancy; Takeda: Consultancy; Celgene: Consultancy; Amgen: Consultancy; BMS: Consultancy; Mayo Clinic in Arizona: Current Employment; Juno: Consultancy; Kite: Consultancy; Aduro: Consultancy; OncoTracker: Consultancy, Membership on an entity's Board of Directors or advisory committees; GSK: Consultancy; Novartis: Consultancy; Merck: Consultancy; Sanofi: Consultancy; Pharmacyclics: Consultancy; Janssen: Consultancy. Dispenzieri: Takeda: Research Funding; Alnylam: Research Funding; Pfizer: Research Funding; Oncopeptides: Consultancy; Sorrento Therapeutics: Consultancy; Janssen: Consultancy, Research Funding. Murthy: CRISPR Therapeutics: Research Funding. Ailawadhi: GSK: Consultancy, Research Funding; Sanofi: Consultancy; Pharmacyclics: Consultancy, Research Funding; Takeda: Consultancy; Medimmune: Research Funding; Xencor: Research Funding; Genentech: Consultancy; Janssen: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Cellectar: Research Funding; Beigene: Consultancy; BMS: Consultancy, Research Funding; AbbVie: Consultancy; Karyopharm: Consultancy; Ascentage: Research Funding. Foran: actinium: Research Funding; taiho: Honoraria; bms: Honoraria; servier: Honoraria; pfizer: Honoraria; novartis: Honoraria; OncLive: Honoraria; abbvie: Research Funding; boehringer ingelheim: Research Funding; takeda: Research Funding; trillium: Research Funding; aptose: Research Funding; revolution medicine: Honoraria; syros: Honoraria; sanofi aventis: Honoraria; certara: Honoraria; gamida: Honoraria; kura: Research Funding; h3bioscience: Research Funding; aprea: Research Funding; sellas: Research Funding; stemline: Research Funding.

Abstract Background: Outcomes of patients with relapsed/refractory AML (RR-AML) have remained poor. Therapy with venetoclax based combinations in this setting leads to CR/CRi rates of 21-49% (DiNardo CD et al. Am J Hematol 2018, Aldoss I et al. Haematologica 2018, Stahl M et al. Blood Adv 2020). Preclinical studies with BCL-2 inhibitors indicate potential mechanisms of drug resistance including overexpression of the anti-apoptotic protein MCL-1 (Konopleva et al. Cancer Cell. 2006). Pevonedistat is a first in class inhibitor of Nedd8 activating enzyme that induces the pro-apoptotic protein NOXA leading to neutralization of MCL-1 and apoptosis. Preclinical studies evaluating the combination of pevonedistat and venetoclax against AML cell lines have demonstrated a synergistic effect (Knorr KL et al. Cell Death Differ. 2015). Hence, we designed a phase I study to assess the safety and tolerability of adding pevonedistat to the combination of azacitidine and venetoclax in patients with RR-AML. Study design and methods: We conducted a phase I study with the combination of pevonedistat, venetoclax and azacitidine in patients with RR-AML. Patients aged 18 years or above with morphologically documented RR-AML, ECOG performance status 0-2 and adequate organ function were eligible. Major exclusion criteria were isolated extramedullary relapse, hematopoietic cell transplantation (HCT) within 100 days of enrollment, and active acute GVHD. Previous therapy with hypomethylating agents (HMA) or venetoclax was not an exclusion criterion. The dose escalation phase was conducted using 3+3 design. Treatment included azacitidine (75 mg/m 2 daily x 7 days), venetoclax (400 mg daily x 28 days), and pevonedistat in escalating doses (10-20 mg/m 2 IV days 1,3,5 of each cycle) with a cycle length of 28 days. Pevonedistat was given at 10 mg/m 2 dose in cohort 1, 15 mg/m 2 dose in cohort 2 and 20 mg/m 2 dose in cohort 3. The primary endpoint is to determine the recommended phase 2 dose (RP2D) and toxicity profile of pevonedistat, azacitidine and venetoclax. Other endpoints included determination of response rates, duration of response, survival, pharmacokinetics, correlation of response rates with AML genomic profile, correlation of pretreatment levels of BCL2, BCLXL, MCL1, BAX or BAK with response, determination of changes in NOXA (PMAIP1) mRNA and protein expression pre-and post-pevonedistat treatment, evaluation of BH3 mimetic profiling on bone marrow samples by flow cytometry and assessing the sensitivity of leukemia and leukemic stem/progenitor cells to pevonedistat ex vivo. Results: Thirteen patients participated in the dose escalation phase, 12 of whom were evaluable. Median age was 69 years (61-91), 30.8% had secondary/therapy related AML, 69.2% with adverse risk disease, 53.8% previously received venetoclax/HMA and 23.1% had relapse after prior allogeneic hematopoietic cell transplantation (HCT) (Table 1). Seven patients were enrolled into cohort 1 (pevonedistat 10 mg/m 2 dose) of which one was not evaluable, three patients enrolled into cohort 2 (pevonedistat 15 mg/m 2 dose), and three patients enrolled into cohort 3 (pevonedistat 20 mg/m 2 dose). Grade 3 or higher AEs included febrile neutropenia (23%), infection (15%), anemia (38%), neutropenia (54%), thrombocytopenia (38%). There was 1 dose limiting toxicity (DLT) in cohort 1 (atrial fibrillation) that triggered cohort expansion. However, subsequent patients did not experience DLT despite planned dose escalation. Of the 12 evaluable total patients, CR/CRi was observed in 5 (41.6%) patients. Notably, patients with RR-AML who were venetoclax/HMA naïve had a CR/CRi 83.3% (5/6 patients). The response rates for each cohort are summarized in Table 2. Three of the five patients with CR/CRi (60%) achieved MRD negativity by flow cytometry. Four patients who achieved CR/CRi proceeded to allogeneic HCT after therapy. Median OS of the cohort was 5.4 months (1.8-14) and median OS was not reached in patients with CR/CRi. Conclusions: The addition of pevonedistat to venetoclax and azacitidine backbone is safe and well tolerated in patients with RR-AML. Dose escalation yielded encouraging efficacy in venetoclax/HMA naïve RR-AML patients. The study is currently in the dose expansion phase. Details on correlative studies examining mechanisms of therapeutic efficacy and resistance will be reported in the main meeting. Figure 1 Figure 1. Disclosures Guru Murthy: Cardinal health: Honoraria; TG Therapeutics: Other: Advisory board meeting; DAVA Oncology: Honoraria; CancerExpertNow: Honoraria; Qessential: Honoraria; Techspert: Consultancy; Curio Sciences: Honoraria; Guidepoint: Consultancy. Abedin: AltruBio: Research Funding; Helsinn: Research Funding; Amgen: Honoraria; Pfizer: Research Funding; Agios: Honoraria; Actinium: Research Funding; Astellas Pharma Inc.: Research Funding. Litzow: Jazz: Other: Advisory Board; Pluristem: Research Funding; Actinium: Research Funding; Amgen: Research Funding; Astellas: Research Funding; AbbVie: Research Funding; Omeros: Other: Advisory Board; Biosight: Other: Data monitoring committee. Atallah: Novartis: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Research Funding; BMS: Honoraria, Speakers Bureau; Takeda: Consultancy, Research Funding; Abbvie: Consultancy, Speakers Bureau; Amgen: Consultancy.

Abstract Introduction: The gut microbiome is a potentially modifiable factor in treatment related outcomes in allogeneic hematopoietic cell transplant (HCT). Prior studies have linked pre- or mid-treatment gut microbiome diversity with risk for treatment related morbidity and mortality. However, these studies have been limited by the inclusion of one or only a few institutions and the lack of longitudinal sampling with high quality metadata. These limitations complicate the interpretation of microbiome alterations over the course of HCT. Methods: To overcome these, we devised and implemented a large-scale biospecimen collection protocol in conjunction with BMT CTN 1703, a randomized, multicenter, Phase III trial of tacrolimus/methotrexate vs. post-transplant cyclophosphamide/tacrolimus/mycophenolate mofetil in reduced intensity conditioning (RIC) allogeneic HCT (NCT03959241). Patients enrolled on 1703 were optionally co-enrolled in the companion immune and microbiome profiling study, 1801 (MI-IMMUNE). This involved blood, urine and stool sampling before conditioning (PCON), then weekly starting on day 0 through day 77 (through day 84 for blood), and on days 98, 180, 270, 365 and 730. For all enrolled participants where the donor consented, residual donor cells were saved from the empty hematopoietic stem cell product bag for later analysis. Additionally, the protocol included one-time blood, urine and stool sample collection from consented matched related donors (MRDs) prior to stem cell collection. Starting with protocol version 4.0 on February 1, 2021, participation in 1801 stool collection was required for the first six out of eighteen sample collection timepoints. Participation in later stool and urine timepoint collections remained optional. Here we review the feasibility of creating a multi-institutional biobank. Additionally, we assess the success of our strategies by calculating sample collection compliance and standard deviation in compliance across centers for each timepoint. Results: On June 18, 2021, BMT CTN 1703/1801 closed to accrual with 431 patients enrolled on 1703; 323 patients from 36 centers were co-enrolled on 1801. 304 (94%) provided study samples, making this the largest prospective microbiome and immune profiling study in HCT patients to date. As of July 6, 2021, 3,683 blood, 2,668 urine, and 2,098 stool samples had been collected. Across the first 6 timepoints for all participating centers, blood, urine and stool sample collection averaged 93%, 82%, and 74% compliance, respectively. Of the 99 (30%) patients enrolled on 1801 with a MRD, 34 (34%) donors consented to sample collection. Sample collection compliance was lower for MRDs than for patients on the study with 76%, 74%, and 62% of expected blood, urine and stool samples collected, respectively, from this group. For stool collection exclusively, a median of 5 samples were collected per patient across the first 6 timepoints (median of 6 across all timepoints) with 93 (31%) of patients completing a full sample set through Day 28. 139 (46%) patients provided at least one sample after day 28; these represented 37% of the total samples collected to date. The PCON sample, which provides an important measure of pre-treatment gut microbiome diversity, had the third highest compliance with 74% of patients providing a sample. Surprisingly, Day 28 had the lowest compliance (66%) and highest standard deviation (37%) possibly because this timepoint often falls around the time of hospital discharge. Between PCON and day 28, the standard deviation between sites in the average collection compliance (24%) and number of samples collected per patient (1.1) was small indicating the successful adoption of stool collection across institutions. Table 1 summarizes sample collection statistics. Conclusion: Overall this study has resulted in a large, novel biobank of blood, urine and stool samples from patients undergoing RIC allogeneic HCT at 36 centers across the US. This will serve as a valuable resource for investigating the role of the gut microbiome in long term health outcomes following HCT. Although the results of 1801 are forthcoming given ongoing sample collection, the size and composition of the biobank to date clearly demonstrate the feasibility of implementing multi-institutional stool collection. This study represents a critical step towards the large-scale adoption of microbiome sampling as a diagnostic tool. Figure 1 Figure 1. Disclosures Chhabra: GSK: Honoraria. Clark: Kadmon: Consultancy. Horowitz: Mesoblast: Research Funding; Shire: Research Funding; Vertex: Research Funding; Stemcyte: Research Funding; Vor Biopharma: Research Funding; Janssen: Research Funding; Miltenyi Biotech: Research Funding; Kiadis: Research Funding; Sobi: Research Funding; Kite/Gilead: Research Funding; Pfizer, Inc: Research Funding; Jazz Pharmaceuticals: Research Funding; Magenta: Consultancy, Research Funding; Medac: Research Funding; Novartis: Research Funding; GlaxoSmithKline: Research Funding; Daiicho Sankyo: Research Funding; Xenikos: Research Funding; Omeros: Research Funding; Orca Biosystems: Research Funding; Pharmacyclics: Research Funding; Regeneron: Research Funding; Tscan: Research Funding; Takeda: Research Funding; CSL Behring: Research Funding; Genentech: Research Funding; Gamida Cell: Research Funding; Chimerix: Research Funding; Bristol-Myers Squibb: Research Funding; bluebird bio: Research Funding; Astellas: Research Funding; Amgen: Research Funding; Allovir: Consultancy; Actinium: Research Funding; Sanofi: Research Funding; Seattle Genetics: Research Funding. Jenq: Microbiome DX: Consultancy; Merck: Consultancy; Prolacta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kaleido: Consultancy, Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Research Funding; Seres: Consultancy, Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; LisCure: Consultancy, Membership on an entity's Board of Directors or advisory committees; MaaT Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karius: Consultancy. Levine: Equillium Bio: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Research Funding; Kamada: Research Funding; Biogen: Research Funding; Omeros: Membership on an entity's Board of Directors or advisory committees; Symbio: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Talaris Therapeutics: Membership on an entity's Board of Directors or advisory committees; Viracor: Patents & Royalties: GVHD biomarker patent with royalties from Viracor; Mesoblast: Consultancy, Research Funding; X4 Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Murthy: CRISPR Therapeutics: Research Funding. Riches: ATARA Biotherapeutics: Other: Payment; BioIntelect: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Other: Payment. Sung: Merck: Research Funding; Novartis: Research Funding; Enterome: Research Funding; Seres: Research Funding; AVROBIO: Consultancy; Abbott Nutrition: Honoraria; Clasado: Other: Research Product; DSM: Other: Research Product. Al Malki: Neximmune: Consultancy; Jazz Pharmaceuticals, Inc.: Consultancy; Rigel Pharma: Consultancy; Hansa Biopharma: Consultancy; CareDx: Consultancy. Rezvani: Kaleido: Other: One-time scientific advisory board; Nohla Therapeutics: Other: One-time scientific advisory board; Pharmacyclics-Abbvie: Research Funding; US Department of Justice: Consultancy. Bolaños-Meade: Incyte Corp: Consultancy. Holtan: Incyte: Consultancy, Research Funding; Generon: Consultancy. Saber: Govt. COI: Other. Hamadani: Sanofi, Genzyme, AstraZeneca, BeiGene: Speakers Bureau; Janssen, Incyte, ADC Therapeutics, Omeros, Morphosys, Kite: Consultancy; Takeda, Spectrum Pharmaceuticals and Astellas Pharma: Research Funding. Kean: Bluebird Bio: Research Funding; Bristol Myers Squibb: Patents & Royalties: From clinical trial data, Research Funding; Vertex: Consultancy; Novartis: Consultancy; Gilead: Research Funding; Regeneron: Research Funding; EMD Serono: Consultancy. Perales: Cidara: Honoraria; Servier: Honoraria; Incyte: Honoraria, Other; Equilium: Honoraria; Takeda: Honoraria; Novartis: Honoraria, Other; Nektar Therapeutics: Honoraria, Other; NexImmune: Honoraria; MorphoSys: Honoraria; Omeros: Honoraria; Karyopharm: Honoraria; Sellas Life Sciences: Honoraria; Merck: Honoraria; Miltenyi Biotec: Honoraria, Other; Medigene: Honoraria; Bristol-Myers Squibb: Honoraria; Kite/Gilead: Honoraria, Other; Celgene: Honoraria.

Abstract Background: Palliative care (PC) benefits patients with cancer and those undergoing hematopoietic stem cell transplantation (HSCT), but remains under-utilized in HSCT. While transplant physicians have substantial concerns regarding how patients perceive PC, studies examining HSCT recipients' perceptions of PC are lacking. Methods: Between 11/2020-4/2021, the CIBMTR Survey Research Group conducted a multi-site cross-sectional survey of adult autologous and allogeneic HSCT recipients at 11 transplant centers in the United States who were 3-12 months post-transplant to assess their experience, knowledge, and perceptions of PC. Using validated questionnaires, we assessed patients' familiarity with PC, knowledge and perception of PC, unmet PC needs, quality of life, and symptom burden. We computed a composite score of patients' perceptions of PC (mean = 48.8, SD = 12.2). We used a generalized linear regression model to examine factors associated with patients' perceptions of PC. Results: Of 359 potentially eligible patients, 250 (69.6%) enrolled in the study and 249 were eligible for analysis. Median participant age was 58.1 years (IQR 16.6). Most were white (85.9%), non-Hispanic or Latino (95.2%), and male (53.0%). Overall, 63.1% underwent autologous HSCT. The most common diagnoses were multiple myeloma (42.2%), lymphoma (22.1%), leukemia (16.9%), and MDS/MPN (12.4%). Overall, 44.2% (110/249) of patients reported limited knowledge about PC and 51.0% (127/249) endorsed being familiar with PC. Most patients stated that when they hear the term PC, they feel hopeful (54%), and reassured (50%) while a minority reported feeling scared (21%), stressed (22%), or depressed (15%) [Figure 1]. Most endorsed that when a PC referral is suggested for them, they think their doctor really cares about what is happening to them (83%), and only 7% of patients stated that when a PC referral is suggested, they think their doctor has given up on them [Figure 2]. In multivariate analyses, patients who were more knowledgeable about PC were more likely to have a positive perception of PC (B = 7.54, SE=1.61, P < 0.001) compared to those who had less knowledge about PC. Patients with postgraduate education were more likely to have a negative perception of PC (B = -5.55, SE=2.60, P = 0.034) compared to those with high school education or less. Patients' demographics, HSCT type, diagnosis, unmet PC needs, quality of life, and symptom burden were not statistically significantly associated with their perceptions of PC. Conclusions: A substantial proportion of HSCT recipients report limited knowledge and familiarity with PC. Most patients reported positive perceptions of PC, and those who were more knowledgeable about PC were more likely to have positive perceptions of PC. These data do not support transplant physicians' concerns about how patients perceive PC and underscore the need for future interventions to further educate patients about PC to overcome barriers to PC utilization in HSCT. Figure 1 Figure 1. Disclosures Burns: Astellas Pharma Inc.: Research Funding; Medac GmbH: Research Funding; Sanofi: Research Funding; OncoImmune: Research Funding; Fate: Research Funding; Bristol Meyers Squibb: Research Funding; PrioThera: Research Funding; Kyowa Kirin International: Research Funding. Murthy: CRISPR Therapeutics: Research Funding. LeBlanc: Amgen: Consultancy, Other: travel; Pfizer: Consultancy, Other: Advisory Board; AstraZeneca: Consultancy, Honoraria, Other: Advisory board, Research Funding; Flatiron: Consultancy, Other: Advisory board; Agios: Consultancy, Honoraria, Other: Advisory board; Travel fees, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Other: Travel fees, Research Funding, Speakers Bureau; Daiichi-Sankyo: Consultancy, Honoraria, Other: Advisory board; AbbVie: Consultancy, Honoraria, Other: Advisory board; Travel fees, Speakers Bureau; Helsinn: Consultancy, Research Funding; Duke University: Research Funding; Jazz Pharmaceuticals: Research Funding; UpToDate: Patents & Royalties; NINR/NIH: Research Funding; CareVive: Consultancy, Other, Research Funding; Otsuka: Consultancy, Honoraria, Other; American Cancer Society: Research Funding; Seattle Genetics: Consultancy, Other: Advisory board, Research Funding; Astellas: Consultancy, Honoraria, Other: Advisory board; Heron: Consultancy, Honoraria, Other: advisory board.