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Background: Osteochondritis dissecans (OCD) occurs most commonly in the knees of young individuals. This condition is known to cause pain and discomfort in the knee and can lead to disability and early knee osteoarthritis. The cause is not well understood, and treatment plans are not well delineated. The Research in Osteochondritis Dissecans of the Knee (ROCK) group established a multicenter, prospective cohort to better understand this disease. Purpose: To provide a baseline report of the ROCK multicenter prospective cohort and present a descriptive analysis of baseline data for patient characteristics, lesion characteristics, and clinical findings of the first 1000 cases enrolled into the prospective cohort. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients were recruited from centers throughout the United States. Baseline data were obtained for patient characteristics, sports participation, patient-reported measures of functional capabilities and limitations, physical examination, diagnostic imaging results, and initial treatment plan. Descriptive statistics were completed for all outcomes of interest. Results: As of November 2020, a total of 27 orthopaedic surgeons from 17 institutions had enrolled 1004 knees with OCD, representing 903 patients (68.9% males; median age, 13.1 years; range, 6.3-25.4 years), into the prospective cohort. Lesions were located on the medial femoral condyle (66.2%), lateral femoral condyle (18.1%), trochlea (9.5%), patella (6.0%), and tibial plateau (0.2%). Most cases involved multisport athletes (68.1%), with the most common primary sport being basketball for males (27.3% of cases) and soccer for females (27.6% of cases). The median Pediatric International Knee Documentation Committee (Pedi-IKCD) score was 59.9 (IQR, 45.6-73.9), and the median Pediatric Functional Activity Brief Scale (Pedi-FABS) score was 21.0 (IQR, 5.0-28.0). Initial treatments were surgical intervention (55.4%) and activity restriction (44.0%). When surgery was performed, surgeons deemed the lesion to be stable at intraoperative assessment in 48.1% of cases. Conclusion: The multicenter ROCK group has been able to enroll the largest knee OCD cohort to date. This information is being used to further understand the pathology of OCD, including its cause, associated comorbidities, and initial presentation and symptoms. The cohort having been established is now being followed longitudinally to better define and elucidate the best treatment algorithms based on these presenting signs and symptoms.

Abstract With the development of various strategies of anti-CD19 immunotherapy for treatment of B cell malignancies, it remains to be elucidated whether CD19 targeting with a monoclonal antibody impairs subsequent CD19 targeted chimeric antigen receptor T cell (CART19) therapy. In this study, we evaluated the potential interference between the CD19 targeting monoclonal antibody tafasitamab and CART19 treatment (using a construct similar to the FDA approved therapy, FMC63-41BBζ, tisagenlecleucel) in preclinical lymphoma and leukemia models. For in vitro assays, the CD19 + cell lines JeKo-1 (mantle cell lymphoma), Nalm6 (acute lymphoblastic leukemia), and OCI-Ly7 (diffuse large B cell lymphoma) were used. When CART19 were co-cultured with CD19 + tumor cells in the presence of increasing concentrations of tafasitamab (10-400 µg/mL) or the isotype control, an impairment of CART19 functions at the highest concentration of tafasitamab was observed. However, when tafasitamab was cocultured with tumor cells overnight and removed from the culture by washing, there was no impairment of CART19 anti-tumor activity or effector functions compared to a pre-culture with isotype control. We then aimed to validate these findings in xenograft mouse models by determining whether prior tafasitamab treatment impairs subsequent CART cell function. First, a two-step JeKo-1 xenograft model was created through inoculation of 1x10 6 luciferase + JeKo-1 cells to immunocompromised NOD-SCID-γ -/- (NSG) mice via tail vein injection. One week later, tumor burden was assessed by bioluminescence imaging (BLI) and mice were randomized to receive either 1) PBS (Group 1) or 2) 10 mg/kg of tafasitamab (Group 2) (Fig. 1A). Treatment was performed until the mice reached the endpoint due to the high tumor load. When reaching the endpoint, mice were euthanized and spleen was harvested. Splenic cells were then injected to naïve NSG mice. Two weeks after the inoculation of splenic cells (PBS or tafasitamab treated), mice were imaged with BLI and randomized according to their tumor burden to receive 2x10 6 of 1) untransduced T cells (UTD) or 2) CART19 (i.v.) (Fig. 1B). Mice, treated with CART19 demonstrated potent anti-tumor effects and showed prolonged survival compared to UTD control mice. Interestingly, CART19-treated mice inoculated with Group 2 splenic cells (pretreated with tafasitamab) showed a significantly better tumor control and overall survival compared with mice engrafted Group 1 splenic cells (PBS pretreatment) (Fig. 1C). This finding led us to further investigate the effects of prior tafasitamab therapy on subsequent CART19 treatment. In this context, we studied the sequential treatment with tafasitamab and CART19 in an additional JeKo-1 xenograft model (Fig. 1D). In brief, NSG mice were inoculated with luciferase + JeKo-1 on day -14. On day -8, mice were imaged and randomized to the PBS (Group I) or tafasitamab (10 mg/kg) group. On day -1 tafasitamab treated mice were imaged again, randomized to the tafasitamab discontinuation (Group II) or continuation (Group III). Treatment with PBS was continued in Group I. All groups were administered with 1x10 6 of CART19 on day 0. Cotreatment of JeKo-1 xenografts with tafasitamab and CART19 led to impaired anti-tumor activity presumably as a result of CD19 binding competition between tafasitamab and CART19 (Group III). Mice treated with tafasitamab followed by CART19 had improved tumor control compared to mice treated with PBS followed by CART19 (Fig. 1E-F). Serial peripheral blood analysis demonstrated that mice from Group I showed the highest CART19 expansion on day 10. Strikingly, Group II exhibited weak CART19 expansion at day 10, but strongest expansion on day 23 (Fig. 1G). We therefore hypothesized that prior treatment with tafasitamab results in modulation of CART19 cell activation. To test this hypothesis, spleens of satellite mice were harvested 24 hours after CART19 administration. Flow cytometric analysis revealed that the mice from Group II showed significantly lower CD69 and HLA-DR expression on CART19 cells compared with Group I, and reduced apoptosis as measured by the Annexin assay (Fig. 1H-I). In summary, concomitant treatment of tafasitamab and CART19 led to impaired anti-tumor activity while, in contrast, sequential treatment of tafasitamab and CART19 did not inhibit CART19 anti-tumor activity but rather promoted anti-tumor effects in xenograft models. Figure 1 Figure 1. Disclosures Sakemura: Humanigen: Patents & Royalties. Augsberger: MorphoSys AG: Current Employment. Schanzer: MorphoSys AG: Current Employment. Patra-Kneuer: MorphoSys AG: Current Employment. Heitmüller: MorphoSys AG: Current Employment. Steidl: MorphoSys AG: Current Employment. Endell: MorphoSys AG: Current Employment. Ding: DTRM: Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees. Parikh: Pharmacyclics, MorphoSys, Janssen, AstraZeneca, TG Therapeutics, Bristol Myers Squibb, Merck, AbbVie, and Ascentage Pharma: Research Funding; Pharmacyclics, AstraZeneca, Genentech, Gilead, GlaxoSmithKline, Verastem Oncology, and AbbVie: Membership on an entity's Board of Directors or advisory committees. Kay: Acerta Pharma: Research Funding; Targeted Oncology: Membership on an entity's Board of Directors or advisory committees; Oncotracker: Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; Behring: Membership on an entity's Board of Directors or advisory committees; CytomX Therapeutics: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rigel: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Sunesis: Research Funding. Nowakowski: Celgene, NanoString Technologies, MorphoSys: Research Funding; Celgene, MorphoSys, Genentech, Selvita, Debiopharm Group, Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cox: Humanigen: Patents & Royalties. Kenderian: Humanigen, Inc.: Consultancy, Honoraria, Research Funding.

Abstract Introduction: Plasmablastic lymphoma (PBL) is an aggressive B-cell lymphoma that predominantly occurs in patients with HIV or other causes of immunodeficiency. Frequent infection by the Epstein-Barr virus (EBV) and MYC translocations have been described as major features contributing to the pathogenesis of PBL. Prior studies examining the genetic landscape of PBL have largely relied on targeted capture-based sequencing approaches. As such, the molecular features of PBL remain to be fully explored. Here, we provide a comprehensive description of the genomic landscape of PBL using whole-genome and whole-exome sequencing to identify commonly perturbed pathways. Method: Archival diagnostic fresh frozen and formalin fixed paraffin embedded tissue biopsies from 58 PBL tumours were accrued from Lymphoma/Leukemia Molecular Profiling Project (LLMPP) sites, including 15 tumours from Ramis-Zaldivar et al., Haematolgica 2021. MYC rearrangements were identified by break-apart fluorescent in situ hybridization (FISH) and rearrangement partner was determined in a subset of tumours from capture or genome sequencing data using structural variant callers Manta, GRIDSS, and Delly. High confidence somatic mutations (SNVs/Indels) were identified in data from whole-genome (n=5) or whole-exome (n=53) sequencing through an ensemble voting approach utilizing four variant callers (Strelka2, Lofreq, Mutect2, SAGE). Mutation frequencies in known lymphoma-related genes were compared to activated B-cell (ABC)-DLBCL (Schmitz et al., NEJM 2018), as the closest tumour entity in terms of putative cell-of-origin differentiation stage, to identify differences in genetic aberrations. Candidate somatic copy number alterations (CNAs) were identified from exome and genome sequencing data, using CopywriteR and ControlFREEC, respectively, and high-confidence CNAs were determined using GISTIC2.0. Results: Within the study cohort, 81% of patients were male with a median age of 59 years (range 11-88). HIV and EBV statuses were available for 47% of patients and 95% of tumours, respectively, with 49% (13/27) of the patients being HIV+ and 69% (38/55) of tumours being EBV+. MYC rearrangement was observed in 60% (35/58) of PBLs, with IGH as the partner gene in 88% (21/24) of tumours. The most frequently mutated genes were STAT3 (38%), TP53 (22%), NRAS (21%), and TET2 (16%), consistent with previous studies, however novel mutations were seen in DUSP2 (21%), KLHL6 (16%), and BHLHE41 (16%). Recurrent CNAs included amplifications in 1q, whole gains of 7, 8q24, 11p12 and deletions affecting 4p16, 5p15, 10q11.22. While the mutational landscapes were similar between samples with and without a MYC translocation, the MYC-translocated PBLs showed more frequent amplification of 1q32.1. When stratifying by EBV status, STAT3 and SOCS1 mutations were more frequent in EBV-positive tumours, whereas TP53, TET2, KRAS, and MMRN2 mutations were associated with EBV-negativity. In comparison to ABC-DLBCL, PBLs were significantly enriched in STAT3 and NRAS mutations, and lacked common mutations affecting the NF-κB pathway (eg. MYD88, CD79B, and NFKBIZ 3' UTR mutations). Mutations in genes that are frequently mutated in ABC-DLBCLs, such as those associated with plasma cell differentiation (eg. PRDM1) or a memory B-cell fate (eg. TBL1XR1), were also not mutated in PBLs. Finally, genetic alterations associated with immune evasion, such as deletion of MHC I and II and mutations in B2M, CIITA, and CD58, were rarely observed. Conclusion: These data present a comprehensive overview of the genomic landscape of PBLs in a large cohort. We show frequent mutations involving the JAK-STAT and MAPK pathways, wherein the genetic landscape can be differentially characterized by EBV status and MYC rearrangement status. We show that PBLs are genetically distinct from ABC-DLBCLs, with absence of mutations in genes affecting the NF-κB pathway, immune evasion, and driving a memory B-cell fate. Disclosures Slack: Seagen: Consultancy, Honoraria. Raess: Scopio Labs: Research Funding. Holte: Gilead: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Nordic: Membership on an entity's Board of Directors or advisory committees; Nanovector: Membership on an entity's Board of Directors or advisory committees, Other: lectures honorarias; Novartis: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Savage: Servier: Consultancy, Honoraria; Roche: Research Funding; BMS: Consultancy, Honoraria, Other: Institutional clinical trial funding; Astra-Zeneca: Consultancy, Honoraria; Merck: Consultancy, Honoraria, Other: Institutional clinical trial funding; AbbVie: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Takeda: Other: Institutional clinical trial funding; Beigene: Other: Institutional clinical trial funding; Genentech: Research Funding. Steidl: Seattle Genetics: Consultancy; Curis Inc.: Consultancy; Bayer: Consultancy; Epizyme: Research Funding; Trillium Therapeutics: Research Funding; AbbVie: Consultancy; Bristol-Myers Squibb: Research Funding. Rimsza: NanoString Technologies: Other: Fee-for-service contract. Morin: Foundation for Burkitt Lymphoma Research: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Epizyme: Patents & Royalties. Scott: Abbvie: Consultancy; AstraZeneca: Consultancy; Rich/Genentech: Research Funding; BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. ; Incyte: Consultancy; Janssen: Consultancy, Research Funding; Celgene: Consultancy; NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling..

Abstract Introduction: Daratumumab is approved across lines of therapy for multiple myeloma (MM) by subcutaneous administration (DARA SC) or by intravenous administration (DARA IV). In clinical studies, the administration time ranges from 3-5 minutes for DARA SC versus 3-7 hours for DARA IV, and DARA SC is associated with reduced rates of administration-related reactions (ARRs). These characteristics of DARA SC are associated with benefits for clinics in terms of safety and clinic time. We previously reported DARA administration characteristics at Mayo Clinic infusion centers: DARA SC had shorter total clinic and total chair times compared with DARA IV, and DARA SC was associated with very low rates of ARR-related events (Soefje S, et al. EHA Library. 2021). Based upon this analysis, the treatment plan was modified to reduce the mandated observation time for DARA SC to improve clinic efficiency. Here, we describe updated clinical administration characteristics for DARA SC at Mayo Clinic infusion centers before and after the reduction in procedure-mandated observation time, versus DARA IV, using a novel empirical data extraction approach from Electronic Health Records (EHR). Methods: Patients ≥18 years of age with an ICD-9/10 diagnosis code of MM and a first DARA treatment between April 5, 2017 and June 22, 2021 were identified in Mayo Clinic's EHR database. Data were extracted using a scheduling and pharmacy software that tracked patient movement through appointments at a Mayo Clinic infusion center. On May 3, 2021, the Mayo treatment plan was amended to shorten the mandated post-administration observation time for DARA SC from 4 to 2 hours for Dose 1 and from 1 hour to 30 minutes for Doses 2 and 3, with no mandated observation time for Doses 4+. In this analysis, data were captured for patients initiating DARA IV throughout the defined treatment window. For DARA SC, data were captured for patients starting DARA SC therapy on the initial treatment plan (before May 3, 2021; DARA SC initial) and after the change to shorten the mandated post-administration observation time for DARA SC (after May 3, 2021; DARA SC shortened). Time-based measures included: total clinic time (check-in time through patient check-out); total chair time (time from infusion room entry to infusion room exit or check-out time, including order review, pharmacy preparation time, and post-administration observation time); and observation time (time from the end of medication administration to infusion room exit or patient check-out). The medication administration time documented for DARA SC was 0 minutes due to the default duration for SC injections in the EHR. Results: In total, 755 (DARA IV, n=586; DARA SC initial, n=145; DARA SC shortened, n=24) patients received DARA treatment for MM. For all doses combined, the median total clinic time was 2.9 hours shorter for DARA SC compared with DARA IV (DARA IV, 4.9 hrs; DARA SC initial, 2.0 hrs). The median total clinic time for DARA SC and DARA IV was highest at Dose 1 (DARA IV, 9.5 hrs; DARA SC initial, 6.1 hrs; DARA SC shortened, 4.4 hrs) and lower for subsequent doses (Dose 4+: DARA IV, 4.6 hrs; DARA SC initial, 1.7 hrs; DARA SC shortened, 1.6 hrs; Figure). Similarly, the median total chair time was 2.7 hours shorter in the DARA SC group compared with the DARA IV group for all doses combined (DARA IV, 4.1 hrs; DARA SC initial, 1.4 hrs). The median total chair time for DARA SC and DARA IV was highest at Dose 1 (DARA IV, 8.8 hrs; DARA SC initial, 5.6 hrs; DARA SC shortened, 3.9) and lower for subsequent doses (Dose 4+: DARA IV, 3.7 hrs; DARA SC initial, 1.1 hrs; DARA SC shortened, 1.1 hrs). Conclusion: Marked reductions in the amount of time spent both in clinic and in chair were observed with DARA SC compared with DARA IV, with additional time savings observed following the Mayo procedure change to reduce the DARA SC mandated observation time. These favorable DARA SC administration characteristics may indicate a reduction in the burden on both clinical resources and patients in Mayo Clinic infusion centers. These results add to the growing body of evidence supporting the use of DARA SC as an efficient and convenient treatment administration option for patients with MM. Figure 1 Figure 1. Disclosures Soefje: Beigene: Consultancy; Pfizer: Speakers Bureau; Janssen: Consultancy, Research Funding. Carpenter: nference Inc.: Current Employment; Janssen: Consultancy. Carlson: nference Inc.: Current Employment; Janssen: Consultancy. Awasthi: nference Inc.: Current Employment, Current holder of individual stocks in a privately-held company; Janssen: Consultancy. Lin: Janssen: Current Employment. Kaila: Janssen Scientific Affairs, LLC: Current Employment. Kayal: nference Inc.: Current Employment; Janssen: Consultancy. Kirkup: nference Inc.: Current holder of individual stocks in a privately-held company, Ended employment in the past 24 months; Path AI: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Wagner: nference Inc.: Current Employment; Janssen: Consultancy. Gray: Janssen Scientific Affairs, LLC: Current Employment, Current holder of individual stocks in a privately-held company. Kumar: Oncopeptides: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Carsgen: Research Funding; Antengene: Consultancy, Honoraria; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Bluebird Bio: Consultancy; Beigene: Consultancy; Tenebio: Research Funding; Roche-Genentech: Consultancy, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding.

Abstract Background: Generalizability of results from clinical trials with narrow in-/exclusion criteria are a concern as significant deviations in efficacy or toxicity may occur when treatments are used in populations of elderly and more comorbid patients. The cost-effectiveness of novel therapies may also be less favorable if real-world treatment effects are inferior to clinical trial results. In diffuse large B-cell lymphoma (DLBCL), a recent US study showed that baseline organ function-based eligibility criteria had substantial impact on survival with ineligible patients being at higher risk of dying from progressive lymphoma (1). Aims: The present study explored the impact of commonly used in-/exclusion criteria in key completed and ongoing first line DLBCL trials on survival in a Danish population-based study of patients with de novo DLBCL. Patients and methods: DLBCL patients enrolled in the Danish Lymphoma Registry (LYFO) and treated with R-CHOP in the period 2008-19 were screened for completeness of data to match trial eligibility criteria. The key organ/hematology eligibility criteria of completed or ongoing all-comers DLBCL studies (REMoDL-B, Goya, Polarix and Hovon84) were collected (bilirubin, ALAT, creatinine, eGFR, leucocytes, neutrophils, thrombocytes and ECOG). First, high-level trial matching on disease risk group (Ann Arbor, bulky disease, international prognostic index (IPI)) and age-groups were performed so that patients assessed for trial eligibility had a relevant risk profile. Subsequently, patients were divided into eligible or ineligible based on selected in/exclusion criteria. For each trial, overall survival (OS) from treatment start were compared for eligible and ineligible patients using inverse probability of treatment weighted Kaplan-Meier and log-rank tests. Crude OS and OS adjusted for residual imbalances in IPI and age were estimated. When possible, the OS curves from standard arms of the original trials were superimposed on OS plots. For each trial, the Shapley value of each criterion was calculated, using the HRs as well as the 5y restricted loss of lifetimes (RLOLs). The Shapley value measures the average influence of each eligibility criterion on the estimated IPI- and age-adjusted HR/5y RLOL. Results: A total of 3,150 R-CHOP treated DLBCL patients without discordant low-grade lymphoma were identified in the surveyed period. A total of 1,666 patients (52.89% of surveyed population) were available for the REMoDL-B trial, 1,431 (45.43%) for Goya, 1,125 (35.71%) for Polarix, and 1,432 (45.46%) for Hovon84. The variations of numbers for each trial evaluation were explained by trial inclusion criteria and missing data in LYFO. Crude OS estimates for patients with and without all necessary information were similar (data not shown). OS curves for eligible and ineligible patients are shown in Figure 1 and, when possible, with superimposed trial results (Goya, REMoDL-B, Hovon84). Survival differences between trial eligible and ineligible patients were robust to further adjustment of imbalances in age and IPI. Associated crude and adjusted 2 and 5-year OS rates for trial eligible and ineligible are shown in Table 1. The largest numerical difference in 2-year crude OS between eligible and ineligible was observed in the REMoDL-B trial (ineligible had 26% lower 2-year OS rate). The largest numerical difference in 2-year OS adjusted for IPI and age between eligible and ineligible was observed for the Polarix trial (ineligible had 17% lower 2-year OS rate). The strongest drivers of OS differences between trial eligible and ineligible patients in terms of the tested eligibility criteria were thrombocyte count (HR-contribution calculated from Shapley values -0.11; -0.14) and ECOG (HR-contribution -0.09; -0.21). Liver function parameters (bilirubin and ALAT) had low impact on OS (HR-contribution 0.00; -0.05 and 0.00; 0.07). Conclusions: The present population-based study confirms that trial ineligible patients have worse survival even after adjustments in imbalances in age and disease risk category. Thus, trial eligibility criteria have substantial impact on generalizability of results to a wider unselected population. Interestingly, the trial eligible patients identified in the present study had very similar outcomes to R-CHOP treated patients in the original trials supporting the possible use of RWD as synthetic control arms. Figure 1 Figure 1. Disclosures Maurer: Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Nanostring: Research Funding; Genentech: Research Funding; Celgene: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Jørgensen: Novartis: Consultancy; Gilead: Consultancy; Roche: Consultancy; Celgene: Consultancy. Larsen: BMS: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Odense University Hospital, Denmark: Current Employment; Gilead: Consultancy. Clausen: Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expences ASH 2019; Gilead: Consultancy, Other: Travel expences 15th ICML ; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Poulsen: Abbvie: Consultancy; Janssen: Consultancy. El-Galaly: Abbvie: Other: Speakers fee; ROCHE Ltd: Ended employment in the past 24 months.

Abstract Objectives: We identified a case of follicular lymphoma (FL) that transformed into a morphologic diffuse large B-cell lymphoma (DLBCL), which by gene expression profiling showed a primary mediastinal (PMBL)-like gene expression profile (GEP) (Lymph3Cx; Blood 2018;132:2401-5). A search identified 4 additional transformed FL (tFL) cases with a PMBL-like GEP, which we further studied to determine how similar these tFLs were to classic cases of PMBL. Methods: The morphology and previously reported immunophenotype were reviewed, and CD30, CD23, MAL, CD273/PDL2, and CD200 immunohistochemical stains (IHC) were performed. Whole exome sequencing (WES) and copy number analysis (CNA) to evaluate genes typically altered in FL and PMBL were performed. Results: None of the tFLs arose in the mediastinum or had a previous history of mediastinal disease. All cases showed typical centroblastic DLBCL cytology, with fine sclerosis typical of PMBL. 3/3 were GCB by the Hans IHC algorithm, 1/3 were MYC+, 3/3 BCL2+, 1/5 CD30+, 3/5 CD23+, 4/5 MAL+, 0/5 CD273/PDL2+, 1/5 CD200+, and 0/2 EBER+. Rearrangements of MYC, BCL2, or BCL6 were identified by FISH in 0/3, 1/3, and 2/3 cases, respectively. WES demonstrated sequence variants in genes associated with both FL (CREBBP [60%], KMT2D [40%], and TNFRSF14 [40%]) and PMBL (JAK-STAT pathway genes [80%], B2M [20%], and CD58 [20%]). 2 of the mutations identified in the tFLs have previously been shown to result in JAK-STAT activation (STAT6 p.E372K [PNAS 2016;113:13015-20] and SOCS1 p.F101L [Oncogene 2002;21:4351-62] identified in 1/5 cases each). CNA showed gains/amplification of REL in 3/5 cases, gains/amplification of STAT6 in 2/5, gains of large sections of chromosome 16, including IL4R, in 2/5, and both deletions and gains of 11q in 1/5. See Figure demonstrating the 5 cases on the Y-axis and the chromosomes on the X-axis. Conclusions: The tFLs in this small series seem to represent PMBL-like DLBCLs, rather than classic PMBLs, and have a blended pattern of immunophenotypic and genomic features between FL/DLBCL and PMBL. Although the cases express some PMBL-associated markers (CD23 and MAL), there is less frequent staining for others (CD30, CD273/PDL2, and CD200). The cases harbor both FL-associated and PMBL-associated sequence variants, including 40% with mutations known to activate the JAK-STAT pathway. This frequency of mutations in JAK-STAT pathway genes is higher than that seen in typical FL/DLBCL, but perhaps lower than in classic PMBL (Blood 2019;134:802-13). PMBL also frequently has gains/amplifications of 9p24.1, which was not seen in our cohort. However, gains/amplification of REL/2p, which is seen in approximately 50% of PMBL, was identified in 60% of the tFLs. The 11q aberration identified in 1 case would be unusual for PMBL, and is instead more commonly associated with a subset of aggressive lymphomas with Burkitt-like features (Haematologica 2019;104:1822-9). Recently, lymphomas with similar blended features between DLBCL and PMBL, which were not arising in the setting of tFL, have been reported (Duns G, et al. Blood 2021). Our study extends the types of biological transformations, in addition to more classic DLBCL, that can be seen in FL. These tFLs with blended PMBL-DLBCL biology may have implications for therapeutic decision making including targeted therapies used in PMBL. Figure 1 Figure 1. Disclosures Rimsza: NanoString Technologies: Other: Fee-for-service contract. Steidl: Curis Inc.: Consultancy; Trillium Therapeutics: Research Funding; Bayer: Consultancy; Epizyme: Research Funding; Seattle Genetics: Consultancy; AbbVie: Consultancy; Bristol-Myers Squibb: Research Funding.

AbstractAn infant was referred for evaluation of congenital glaucoma and corneal clouding. In addition, he had a pelvic kidney, hypotonia, patent ductus arteriosus, abnormal pinnae, and developmental delay. Exome sequencing identified a previously unpublished de novo single nucleotide insertion in PBX1 c.400dupG (NM_002585.3), predicted to cause a frameshift resulting in a truncated protein with loss of function (p.Ala134Glyfs*65). Identification of this loss of function variant supports the diagnosis of congenital anomalies of the kidney and urinary tract syndrome with or without hearing loss, abnormal ears, or developmental delay (CAKUTHED). Here, we propose glaucoma as an extra‐renal manifestation associated with PBX1‐related disease due to the relationship of PBX1 with MEIS1, MEIS2, and FOXC1 transcription factors associated with eye development.

Abstract BACKGROUND Validation of the 2016 LANO MRI scorecard for leptomeningeal metastasis failed for multiple reasons. The objective of this joint EORTC Brain Tumor Group and RANO effort was to validate the feasibility of the revised MRI scorecard for assessing response in leptomeningeal metastasis. METHODS Coded paired cerebrospinal MRI of 20 patients with leptomeningeal metastases from solid cancers at baseline and follow-up after treatment and instructions for assessment were provided via the EORTC imaging platform. The kappa coefficient (K) was used to evaluate inter-observer pairwise agreement. Statistical analyses were performed using SAS V9.4 software (Cary, NC). The sponsor of the study was the University Hospital Zurich (2018-00192). RESULTS Thirty-five raters participated, including 9 neuroradiologists, 17 neurologists, 4 radiation oncologists, 3 neurosurgeons and 2 medical oncologists. Among leptomeningeal metastases-related items at baseline, the best median concordance was noted for hydrocephalus (K=0.63), and the worst median for spinal linear enhancing disease (K=0.46). The median concordance for overall response was moderate (K=0.44). Notably, the interobserver agreement for the presence of parenchymal brain metastases at baseline was minimal (K=0.29). Significant differences were observed when considering the specialty of the raters. Only 394 of 700 ratings (56%) were fully completed. Among 394 fully completed ratings, perfect concordance was noted in 293 ratings (74%) when comparing the overall response according to the guidelines provided in the scorecard and the overall response provided by the raters. The main discordances were noted for partial response according to the rater versus stable disease according to the guidelines (n=44), followed by progression according to the raters versus stable disease according to the guidelines (n=23). CONCLUSION Electronic case report forms with "blocking solutions" are probably required to enforce completeness and quality of scoring. These results confirm the necessity of central review and the need for training of MRI assessment in clinical trials.