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Background Complete blood count (CBC) is the most common test performed in hematology-oncology. A typical CBC report contains over 10 elements. Simplifying the report by removing nonessential elements may benefit clinicians and patients. Little is known about what elements are reported by various hospitals in the US. The objective of our study was to describe how hospitals in the US report CBC. Methods After approval from the Mayo Clinic institutional review board, we obtained hospital CBC reported elements from the Epic electronic medical records Care Everywhere health information exchange. CBCs from 2020-2023 were included. For each hospital, we determined the city and state where it's located. We obtained the number and type of elements reported in the CBC and compared the findings between academic and community hospitals. Results We collected CBC data from 139 hospitals across 43 states and 102 cities (Figure 1). Fifty-four percent were community hospitals while 46% were academic hospitals. The median number of elements reported by all hospitals was 21 (range, 12-24). This was not different (P=0.98) between academic (median 22 [range, 12-24]) and community hospitals (median 21 [range, 14-24]; Figure 2). The distribution of hospitals according to the number of CBC elements reported were as follows: 12-15 (6%), 16-19 (13%), 20 (25%), 21(6%), 22 (18%), 23 (19%), and 24 (13%). A minority of the hospitals did not report % white blood cell differential count (9.4%) or mean platelet volume (20.9%). Nucleated red blood cell and immature granulocyte count were reported frequently, 46.0% and 56.8%, respectively. However, the frequency of reporting these four elements were similar between academic and community hospitals. Conclusions We found substantial variations in CBC reporting among US hospitals even within academic and community hospitals. Most hospitals reported 20 or more elements, twice as many as the hospitals reporting the least number of elements. There is an opportunity to simplify and standardize CBC reporting, which will minimize physician burnout and distraction as well as decrease patient concern and query.

Introduction Lymphoid malignancy (LM) is a heterogenous neoplasm with respect to biology, aggressiveness, and treatment with over 100 subtypes, including Hodgkin lymphoma (HL), non-Hodgkin lymphoma (NHL), and multiple myeloma (MM). Genome-wide association studies have identified common variants associated with risk of specific LM subtypes, but less is known about the contribution of rare inherited pathogenic variants (PV) in the genetic architecture of LM risk. Rare PV have been shown to contribute to the genetic architecture of solid tumor cancer risk, many of which have been found in genes that are important to the DNA-damage repair (DDR) pathway (e.g., BRCA1, BRCA1, ATM). Here, we investigated the prevalence of PV in cancer predisposition genes regularly included on multi-gene panel testing based on NCCN guidelines and correlated with risk of LM overall and by common subtypes. Methods In this association study, cases were newly diagnosed lymphomas (excluding chronic lymphocytic leukemia) from Mayo Clinic who were enrolled between 2002 and 2015 in the Lymphoma SPORE Molecular Epidemiology Resource (MER) and MM from Mayo Clinic enrolled primarily between 1998 and 2022 in a clinical registry. Controls were from the Mayo Clinic Biobank who were enrolled between 2009 and 2016, from which we excluded individuals with a history of hematologic malignancy. All participants provided a blood sample for whole exome sequencing, performed by Regeneron on an Illumina NovaSeq panel (mean coverage of 48X). Variants were called using GATK v4 and variant annotation was performed using BioR. All loss-of-function variants (i.e., nonsense, frameshift, and consensus splice sites) and pathogenic missense in 19 cancer predisposition genes with a minor allele frequency < 0.5% were included in the analyses. Logistic regression was used to estimate odds ratio (OR) and 95% confidence intervals (CI) for the association between mutation status by gene (burden test) and risk of LM overall, and by subtype that had more than 5 mutation carriers. All analyses were adjusted for age (at diagnosis for cases and at enrollment for controls) and sex. Results A total of 6990 cases and 42432 controls were included. Median age was 63 years for both cases and controls (case range 18-94 years, control range 18-99 years). Males accounted for 58.5% (n=4090) of the cases and 41.7% (n=17762) of the controls. MM accounted for 31% (n=2138) of the cases, followed by diffuse large B-cell lymphoma (DLBCL, n=1146) and follicular lymphoma (FL, n=1132) each accounting for 16% of cases. CHEK2 (1.0%), ATM (0.4%), BRCA2 (0.4%), and BRCA1 (0.3%) had the most PV carriers in controls; these frequencies are in the range of published control populations. A total of 1816 (3.7%) individuals had a PV across the 19 genes, with 4.7% of cases and 3.5% of controls carrying any PV (OR=1.34, 95% CI: 1.18-1.51). ATM (OR=1.86, 95% CI: 1.36-2.49), CHEK2 (OR=1.74, 95% CI: 1.42-2.13) and TP53 (OR=9.07, 95% CI: 4.51-18.87) were all significantly associated with increased risk of LM overall (Figure 1). When investigating subtypes (Table 1), CHEK2 (OR=1.93, 95% CI: 1.23-2.89) and TP53(OR=10.97, 95% CI: 3.06-31.43) were significantly associated with DLBCL. ATM (OR=2.22, 95% CI: 1.13-3.90) was significantly associated with FL. ATM (OR=1.97, 95% CI: 1.16-3.12), CHEK2 (OR=1.75, 95% CI: 1.24-2.41) and TP53 (OR=7.67, 95% CI: 2.43-20.72) were significantly associated with MM and ATM (OR=8.62, 95% CI: 4.47-15.12), NBN (OR=6.94, 95% CI: 2.41-15.76) and TP53 (OR=38.30, 95% CI: 10.27-116.69) were significantly associated with mantle cell lymphoma (MCL). When subset to LM cases overall, there was no evidence of enrichment for young onset (age <60 years), male sex, or family history of hematologic malignancy between PV carriers and non-PV carriers. However, FL cases with an ATM PV tended to be less than 60 years (OR=3.21, P=0.09) compared to non- ATM PV carriers. Similarly, MM cases with a TP53 PV tended to be less than 60 years of age (OR=7.39, P=0.07) compared non-carriers. Discussion In this large case-control study, PV in established cancer predisposition genes were associated with increased risk of LM overall, demonstrating that rare inherited variants may play an important etiologic role. This study also suggests that PV in cancer predisposition genes may be subtype specific. These results will help inform LM risk for individuals who undergo genetic testing of cancer predisposition genes.

Background: Warm autoimmune hemolytic anemia (WAIHA) is mostly IgG mediated (IgG+C3-), which may at times fix complement (IgG+C3+). Whether the clinical outcome of complement-fixing (C3+) WAIHA is different from that of non-complement fixing (C3-) WAIHA remains unclear. The goal of this retrospective study was to describe and compare the clinical characteristics and treatment outcomes of patients with C3+ and C3- WAIHA. Methods: We included adult WAIHA patients seen at our institution from 2001-2023 who met all of the following criteria: A) age >18 years; B) direct antiglobulin test [DAT] IgG+ + C3+ with no cold agglutinin; and C) biochemical evidence of hemolysis. Response to treatment was based on the international consensus criteria: complete (CR; normal Hb or Hb ≥12 g/dL, with resolution of hemolysis); partial (PR; Hb >10 but <12 g/dL or Hgb >12 g/dL without resolution of hemolysis); or no response (neither CR nor PR). 223 WAIHA patients were found, and 132 patients were ultimately included. The most common reason for exclusion was a lack of complete DAT that included C3 testing. Results: There were 59 patients with C3- WAIHA and 73 patients with C3+ WAIHA, reflecting 44.7% and 55.3% of total patients respectively. Pertinent demographic, clinical, and treatment information are shown in Table 1. Slightly over half (52.3%) were males and the mean age (SD) was 63.9 years (18.1). Concomitant lymphoproliferative disease was present in 34.1% of the patients. The 3 most common treatments were steroids (97%), rituximab (66.7%), and splenectomy (18.2%). The median follow-up from diagnosis was 20.0 months (range, 1.0-251.8 months), and 14.4% of patients had died at the time of this analysis with no difference between the groups (P=0.82). There was no significant difference in the demographic composition, clinical findings, and treatment received in both groups. The number of treatments received were similar between C3- and C3+ WAIHA groups (Table 1). After first line of treatment, response was achieved in 86.4% and 94.4% of the C3- and C3+ groups (P=0.12), respectively. Additionally, 62.7% of the C3- group and 80.8% of the C3+ group were in PR or CR by their most recent CBC (P=0.02). 33.9% and 43.8% of the C3- and C3+ groups relapsed at least once (P=0.25). In those who relapsed, there was an average of 2.6 relapse events in the C3- WAIHA group compared to 1.8 relapse events in the C3+ WAIHA group (P=0.03). However, there was no difference in time to first relapse between the groups (P=0.51), shown in Figure 1. Conclusion: There have been retrospective descriptions of multiple AIHA subtypes and response rates to different therapies; however, this is one of the first studies to our knowledge to focus specifically on outcomes between complement subgroups. In our large group of patients with C3- and C3+ WAIHA, the clinical presentation, treatments utilized, and response to treatment were similar. Our data suggest that C3- and C3+ WAIHA can be approached and treated similarly.

Metastatic CUP is complex, especially NCUP. Precision oncology is crucial for rare, aggressive cancers. A 54-year-old had HER2+ neuroendocrine carcinoma of unknown origin. T-DXd treatment, response, re-challenge show importance of genomics and caution.

191 Background: ANC is used to determine the dosing of chemotherapy and eligibility in clinical trials. Duffy-null phenotype is associated with a lower ANC and present in 2/3 of the Black population. Therefore, ANC reference intervals from hospitals serving a larger percentage (%) of Black population are expected to be lower. Ideally, reference intervals should represent the normal values of the population served. The objective of this study is to determine if the ANC reference intervals of hospitals in the US are representative of the population served based on racial diversity. Methods: We obtained hospital ANC reference intervals from the Mayo Clinic EPIC electronic medical records Care Everywhere health information exchange. Reference intervals from 2020-2023 were included. For each hospital, we determined the city where it is located. For each city, the % of Black population was obtained from the 2020 US Census. We studied the correlation (Pearson) between reference ANC values and % of Black population. To determine the expected ANC reference intervals, we obtained ANC data from the 2021-2022 National Health and Nutrition Examination Survey (NHANES) and performed a reference interval simulation study. Individuals with cancer and cirrhosis were excluded. Random samples of 120 individuals were selected, consisting of n samples from Black individuals and 120-n samples from non-Black individuals. This was performed for n from 0 to 120, and repeated 1000 times per n. Results: We collected data from 107 hospitals across 40 states and 81 cities. Fifty-three (49.5%) hospitals were academic. The % of Black populations in the cities served by the hospitals was a mean of 23.4% (range, 0.7%-82.8%). There was no correlation between ANC upper (r = -0.17, p=0.07) and lower (r = 0.01, p=0.88) limits based on the % Black population. This finding was similar in both academic and non-academic hospitals. Assessment of the ANC distribution in the US population based on race by using the NHANES database showed a clear association with race at the 2.5th (p<0.001) and 97.5th (p=0.009) percentiles with an overall estimated mid-95% reference range of 2.0-8.3 for non-Black individuals and 1.3-7.7 for Black individuals. Conclusions: Hospitals serving a higher % of Black population have similar upper and lower ANC reference intervals compared to those serving a lower % of Black population. This contrasts with the findings from NHANES data which showed significant variations in the normal ANC values between Black and non-Black individuals. Therefore, current hospital ANC reference intervals may not represent the diversity of the population served. Potential clinical implications include misdiagnosis of neutropenia, delay or underdosing of chemotherapy, and inappropriate exclusion in clinical trials, especially in areas with a high % of Black population.

101 Background: In the US, minority patients are underrepresented in cancer clinical trials. This is due to multiple factors, including socioeconomic barriers, limited medical insurance coverage and restrictive clinical trial eligibility, e.g., ANC cutoff. For the latter, conservative ANC cutoff disadvantages Black patients. Two-in-three Black individuals have a Duffy-null phenotype, that is associated with lower ANC with 5% prevalence of ANC <1,500 cells/µl. To improve Black patient accrual to cancer clinical trials, lowering the ANC cutoff was proposed as a potential solution over a decade ago. Its implementation is not known. This study evaluates the ANC cutoff values as part of the eligibility criteria for cancer clinical trials. Methods: We accessed the Clinicaltrials.gov website on 5/25/2023 and obtained the ANC cutoff of cancer clinical trials conducted in the US. We included adult therapeutic trials in the phases of recruiting, not yet recruiting, enrolling by invitation, and active-not yet recruiting. Trials with drug interventions were selected. Those focusing on surgical, behavioral, nutritional and radiotherapeutic interventions were excluded. All ANC cutoff values were converted to “cells/µl” for analysis. Results: A total of 911 trials were evaluated, and 470 met the eligibility criteria. Of the 470 trials, 366 (78%) involved solid malignancies, and 104 (22%) involved hematologic malignancies. Hematologic trials have significantly lower ANC cutoffs compared to solid tumor trials with median ANC cutoff of 1,000 (range, 250-2000) vs. 1,500 (range 250-3,000); p=<0.001. In all, 323 trials (68.7%) required patients to have ANC >1,500, and 116 trials (24.6%), primarily hematologic, required patients to have ANC >1,000. For myeloma and prostate cancer, two cancers with higher incidence among Blacks, 12.9% and 86.4% of the trials require ANC >1,500, respectively. All genitourinary, breast, head & neck, sarcoma, lung, skin, and neuroendocrine tumor trials excluded patients with ANC <1,000. Conclusions: Most hematologic malignancy trials have a more liberal ANC cutoff allowing patients with ANC <1,500 to participate. However, solid tumor trials remain more conservative, with 4 in 5 trials requiring an ANC cutoff of >1,500. A strict ANC cutoff remains a barrier to minority accrual.[Table: see text]

Abstract 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 &lt;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.

Abstract 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.