Davidge‐Pitts, Caroline

AbstractErdheim–Chester disease (ECD) is a histiocytic neoplasm that predominantly harbors mitogen‐activated protein kinase (MAPK) pathway variants. MAPK inhibitors typically are effective treatments, but mutations outside the MAPK pathway, such as CSF1R variants, may cause refractory ECD. We describe a patient with a novel somatic mutation in CSF1R (CSF1RR549_E554delinsQ) that resulted in refractory ECD affecting the central nervous system. Cell model studies, RNA sequencing analysis, and in silico protein modeling suggested that she had a gain‐of‐function mutation occurring in a region critical for autoinhibition. The patient was treated with pexidartinib, a CSF1R inhibitor, and has had a complete clinical and metabolic response lasting more than 1.5 years to date. To our knowledge, this is the first report to describe successful treatment of a patient with ECD by using an agent that specifically targets CSF1R. This case also highlights the critical role of individualized molecular profiling to identify novel therapeutic targets in ECD.

Abstract Introduction Histiocytic disorders pose significant diagnostic and management challenges for the clinicians due to diverse clinical manifestations and often non-specific histopathologic findings. Herein, we report the tumor board experience from the first-of-its-kind Histiocytosis Working Group (HWG). Materials and Methods The HWG was established in June 2017 and consists of experts from 10 subspecialties that discuss cases in a multidisciplinary format. We present the outcome of tumor board case discussions during the first 2 years since its inception (June 2017-June 2019). Results Forty cases with a suspected histiocytic disorder were reviewed at HWG during this time period. Average number of subspecialties involved in HWG case discussion was 5 (range, 2-9). Histiocytosis Working Group tumor board recommendations led to significant changes in the care of 24 (60%) patients. These included change in diagnosis (n = 11, 27%) and change in treatment (n = 13, 33%). Conclusion Our report highlights the feasibility of a multidisciplinary tumor board and its impact on outcomes of patients with histiocytic disorders.

Abstract INTRODUCTION Rosai-Dorfman disease (RDD) is a rare histiocytic disorder associated with histiocytes expressing high level of macrophage colony stimulating factor receptor (c-fms). Mutations in mitogen-activated protein kinase (MAPK) pathway have been reported in RDD, indicating an underlying clonal process in some patients. Aberrant activation of MAPK pathway can occur due to mutations or high c-fms expression. Data on the use of MAPK/extracellular-signal-related kinase (ERK)-inhibitor therapy in RDD are very limited. Cobimetinib is a MEK inhibitor, which is listed in the National Comprehensive Cancer Network Compendium ® for the treatment of RDD. We present our retrospective experience of cobimetinib treatment in a large series of patients with RDD. METHODS Following approval of the institutional reviewed board, patients (pts) with RDD who were consecutively seen at Mayo Clinic and treated with cobimetinib between 2013-2021 were included. Response was assessed as described by Goyal et al (Haematologica 2020;105:2). Cobimetinib was given 20-60 mg once a day by mouth for 21 days in a 28-day cycle. Adverse events (AEs) were graded using the National Cancer Institute Common Toxicity Criteria v5.0. Time-to-event analyses were calculated from the time of treatment initiation, while duration of response was calculated from the time of 1 st response. Tumor genomic profile was analyzed using Tempus-xT ® assay (Chicago, IL), which includes targeted DNA sequencing (648 oncogenes) and whole transcriptome sequencing. RESULTS Of the 54 pts with RDD, ten were treated with cobimetinib and included in this study. The median follow-up was 16 months (m) [95% confidence interval (CI): 13-not reached (NR)] and most (n=8; 80%) were females. The median age at the time of treatment was 63 years (range: 36-74). Cobimetinib was used as first line therapy in four pts. Overall response rate was 70%, with 30% and 40% achieving complete (CR) and partial (PR) responses, respectively. One had stable disease (SD) and two had progressive disease (PD) (Table 1). The median progression-free-survival was 6.4 m (95%CI: 4.9-NR) and at 6 and 12 m, 67% and 50% of pts remained free from disease progression or death, respectively (Figure 1). The median duration of response was 7.6 m (95%CI: 3.1-NR). At the time of last follow-up, nine (90%) pts were alive. One pt died due to myelodysplastic syndrome with excessive blasts. She had multiple chemotherapy treatments before initiation of cobimetinib. Cobimetinib was discontinued in this pt due to grade 3 anemia and skin toxicity after 6 m of therapy and had SD as the best response. Median duration of treatment for the entire cohort was 6 m (range: 2-14). In the seven pts who responded, the median duration of treatment was 7 m (range: 2-14). Cobimetinib was discontinued in seven pts: disease progression (n=3; one disease progression after achieving PR and two PD while on therapy), grade 3 left ventricular systolic dysfunction (n=1), grade 3 diarrhea (n=1), grade 3 anemia (n=1), and grade 2 creatinine elevation (n=1). Five (50%) pts were started at a reduced dose of cobimetinib at the discretion of treating physician [20 mg (n=4) and 40mg, (n=1)]. Two pts were started at 60 mg and dose reduced to 20 mg after one cycle of treatment due to grade 2 skin toxicity in one and grade 2 skin toxicity and diarrhea in the other. Both pts achieved a PR but progressed after four and six cycles, respectively. One pt started at 40 mg and reduced to 20 mg due to grade 2 skin toxicity after two cycles achieving a PR. The response was sustained in this pt for at least 9 months, until the time of last follow-up (Table 1). Tissue molecular testing showed five pts with MAPK pathway alterations and all of them responded to therapy (CR=3 and PR=2). Of the other five pts who either did not have a MAPK pathway alteration (n=4) or had test failure (n=1), responses were observed in two (40%) pts, both PR (Table 1). CONCLUSION Our study suggests that cobimetinib is an effective treatment in RDD, with responses observed in all pts having MAPK pathway alterations. Less than half of pts without a MAPK pathway alteration achieved a response. However, treatment discontinuations due to AEs were common despite dose reductions. Patients who were treated at low doses of cobimetinib also had remarkable clinical response. Further studies are needed in evaluating other MAPK pathway inhibitors with better toxicity profile to improve adherence and outcomes. Figure 1 Figure 1. Disclosures Tobin: National Institutes of Health: Research Funding; Mayo Clinic Center for MS and Autoimmune Neurology: Research Funding; Mallinckrodt Pharmaceuticals: Research Funding. Bennani: Vividion: Other: Advisory Board; Kyowa Kirin: Other: Advisory Board; Daichii Sankyo Inc: Other: Advisory Board; Verastem: Other: Advisory Board; Purdue Pharma: Other: Advisory Board; Kymera: Other: Advisory Board. Vassallo: Pfizer: Research Funding; Bristol-Myers-Squibb: Research Funding; Sun Pharma.: Research Funding.

SummaryErdheim–Chester disease (ECD) is a rare histiocytic neoplasm with frequent multiorgan involvement. An accurate diagnosis of ECD requires the correlation of clinical features, histopathologic and radiologic findings. We describe a case series of patients with a referral diagnosis of ECD, whereby the diagnosis was changed to non‐histiocytic diseases after comprehensive review at a tertiary care center. This accurate revision of the referral diagnosis of ECD enabled initiation of proper disease‐directed therapy in a timely manner for these patients and avoided unnecessary exposure to systemic cytotoxic chemotherapy or targeted agents. Our study highlights the value of a multidisciplinary team of histiocytosis experts in confirming the diagnosis of ECD and also brings attention to other conditions to consider that can mimic ECD, including osteopoikilosis, tenosynovial giant cell tumour, IgG4‐related disease, fibrous dysplasia and chronic recurrent multifocal osteomyelitis.

7050 Background: Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm manifesting as unifocal, multifocal, multisystem (MS) or pulmonary LCH (smoking-related). In pediatric LCH, somatic BRAFV600E prevalence is reported at 55-70%, and associated with increased risk of multisystem disease and early treatment failure. Our aim was to describe the prevalence of BRAFV600E mutation and evaluate its association with clinical manifestations and outcomes in adults with LCH. Methods: A retrospective review of adult patients diagnosed with LCH consecutively seen at Mayo Clinic from 2011 to 2020 was performed.Evaluation of association of BRAFV600E mutational status and clinical factors was conducted by the Chi-square test for independence. Progression-free survival (PFS) and overall survival (OS) were analyzed via the Kaplan Meier method and compared with the log-rank test to assess the effect of BRAFV600E. Results: Of the total LCH cohort ( n= 128), 88 patients with available BRAFV600E results were included in the study. Median age at diagnosis was 41y (range 19 - 88); 52.3% were male. 40 (45.5%) patients had a BRAFV600E mutation. Increasing age was associated with BRAFV600E (10-year increase OR 1.42, 95%CI 1.07-1.89; p= 0.017). No correlation was observed between BRAFV600E status and site of disease, risk organ (RO: liver, spleen, marrow) involvement, or MS disease. Patients with BRAFV600E were 4 times more likely to receive targeted therapy ( BRAF inhibitor) than non- BRAFV600E patients ( p= 0.018). After a median follow up of 46 mo (95% CI 30.8-61.2), PFS was similar between BRAFV600E and non- BRAFV600E patients ( p= 0.167). However, patients with BRAFV600E had a worse 3-year OS compared with non- BRAFV600E patients (84% vs. 97.1%, p= 0.027). Patients who died had a significantly higher age at LCH diagnosis (median 62 vs. 38 years; p= 0.0002). Conclusions: In our cohort of adults with LCH, BRAFV600E was less frequent than reported in pediatric literature and was associated with worse OS. The frequency of BRAFV600E was positively correlated with increasing age. Contrary to reports in pediatric LCH, there were no significant associations between BRAFV600E and high-risk or multisystem disease.[Table: see text]

7049 Background: Langerhans cell histiocytosis (LCH) can manifest as single system (SS) disease, multisystem (MS) disease, or pulmonary LCH (smoking-related). There is a paucity of data on prognostic factors including risk organ (RO) involvement (liver, spleen, and bone marrow) in adult LCH, which we sought to address in this study. Methods: Single-center retrospective study of patients ≥18y diagnosed with LCH from 1998 to 2020. Univariate and multivariate analyses for progression free survival (PFS) and overall survival (OS) were conducted using age, sex, organ involvement, LCH subtype, year of diagnosis, BRAF V600E status, and treatments. Results: We included 219 patients with LCH; median age 43y (range 19-88), females 51%, SS unifocal (23%), SS multifocal (6%), pulmonary (31%) and MS (40%). Commonly involved organs included lung (53%), bone (42%), skin (24%), pituitary (16%), and CNS (12%). BRAF V600E was positive in 40/88 (46%). Median follow-up duration was 6.1y (95% CI, 5.1- 7.1). On univariate analysis, factors associated with worse PFS were bone LCH, RO involvement, multifocal/MS LCH, and radiation therapy alone; those with worse OS included RO involvement, MS disease, BRAF V600E+, and age ≥45y at diagnosis. In multivariate analysis, BRAF V600E and age ≥45y at diagnosis were associated with worse mortality (Table). Median PFS was not reached (NR-NR) for SS unifocal LCH, 5mo (0-12.7) for SS multifocal LCH, 110mo (84.7-135.3) for pulmonary LCH, and 27mo (17.2-36.8) for MS LCH. 5-year OS was 97.4% for SS unifocal LCH, 100% for SS multifocal LCH, 96.1% for pulmonary LCH, and 79.9% for MS LCH. 41 (18.7%) developed a second primary malignancy (SPM), of which 11 were hematologic neoplasms. There was a trend towards a higher prevalence of SPMs in patients with BRAF V600E (28% vs. 17%; p = 0.22). Conclusions: In our large single-center study, PFS for multifocal and MS LCH was worse than SS unifocal or pulmonary LCH. RO involvement was not associated with outcomes in multivariate analysis. Overall prognosis was excellent for all subtypes except MS LCH. BRAF V600E and older age were associated with worse OS. The prevalence of SPMs was very high and needs to be explored further.[Table: see text]

Abstract Background: Accurate interpretation of laboratory values with sex-specific reference ranges presents a challenge in transgender individuals on gender affirming hormone therapy (GAHT). Creatinine (Cr), the most common marker used for kidney function, varies significantly with body mass and composition. Both Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-Epi) equations account for sex in estimating glomerular filtration rate. GAHT can effect Cr values in 2 potential ways: 1) by causing changes in muscle mass and body fat redistribution as early as 3 months after GAHT initiation and 2) by direct effects of sex hormones on kidney function. Previous studies have shown Cr values approaching affirmed gender identity as early as 6 months when on GAHT without mention of sex steroid levels. In this study we sought to describe the changes in serum Cr after initiation of GAHT in an effort to better understand expected changes and interpretation of lab data in TG individuals. Methods: A retrospective chart analysis on all adult TG patients initiated on GAHT at our institution from January 2011 to 2020 was completed. We reviewed demographics, baseline health information, body mass index, and lab values including Cr, sex hormone levels, A1C, and fasting blood glucose. Lab values were obtained prior to GAHT, at the start of GAHT, at 3, 6, and 12 months after GAHT. Matched pair testing was conducted with sex steroid levels and Cr values in transgender men (TM) on testosterone and transgender women (TW) on estradiol in order to compare the median pre GAHT Cr to median Cr levels at 3, 6, and 12 months. Results: 84 TW with a median age of 30 and 24 TM with a median age of 23 were included for analysis. TW and TM had a low rate of existing kidney disease (4.9%, 0%), diabetes mellitus (4.8%, 0%), and hypertension (10.8%, 4.5%) respectively. TW on GAHT achieved a goal estradiol level (≥100 pg/ml) at a rate of 37.3%, 51.7%, and 71.1% and suppressed testosterone to a goal level (<60ng/ml) at a rate of 44.4%, 54.7%, and 76.5% at 3, 6, and 12 months respectively. There was no significant change in Cr values at 3 months, but significantly decreased on average by -0.07 (p<0.001) at 6 months, and by -0.09 (p<0.001) at 12 months. TM on GAHT achieved a goal testosterone level (≥240 ng/dl) at a rate of 64.3%, 80.0%, and 72.3% at 3, 6, and 12 months respectively. Cr values increased significantly on average by 0.14 (p=0.036) at 3 months, by 0.21 (p=0.004) at 6 months, and by 0.15 (p=0.003) at 12 months. Conclusions: In TW on GAHT, clinicians can consider using affirmed gender Cr reference ranges as early as 6 months. Similarly in TM on GAHT, affirmed gender Cr reference ranges can be used as early at 3 months. It remains to be seen whether changes in Cr levels reflect changes in sex steroid levels or sex steroid direct effects. Additionally, research is needed to determine if change in Cr levels reflect true changes in GFR.

Abstract Objective: Transgender and gender-diverse individuals are at risk of insufficient treatment of endocrine diseases due to a number of barriers to care. There are currently no data evaluating the prevalence of thyroid disease in this population, and it is unknown if gender-affirming hormone therapy affects treatment of thyroid disease in these individuals. Methods: Utilizing a registry of 676 patients over 18 years of age who were seen in our Transgender and Intersex Specialty Care Clinic from 2015-2019, we identified 554 individuals seeking medical therapy for gender dysphoria/incongruence. Of these, 56 patients were taking thyroid hormone or antithyroid medications or had a coded diagnosis of thyroid disease; 2 were excluded as they were receiving thyroid hormone as adjunctive therapy for refractory depression. 54 patients were therefore analyzed with respect to thyroid disease (TD+), and compared to those 498 patients without thyroid disease (TD-) with regard to average vital signs, demographics, and presence of common comorbidities. Results: Fifty percent of our TD+ patients were recorded female sex at birth, and 98% were Caucasian. TD+ patients were much more likely to have essential hypertension (OR 5.99), to use tobacco (OR 2.23), and to be overweight or obese (OR 2.16) than TD- patients. Due to the evolving natural history of disease, some TD+ patients belonged to multiple categories: 48 patients, 26 trans feminine and 21 trans masculine, had hypothyroidism, of whom 41 had overt hypothyroidism and 2 patients had subacute thyroiditis that progressed to the hypothyroid phase of illness. 5 patients (3 trans masculine and 2 trans feminine) demonstrated hyperthyroidism, 4 of whom had Graves’ Disease. 2 patients had multinodular goiter, both trans masculine. 2 patients had thyroid malignancies, both trans feminine, of whom one had proven follicular thyroid carcinoma and the other had unspecified thyroid malignancy. Among hypothyroid patients, there was a slight non-significant trend toward increased thyroid hormone requirements while receiving treatment with estradiol or testosterone. Conclusion: To our knowledge, this represents the first attempt to characterize the prevalence of various thyroid disease states in the gender diverse population. Our data corresponded to a prevalence of hypothyroidism of approximately 8.7%, which is higher than previously published estimates of 3-5% in the general population. Whether this represents actual increased prevalence or assessment bias is uncertain. It is important for all health professionals who care for gender diverse people to identify and appropriately treat thyroid disease, and to monitor thyroid function closely if gender-affirming hormone therapy is initiated.

AbstractNonsuppressed levels of testosterone are seen in up to a quarter of transgender women on gender-affirming feminizing hormonal treatment. Multiple factors contribute to this situation, including patient, medication, laboratory, and organ-specific concerns. We propose a stepwise approach to determine the etiology of nonsuppressed levels of testosterone in transgender women. This may lead to an appropriate feminizing hormonal therapy regimen and diagnosis of manageable medical conditions.