Clinical characteristics, molecular aberrations, treatments, and outcomes of malignant histiocytosis

Malignant histiocytosis (MH) is an extremely rare neoplasm of the macrophage-dendritic cell lineage. We report the clinical characteristics, molecular aberrations, treatments, and outcomes of patients with MH seen at two referral centers from January 2000 to May 2023. We identified 43 patients with MH, of which 26 had histiocytic sarcoma (MH-H), 9 interdigitating dendritic cell sarcoma (MH-IDC), and 8 Langerhans cell sarcoma (MH-LC). The median age at diagnosis was 61 years (range, 3-83). Thirty-three patients (77%) had multifocal disease, while 10 had unifocal involvement. Tumor specimens from 22 patients (51%) underwent targeted next generation sequencing, and 19 of 22 (86%) had at least one pathogenic mutation, including mutations in MAPK pathway genes (73%). The median overall survival (OS) among the entire cohort was 16 months (95% CI: 8-50). The outcomes of those with multifocal disease were significantly shorter than their unifocal counterpart: median OS of 10 months versus 50 months (p = .07). Patients with risk organ involvement (bone marrow, spleen, or liver) had significantly inferior outcomes. Chemotherapy and surgery were the most common first-line treatments for multifocal and unifocal disease, respectively. While the outcome for patients with multifocal disease was poor, there was a subset of patients who had durable responses to treatment. Our study highlights that MH has heterogeneous clinical presentation, frequent oncogenic mutations, and prognosis, which is strongly tied to disease extent and type of organ involvement.

Long-term outcomes among adults with Langerhans cell histiocytosis

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

BRAF V600E is associated with higher incidence of second cancers in adults with Langerhans cell histiocytosis

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.

FDG PET/CT and thyroid biopsy leads to neurosarcoidosis diagnosis

We present a unique case of neurosarcoidosis diagnosed based on thyroid biopsy and FDG PET (Fluorodeoxyglucose positron emission tomography) imaging. A patient presented for a second opinion after being placed in hospice for rapidly progressing dementia, presumed to be due to Creutzfeldt Jakob disease despite negative workup and was unable to perform activities of daily life or communicate with his wife. The patient underwent a workup including whole-body FDG PET, which showed hypermetabolic lymph nodes as well as a hypermetabolic nodule in the thyroid. Biopsy of the lymph nodes was nondiagnostic, but the thyroid biopsy tissue yielded a diagnosis of sarcoid. After ruling out other causes and reviewing the tissue pathology, the patient was diagnosed with systemic sarcoidosis with neurological involvement and started on infliximab with rapid improvement.

Malignant Histiocytosis Comprises a Phenotypic Spectrum That Parallels the Lineage Differentiation of Monocytes, Macrophages, Dendritic Cells, and Langerhans Cells

Malignant histiocytoses (MHs), or the 'M group' of the Histiocyte Society classification, are characterized by neoplastic histiocytes with large pleomorphic nuclei. MH encompasses the diagnoses of histiocytic sarcoma, interdigitating dendritic cell sarcoma, and Langerhans cell sarcoma. We aimed to define the phenotypic spectrum of MH and examine the genotypic features across this spectrum. Using immunohistochemistry, we arranged the 22 cases into 4 subtypes that correspond to the lines of differentiation from monocytic and dendritic cell precursors as follows: (1) macrophage (n = 5): CD68+, CD163+, CD14+, and Factor 13a+; (2) monocyte-macrophage (n = 5): CD68+, CD163+, CD14+, S100+, and OCT2+; (3) dendritic cell (n = 6): CD68+, CD11c+, S100+, lysozyme+, ZBTB46+, and CD1a/langerin < 5%; and (4) Langerhans cell (n = 6): CD68+, CD11c+, S100+, ZBTB46+, CD1a+, and langerin+. The phenotypic subtypes align with those seen in low-grade histiocytic neoplasms as follows: MH-macrophage type correlates with Erdheim-Chester disease phenotype; MH-monocyte-macrophage type with Rosai-Dorfman disease phenotype, and MH-Langerhans cell type with Langerhans cell histiocytosis. Activating mutations in MAPK-pathway genes were identified in 80% of MH cases; 29% had mutations in the PI3k-AKT-mTOR pathway and 59% had mutations in epigenetic modulating genes. Strong expression of cyclin D1 was present in all cases, whereas p-ERK and p-AKT were not uniformly expressed. Eight of 22 (36%) MH cases were proven to be clonally related to a prior B-cell lymphoma. Defining the phenotypic spectrum of MH provides a guide to diagnosis and allows further exploration into the potential biological and clinical significance.

Metabolic PET/CT analysis of aggressive Non-Hodgkin lymphoma prior to Axicabtagene Ciloleucel CAR-T infusion: predictors of progressive disease, survival, and toxicity

PET/CT is used to evaluate relapsed/refractory non-Hodgkin lymphoma (NHL) prior to chimeric antigen receptor T-cell (CAR-T) infusion at two time points: pre-leukapheresis (pre-leuk) and pre-lymphodepletion chemotherapy (pre-LD). We hypothesized that changes in PET/CT between these time points predict outcomes after CAR-T. Metabolic tumor volume (MTV), total lesion glycolysis (TLG), and other metrics were calculated from pre-leuk and pre-LD PET/CT scans in patients with NHL who received axicabtagene ciloleucel, and assessed for association with outcomes. Sixty-nine patients were analyzed. While single time point PET/CT characteristics were not associated with risk of PD or death, increases from pre-leuk to pre-LD in parenchymal MTV, nodal MTV, TLG of the largest lesion, and total number of lesions were associated with increased risk of death (p < 0.05 for all). LASSO analysis identified increasing extranodal MTV and increasing TLG of the largest lesion as strong predictors of death (AUC 0.74). Greater pre-LD total MTV was associated with higher risk of grade 3+ immune effector cell-associated neurotoxicity syndrome (ICANS) (p = 0.042). Increasing metabolic disease burden during CAR-T manufacturing is associated with increased risk of progression and death. A two variable risk score stratifies prognosis prior to CAR-T infusion and may inform risk-adapted strategies.

Neurological Manifestations of Histiocytic Disorders

PURPOSE OF REVIEW

Histiocytic disorders, including Erdheim-Chester disease (ECD), Langerhans cell histiocytosis (LCH), and Rosai-Dorfman disease (RDD), are rare neoplasms that may present with a spectrum of neurologic involvement. Diagnostic delay is common due to heterogeneity in presentation and challenging pathology.

RECENT FINDINGS

Recent advances in the treatment of these diseases targeted towards mutations in the MAP kinase pathway have led to an improved prognosis in these patients with neurologic involvement. It is critical for clinicians to have a high index of suspicion to allow for early targeted treatment and optimize neurologic outcomes. A systematic approach to diagnosis is presented in this article to allow for accurate diagnosis of these rare diseases.

Technologist-Based Implementation of Total Metabolic Tumor Volume into Clinical Practice

Metabolic tumor volume (MTV) is defined as the total metabolically active tumor volume seen on ¹⁸F-FDG PET/CT examinations. Calculating MTV is often time-consuming, requiring a high degree of manual input. In this study, the MTV calculations of a board-certified nuclear radiologist were compared with those of 2 nuclear medicine technologists. As part of the technologists' educational program, after their classroom time they were trained by the radiologist for 30 min. The technologists calculated MTV within 7.5% of the radiologist's calculations in a set of patients who had diffuse large B-cell lymphoma and were undergoing initial staging ¹⁸F-FDG PET/CT. These findings suggest that nuclear medicine technologists may help accelerate implementation of MTV into clinical practice with favorable accuracy, possibly as an initial step followed by validation by the interpreting physician. The aim of this study was to explore whether efficiency is improved by integrating nuclear medicine technologists into a semiautomated workflow to calculate total MTV.

Bayesian penalized likelihood PET reconstruction impact on quantitative metrics in diffuse large B-cell lymphoma

Evaluate the quantitative, subjective (Deauville score [DS]) and reader agreement differences between standard ordered subset expectation maximization (OSEM) and Bayesian penalized likelihood (BPL) positron emission tomography (PET) reconstruction methods. A retrospective review of 104 F-18 fluorodeoxyglucose PET/computed tomography (CT) exams among 52 patients with diffuse large B-cell lymphoma. An unblinded radiologist moderator reviewed both BPL and OSEM PET/CT exams. Four blinded radiologists then reviewed the annotated cases to provide a visual DS for each annotated lesion. Significant (P < .001) differences in BPL and OSEM PET methods were identified with greater standard uptake value (SUV) maximum and SUV mean for BPL. The DS was altered in 25% of cases when BPL and OSEM were reviewed by the same radiologist. Interobserver DS agreement was higher for OSEM (>1 cm lesion = 0.89 and ≤1 cm lesion = 0.84) compared to BPL (>1 cm lesion = 0.85 and ≤1 cm lesion = 0.81). Among the 4 readers, average intraobserver visual DS agreement between OSEM and BPL was 0.67 for lesions >1cm and 0.4 for lesions ≤1 cm. F-18 Fluorodeoxyglucose PET/CT of diffuse large B-cell lymphoma reconstructed with BPL has higher SUV values, altered DSs and reader agreement when compared to OSEM. This report finds volumetric PET measurements such as metabolic tumor volume to be similar between BPL and OSEM PET reconstructions. Efforts such as adoption of European Association Research Ltd accreditation should be made to harmonize PET data with an aim at balancing the need for harmonization and sensitivity for lesion detection.

Ophthalmologic Involvement in Adults with Histiocytic Disorders: Clinical Presentation and Treatment Outcomes

PURPOSE

To evaluate the clinical presentation, treatment, and outcomes in adult patients with histiocytic disorders with ocular, orbital, optic nerve, or cavernous sinus involvement.

DESIGN

Observational, retrospective chart review.

PARTICIPANTS

Adult patients (age ≥ 18 years) at Mayo Clinic from January 1, 1996, to July 1, 2021, with histiocytic disorders. Inclusion criteria were (1) histiocytic disorder by biopsy and appropriate clinical phenotype; (2) available medical records; and (3) ocular, orbital, optic nerve, or cavernous sinus involvement.

METHODS

Retrospective chart review.

MAIN OUTCOME MEASURES

Response to therapy, measured in clinical and radiographic impact.

RESULTS

Thirty-two patients were identified: 7 with Langerhans cell histiocytosis (LCH); 15 with Erdheim-Chester disease (ECD); 1 with mixed LCH/ECD phenotype; 8 with Rosai-Dorfman disease (RDD); and 1 with mixed RDD/ECD phenotype. Ophthalmologic involvement was part of the initial presentation in 69% of patients (22/32). Eyelid edema (13/32, 41%) and proptosis (12/32, 38%) were the most frequent presentations. Isolated orbital or cavernous sinus involvement was present in 3 of 7 patients with LCH and 1 of 8 patients with RDD. Optic nerve sheath involvement was present in 2 of 7 LCH patients, 14 of 15 ECD patients, and 1 RDD/ECD patient. Diffuse (> 75%) orbital involvement was seen in 12 of 15 ECD patients and 1 of 7 LCH patients. Ocular involvement was seen in 1 of 15 ECD patients, 6 of 8 RDD patients, and 1 of 1 mixed RDD/ECD patient. The cavernous sinuses were involved in 1 of 7 LCH patients, 5 of 15 ECD patients, and both mixed phenotype patients. Visual acuity was affected in 14 patients (14/24, 58%) with a median logarithm of the minimum angle of resolution visual acuity of 0.1 (range, -0.12 to 3). BRAF V600E mutations were found in 75% (3/4) of LCH patients and 91% (10/11) of ECD patients. Patients received a variety of treatment, and response was variable across disease types.

CONCLUSIONS

Orbital involvement was more commonly seen in LCH and ECD, whereas ocular involvement was more common in RDD. Visual acuity may be impacted from ocular involvement or compression of the optic nerve with diffuse orbital involvement.

End-of-treatment PET in early-stage Hodgkin lymphoma: valuable in addition to interim-PET

Not available.

Sirolimus as frontline therapy for PTEN-mutated histiocytic sarcoma

Not available.

Outcomes After Treatment With Cobimetinib in Patients With Rosai-Dorfman Disease Based on KRAS and MEK Alteration Status

Importance

Rosai-Dorfman disease (RDD) is a rare histiocytic neoplasm with recent studies showing alterations in the MAPK pathway, most commonly in the KRAS and MEK genes in about 40% of patients. Reports on the use of MEK-inhibitor therapy in RDD have been limited to small case studies. There are no approved treatments for this neoplasm, and therefore patients with RDD need efficacious treatments.

Objective

To study the outcomes after treatment with cobimetinib based on MAPK pathway alterations in patients with RDD.

Design, Setting, and Participants

This retrospective cohort study conducted at 2 tertiary care centers included patients with RDD who underwent treatment with cobimetinib between January 1, 2013, and December 1, 2021. Cobimetinib was administered at a dosage of 20 to 60 mg orally once daily as a single agent for 21 days in a 28-day cycle. Pathology was centrally reviewed. Response assessment was centrally conducted and was based on the established positron emission radiography response criteria used for clinical trials of targeted therapies in histiocytosis.

Main Outcomes and Measures

Main outcomes were overall response rate (ORR), progression-free survival (PFS), adverse events (AEs) of cobimetinib in the entire cohort, and ORRs and PFS based on MAPK pathway alterations in patients with RDD.

Results

A total of 16 patients (median [range] age at cobimetinib initiation, 57 [31-74] years; 11 [69%] women) were included in the study. The median follow-up duration was 19.0 months (95% CI, 8.4-27.8 months). The ORR was 63% (n = 10), including 5 complete responses and 5 partial responses. Somatic alterations in the KRAS or MEK genes were detected in 8 (50%) patients. Patients with KRAS or MEK alterations had significantly higher ORR (88% vs 38%; P = .03), deeper responses (complete responses among responders: 71% vs 0%; P = .002), and better PFS (at 1 year, 100% vs 29% were free from progression or death, respectively; P < .001) compared with those without such alterations. Grade 2 or higher AEs occurred in 12 (75%) patients, and 9 (56%) required dose reduction or temporary/permanent treatment discontinuation due to AEs.

Conclusions and Relevance

In this cohort study, treatment with cobimetinib was associated with positive outcomes in KRAS- or MEK-variant RDD. However, AEs requiring dose modifications were common.

Association of Incidental Positron Emission Tomography Uptake in the Esophagus to Gastroesophageal Reflux Disease

The Los Angeles (LA) classification is the most accurate means of assessing esophageal injury from caustic gastric acid with focused and greater concentrations in areas of erosive disease.¹ However, data from animal models and patients have proposed that an initial diffuse inflammatory pathway contributes to injury in gastroesophageal reflux disease (GERD) mediated by interleukin (IL) 8, IL1β,^2,3 and hypoxia-inducible factors.^4,5 These observations demonstrate a lymphocyte predominant inflammatory process over course of 1-2 weeks associated with basal zone hyperplasia and dilation of intercellular spaces.⁶ In cultured human esophageal epithelial cells and patients, it is further suggested that acid causes this chronic inflammatory reaction.

Combined modality therapy for early-stage Hodgkin lymphoma in the PET era: A real-world study

e19532

Background: The traditional approach to the treatment of early-stage classical Hodgkin lymphoma (cHL) has been combined modality therapy (CMT) with both chemotherapy and radiotherapy (RT). CMT has shown improved disease control, but RT can lead to long-term adverse effects, including secondary malignancies and cardiac toxicity. Multiple clinical trials have assessed treatment de-escalation strategies to chemotherapy-alone regimens, but results are conflicting. We aimed to assess the real-world implications of these trials by comparing patient outcomes based upon treatment with CMT or chemotherapy-alone. Furthermore, we proposed to assess differences in treatment outcomes stratified by disease bulk, favorable/unfavorable disease, and PET2 response. Methods: We conducted a retrospective, multi-center cohort study of consecutive adult patients with early-stage (stage IA-IIB) cHL treated between January 2010-December 2020. Baseline characteristics, treatment modality, and outcomes were abstracted by chart review. Available PET2 scans (n=110) were independently reviewed by a blinded nuclear radiologist. Deauville score (DS) ≥4 was characterized as positive (+), and DS≤3 negative (-). All analysis was conducted using intention-to-treat principles based upon the initial treatment plan (CMT or chemotherapy-alone). Results: In 125 patients [58% male, median age 34 (range, 18-78)] with early-stage cHL, CMT was intended in 63 (50%) patients, with chemotherapy-alone in 62 (50%). Bulky disease was observed in 43 (34%), unfavorable disease in 81 (65%), and 15 (14%) were found to be PET2+. With median follow-up of 59.8 months (95%CI, 48.6 to 71.0), 5 (4%) deaths occurred, and 17 (14%) patients had relapsed/refractory disease. No significant differences in overall survival (OS) were seen based upon treatment intention. However, there was substantially reduced progression-free survival (PFS) (Table) with chemotherapy-alone in the whole cohort, and also in those with bulky, unfavorable, and PET2+ disease. No significant PFS differences were seen based upon treatment intention for patients with non-bulky, favorable, or PET2- disease. Conclusions: Based on our real-world experience, CMT appears particularly beneficial for patients with bulky disease, unfavorable prognostic factors, and PET2+ disease. However, while recent trials showed a benefit of CMT in non-bulky, favorable and PET2- patients, chemotherapy-alone may be comparable for these patients in actual clinical practice.[Table: see text]

PET2 response associated with survival in newly diagnosed diffuse large B-cell lymphoma: results of two independent prospective cohorts

Studies evaluating Positron Emission Tomography scan after 2 cycles of chemotherapy (PET2) in newly diagnosed diffuse large B cell lymphoma (DLBCL) are heterogeneous in patient characteristics, treatments and have conflicting results. Here we report association of PET2 with outcomes in two large independent prospective cohorts of newly diagnosed DLBCL pts treated with two RCHOP-based regimens. The discovery cohort consisted of pts enrolled in single arm phase 2 MC078E study of lenalidomide with RCHOP (R2CHOP). The validation cohort consisted of RCHOP-treated pts from the Molecular Epidemiology Resource (MER) cohort. Pts who received 3-6 cycles of therapy and had PET2 were included in the study. Patients who progressed on PET2 were excluded. Revised response criteria 2007 were used to define PET2 response PET2 positive (PET2 + ) pts had inferior EFS [24-month EFS 45.5% vs 87.9%, HR 4.0, CI₉₅ (2.1-7.9), p < 0.0001) with a trend towards lower OS [24-months OS 77% vs 94.8%, HR 2.0, CI₉₅ (0.9-4.8), P = 0.1] than PET2 negative (PET2-) pts in MC078E cohort. PET2 + pts had an inferior EFS (24 month EFS 48.7% vs 81.6%, HR 2.9, CI₉₅ 2.0-4.2, p < 0.0001) and OS (24-month OS 68.6% vs 88.1%, HR 2.3, CI₉₅: 1.5-3.5, p < 0.0001) in the MER cohort. These results were consistent regardless of age, sex and in the subgroup of advanced stage and high-risk international prognostic index (IPI). For MER, PET2 + pts also had higher odds of positive end of treatment PET (OR: 17.3 (CI₉₅ 7.9-37.7), p < 0.001). PET2 is an early predictor DLBCL pts at high risk of progression and death in two independent prospective cohorts. PET2-guided risk-adapted strategies may improve outcomes, and should be explored in clinical trials.

International expert consensus recommendations for the diagnosis and treatment of Langerhans cell histiocytosis in adults

Langerhans cell histiocytosis (LCH) can affect children and adults with a wide variety of clinical manifestations, including unifocal, single-system multifocal, single-system pulmonary (smoking-associated), or multisystem disease. The existing paradigms in the management of LCH in adults are mostly derived from the pediatric literature. Over the last decade, the discovery of clonality and MAPK-ERK pathway mutations in most cases led to the recognition of LCH as a hematopoietic neoplasm, opening the doors for treatment with targeted therapies. These advances have necessitated an update of the existing recommendations for the diagnosis and treatment of LCH in adults. This document presents consensus recommendations that resulted from the discussions at the annual Histiocyte Society meeting in 2019, encompassing clinical features, classification, diagnostic criteria, treatment algorithm, and response assessment for adults with LCH. The recommendations favor the use of 18F-Fluorodeoxyglucose positron emission tomography-based imaging for staging and response assessment in the majority of cases. Most adults with unifocal disease may be cured by local therapies, while the first-line treatment for single-system pulmonary LCH remains smoking cessation. Among patients not amenable or unresponsive to these treatments and/or have multifocal and multisystem disease, systemic treatments are recommended. Preferred systemic treatments in adults with LCH include cladribine or cytarabine, with the emerging role of targeted (BRAF and MEK inhibitor) therapies. Despite documented responses to treatments, many patients struggle with a high symptom burden from pain, fatigue, and mood disorders that should be acknowledged and managed appropriately.

Metabolic characteristics and prognostic differentiation of aggressive lymphoma using one-month post-CAR-T FDG PET/CT

BACKGROUND

F-18 fluorodeoxyglucose positron emission tomography computed tomography (PET/CT) is used to assess response of non-Hodgkin lymphoma (NHL) to chimeric antigen receptor T cell (CAR-T) therapy. We sought to describe metabolic and volumetric PET prognostic factors at one month post-CAR-T and identify which patients with partial response (PR) or stable disease (SD) are most likely to subsequently achieve complete response (CR), and which will develop progressive disease (PD) and death.

METHODS

Sixty-nine patients with NHL received axicabtagene ciloleucel CAR-T therapy. One-month post-CAR-T infusion and PET/CT scans were segmented with a fixed absolute SUV maximum (SUVMax) threshold of 2.5 using a semiautomated workflow with manual modification to exclude physiologic uptake as needed. Metabolic tumor volume (MTV), total lesion glycolysis (TLG), SUVMax, and other lesion characteristics were calculated and associated with risk of PD and death.

RESULTS

Patients with total MTV > 180 cc, presence of bone or parenchymal disease, SUVMax > 10, single lesion TLG > 245 g, or > 2 total lesions had increased risk of death. Patients with total MTV > 55 cc, total TLG > 250 cc, SUV Max > 10, or > 2 total lesions had increased risk of PD. For the subset of 28 patients with PR/SD, higher SUVMax was associated with increased risk of subsequent PD and death. While 86% of patients who had SUVMax ≥ 10 eventually had PD (HR 3.63, 1.13-11.66, p = 0.03), only 36% of those with SUVMax < 10 had PD.

CONCLUSIONS

Higher SUVMax at one month post-CAR-T is associated with higher risk of PD and death. SUVMax ≥ 10 may be useful in guiding early salvage treatment decisions in patients with SD/PR at one month.

Sustained, complete response to pexidartinib in a patient with CSF1R-mutated Erdheim-Chester disease

Erdheim-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 (CSF1R^{R549_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.

OUP accepted manuscript

Introduction

Materials and Methods

Results

Conclusion

Safety and Efficacy of Percutaneous Image-Guided Mediastinal Mass Core-Needle Biopsy

Objective

To retrospectively evaluate the safety and efficacy of percutaneous image-guided mediastinal mass core-needle biopsy.

Patients and Methods

Retrospective review of an institutionally maintained biopsy registry identified 337 computed tomography- or ultrasound-guided percutaneous mediastinal mass core needle biopsies between October 2002 and August 2017 in a single quaternary referral center. Mean patient age was 51 (range, 18 to 93) years. Procedural techniques, anticoagulation/antiplatelet therapy, and tumor anatomical characteristics were reviewed. Classification and gradation of complications was based on the Clavien-Dindo system. Diagnostic yield was defined as the ratio of diagnostic biopsy to all biopsies performed.

Results

Mean tumor size was 59.2 (range, 10 to 180) mm with 89.9% (n=303) of lesions located in the prevascular (anterior) mediastinum. There was a single major complication (0.3%) of a symptomatic pneumothorax requiring intervention. There were seven (2.1%) minor complications, including three bleeding complications. A transpleural approach was the only variable associated with an increased complication rate (P<.01). Forty-one (12.2%) patients had a biopsy performed while taking an antiplatelet/anticoagulant agent within the therapeutic window, with a single case (0.3%) associated with a minor bleeding complication. Of 18 (5.3%) procedures performed without cessation of anticoagulant/antiplatelet therapy, there were no bleeding complications. Of all 337 biopsies, 322 (95.5%) were diagnostic. None of the analyzed variables were significantly associated with a nondiagnostic biopsy.

Conclusion

Image-guided percutaneous core-needle biopsy of mediastinal masses is a safe procedure with high diagnostic yield. Further prospective studies are required to assess the complication profile in higher risk patients.

Langerhans cell histiocytosis with lung involvement in isolation and multisystem disease: Staging, natural history, and comparative survival

Langerhans cell histiocytosis (LCH) is a histiocytic neoplasm that can involve the lungs as single system (LCH-SSL) or multisystem disease (LCH-MSL). The role of full-body radiographic staging to determine whether patients have LCH-SSL or LCH-MSL is unclear. Long-term outcomes of LCH-SSL versus LCH-MSL and multisystem without lung involvement (LCH-MSNL) are unknown. A retrospective study of adult LCH patients seen at our center from January 2000 to 2020 was performed. In Part 1, we addressed utility of whole-body staging imaging among those presenting with isolated pulmonary signs or symptoms. Staging was defined as fluorodeoxyglucose positron emission tomography-computed tomography (CT) or whole-body CT obtained within 3 months of diagnosis. In Part 2, we examined the frequency of developing extra-pulmonary disease over time and mortality in patients with LCH-SSL. In Part 3, we compared the overall survival of LCH-SSL, LCH-MSL, and LCH-MSNL. Part 1: 240 patients with LCH were identified. A total of 112 (47%) had pulmonary signs or symptoms at presentation. Thirty-four (30%) underwent radiographic staging and only one showed evidence of extra-pulmonary disease. Part 2: 108 (45%) were LCH-SSL. Median follow-up duration of 4.5 years (95% confidence interval [CI]: 2.9-6.0). None developed extra-pulmonary disease. Part 3: 5-year survival: 94% (95% CI: 84%-98%) for LCH-SSL, 78% (95% CI: 59%-90%) for LCH-MSL, and 75% (95% CI: 53%-89%) for LCH-MSNL. LCH patients presenting with isolated pulmonary signs or symptoms rarely have extra-pulmonary involvement at the time of diagnosis and generally do not develop extra-pulmonary progression. LCH-SSL has the best overall survival, while LCH-MSL and LCH-MSNL have similar clinical outcomes.

Mimics of Erdheim-Chester disease

Erdheim-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.

Phenotypes and prognostic factors in adults with Langerhans cell histiocytosis

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]

BRAFV600E frequency and impact on outcomes in adults with langerhans cell histiocytosis

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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]

How We Do It: A Multidisciplinary Approach to 177Lu DOTATATE Peptide Receptor Radionuclide Therapy

Lutetium 177 (¹⁷⁷Lu) DOTA-0-Tyr3-Octreotate (DOTATATE) peptide receptor radionuclide therapy (PRRT) is an effective treatment for advanced gastroenteropancreatic neuroendocrine tumors. This review presents a clinical practice workflow that has been successful since ¹⁷⁷Lu DOTATATE PRRT was approved by the U.S. Food and Drug Administration. The workflow relies heavily on the input of a multidisciplinary team and involves a nuclear medicine consultation service, tumor board, and specific preparations in advance of therapy and day-of-therapy procedures. A systematic checklist designed to ensure appropriate selection of treatment candidates and identification of any concerns to address to safely administer PRRT is provided. All patients were evaluated with gallium 68 DOTATATE PET/CT, and in cases of high-grade tumors, they were also evaluated with fluorine 18 fluorodeoxyglucose PET/CT, with imaging findings reviewed as part of the systematic checklist before PRRT. Adverse effects are discussed and imaging follow-up regimens are reviewed, including alternative diagnostic contrast materials. Approaches to multiple challenging patient scenarios are illustrated through case examples. Finally, alternative theranostic radionuclides and treatment strategies are discussed.

Thoracic positron emission tomography: 18F-fluorodeoxyglucose and beyond

Ongoing technologic and therapeutic advancements in medicine are now testing the limits of conventional anatomic imaging techniques. The ability to image physiology, rather than simply anatomy, is critical in the management of multiple disease processes, especially in oncology. Nuclear medicine has assumed a leading role in detecting, diagnosing, staging and assessing treatment response of various pathologic entities, and appears well positioned to do so into the future. When combined with computed tomography (CT) or magnetic resonance imaging (MRI), positron emission tomography (PET) has become the sine quo non technique of evaluating most solid tumors especially in the thorax. PET/CT serves as a key imaging modality in the initial evaluation of pulmonary nodules, often obviating the need for more invasive testing. PET/CT is essential to staging and restaging in bronchogenic carcinoma and offers key physiologic information with regard to treatment response. A more recent development, PET/MRI, shows promise in several specific lung cancer applications as well. Additional recent advancements in the field have allowed PET to expand beyond imaging with ¹⁸F-flurodeoxyglucose (FDG) alone, now with the ability to specifically image certain types of cell surface receptors. In the thorax this predominantly includes ⁶⁸Ga-DOTATATE which targets the somatostatin receptors abundantly expressed in neuroendocrine tumors, including bronchial carcinoid. This receptor targeted imaging technique permits targeting these tumors with therapeutic analogues such as ¹⁷⁷Lu labeled DOTATATE. Overall, the proper utilization of PET in the thorax has the ability to directly impact and improve patient care.

Efficacy of BRAF-Inhibitor Therapy in BRAFV600E -Mutated Adult Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare histiocytic neoplasm. To date, there is a lack of U.S. Food and Drug Administration-approved treatments in adult LCH to establish optimal first-line therapy. We conducted a retrospective, single-center case series evaluating the use of BRAF inhibitors in adult patients with BRAF^V600E - LCH proven by biopsy. Our case series is the first to report the use of BRAF inhibitors as first-line therapy in adults with LCH. We also report the efficacy with single-agent dabrafenib in adult LCH. All but one of our patients had favorable response to targeted therapy.

Analysis and impact of a multidisciplinary lymphoma virtual tumor board

The aim is to prospectively evaluate the impact of a multidisciplinary lymphoma virtual tumor board. The utility of multi-site interactive lymphoma-specific tumor boards has not been reported. The Mayo Clinic Lymphoma Tumor Board is a component of the International Mayo Clinic Care Network (MCCN). The format includes the clinical case presentation, presentation of radiology and hematopathology findings by the appropriate subspecialist, proposed treatment options, review of the literature pertinent to the case, pharmacy contributions, and discussion followed by recommendations. Three hundred and nine consecutive highly selected real-time cases with a diagnosis of lymphoma were presented at the Mayo Clinic Lymphoma Tumor Board from January 2014 to June 2018 and decisions were prospectively tracked to assess its impact on the treatment decisions. A total of 309 cases were prospectively evaluated. One hundred and forty (45.3%) cases had some changes made or recommended. The total changes suggested were 179, as some cases had more than one recommendation. There were 93 (30%) clinical management recommendations, 45 (14.6%) additional testing recommendations, 29 (9.4%) pathology changes, and 6 (1.9%) radiology changes. In an electronic evaluation process, 93% of the responders reported an improvement in knowledge and competence, and 100% recommended no change in format of the board. A multidisciplinary lymphoma tumor board approach was found to have a meaningful impact on lymphoma patients while enhancing interdisciplinary interactions and education for multiple levels of the clinical care team.

Unusual manifestations of diffuse-type tenosynovial giant cell tumor in two patients: importance of radiologic-pathologic correlation

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a rare, locally aggressive neoplasm. It most commonly occurs in the knee, followed by the hip, and has distinctive imaging features, including mass-like foci of low T2 signal intensity, "blooming" on gradient-echo MRI, and pronounced uptake on FDG PET/CT. Histologically, TSGCT demonstrates a neoplastic population of mononuclear cells admixed with hemosiderin-laden macrophages, foamy histiocytes, inflammatory cells, and osteoclast-like giant cells. In cases where diffuse-type TSGCT presents in an uncommon location or with atypical features, the imaging diagnosis may be challenging. Furthermore, because of its polymorphous appearance, it may be mistaken microscopically for other neoplastic and non-neoplastic histiocytic lesions. Herein, we present two cases of diffuse-type TSGCT presenting as large masses, and underscore the importance of radiologic-pathologic correlation for accurate diagnosis.

Clinicopathological features, treatment approaches, and outcomes in Rosai-Dorfman disease

Rosai-Dorfman disease is a rare subtype of non-Langerhans cell histiocytosis. With the last major report published in 1990, there is a paucity of contemporary data on this disease. Our objective was to report the clinicopathological features, treatments and outcomes of patients seen at a tertiary referral center. Sixty-four patients with histopathological diagnosis of Rosai-Dorfman disease were identified from 1994 to 2017 (median age 50 years; range, 2-79). The median duration from symptom onset to diagnosis was seven months (range, 0-128), which was also reflected in the number of biopsies required to establish the diagnosis (median 2; range, 1-6). The most common presentation was subcutaneous masses (40%). Of the 64 patients, 8% had classical (nodal only) and 92% had extra-nodal disease (67% extra-nodal only). The most common organs involved were skin and subcutaneous tissue (52%), followed by lymph nodes (33%). Three patients had an overlap with Erdheim-Chester disease, which had not been described before. Two of these were found to have MAP2K1 mutations. Commonly utilized first line treatments were surgical excision (38%) and systemic corticosteroids (27%). Corticosteroids led to a response in 56% of the cases. Of those treated initially, 15 (30%) patients developed recurrent disease. The most commonly used systemic agent was cladribine (n=6), with 67% overall response rate. Our study demonstrates that Rosai-Dorfman disease has diverse clinical manifestations and outcomes. While this disease has been historically considered a benign entity, a subset of patients endures an aggressive course necessitating the use of systemic therapies.

Psi Chi Online Video Resources

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The Mayo Clinic Histiocytosis Working Group Consensus Statement for the Diagnosis and Evaluation of Adult Patients With Histiocytic Neoplasms: Erdheim-Chester Disease, Langerhans Cell Histiocytosis, and Rosai-Dorfman Disease

Histiocytic neoplasms, a rare and heterogeneous group of disorders, primarily include Erdheim-Chester disease, Langerhans cell histiocytosis, and Rosai-Dorfman disease. Due to their diverse clinical manifestations, the greatest challenge posed by these neoplasms is the establishment of a diagnosis, which often leads to a delay in institution of appropriate therapy. Recent insights into their genomic architecture demonstrating mitogen-activated protein kinase/extracellular signal-regulated kinase pathway mutations have now enabled potential treatment with targeted therapies in most patients. This consensus statement represents a joint document from a multidisciplinary group of physicians at Mayo Clinic who specialize in the management of adult histiocytic neoplasms. It consists of evidence- and consensus-based recommendations on when to suspect these neoplasms and what tests to order for the diagnosis and initial evaluation. In addition, it also describes the histopathologic and individual organ manifestations of these neoplasms to help the clinicians in identifying their key features. With uniform guidelines that aid in identifying these neoplasms, we hope to improve the awareness that may lead to their timely and correct diagnosis.

Radiolocalization of atypical lesions for intraoperative identification: technical factors, localization quality, success rates, patient safety, and spectrum of applications

Background

To retrospectively analyze perilesional technetium Tc-99m MAA injection for intraoperative localization of atypical soft-tissue and bone lesions within a single tertiary referral center in order to determine technique, safety, and clinical utility of these procedures.

Methods

An IRB compliant, retrospective electronic chart review (2010–2017) exploring surgical excision of atypical (non-pulmonary, non-breast, non-sentinel node) lesions guided by Tc-99m MAA perilesional injection. Patient demographics, lesion location, lesion size, radiotracer injection technique, radiotracer injection complications, scintigraphy technique, scintigraphic quality, intraoperative time, lesion identification in surgery, and pathological diagnoses were recorded.

Results

Twenty-two atypical radiolocalization exams were identified. Lesion sites included rib (7), lymph node (4), abdominal wall (3), mesenteric (3), gallbladder fossa (1), retroperitoneum (1), parietal pleura (1), anterior mediastinum (1), and iliac bone (1). Average lesion size was 14 mm (range 5–23 mm). Eighteen (82%) radiotracer injections used computed tomography guidance and 4 (18%) used ultrasound guidance. The mean activity of Tc-99m MAA administered was 11.8 MBq (0.32 mCi). A 22-gauge needle was most often used for perilesional injection. No injection complications were reported. The lesions were identified with a hand-held gamma probe during surgery in 100% of cases. Of the samples sent to pathology, 100% were identified and given a diagnosis.

Conclusion

Radiolocalization of atypical lesions may be a valuable technique, guiding minimally invasive surgical removal of lesions that would otherwise be difficult to identify intraoperatively such as non-palpable rib, central mesenteric nodal, and abdominal wall lesions.

Adult Langerhans cell histiocytosis: A contemporary single-institution series of 186 patients

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Background: Langerhans cell histiocytosis (LCH) is a rare histiocytic neoplasm driven by MAPK-ERK mutations in majority of patients. Contemporary data on treatments and outcomes in adult LCH are lacking. Hence, we undertook this study to analyze a large cohort of adult LCH patients. Methods: This was a retrospective study of adult (≥18 years) LCH patients seen at our institution between 1998 and 2018. Results: We included 186 patients with adult LCH (median age 43; 19-88), and 54% were females. 70% of patients were diagnosed after 2007. Common presenting symptoms were cough/dyspnea (30%), rash (17%), pain/swelling in head (17%), and diabetes insipidus (10%). 70 (38%) patients had multisystem LCH, 62 (33%) had isolated pulmonary LCH, and 35 (19%) had unifocal LCH. Common sites of involvement included lung (59%), bone (37%), skin (21%), and nervous system (16%). 121 (65%) were smokers; 48% of these had lung disease, while 52% had multisystem disease. 18 of 31 tested (58%) patients had BRAF-V600E mutation. Most common first-line treatment was smoking cessation in 24 patients, and led to an overall response rate (ORR) of 83% in pulmonary lesions. Radiation therapy was used in 11 patients, and led to an ORR 82%. Surgical resection of lesion was done in 23 patients, with relapses in 24%. Systemic therapies were used in 78 (42%) patients (Table). Most common first-line systemic therapy was cladribine with ORR of 78%. Vemurafenib was used in 3 patients with BRAF-V600E, leading to an ORR of 67% . After a median follow-up of 23 months (0-261), 21 patients had died. Of these, 10 died of progressive LCH. Median OS was not reached, and mean OS was 196 months. Conclusions: This is the largest contemporary series of adult LCH. It shows that diverse clinical spectrum, ranging from benign course to a progressive multisystem disease. Although smoking cessation was an effective treatment for pulmonary LCH, a large subset required systemic chemotherapy. [Table: see text]

Rheumatoid pulmonary nodules: clinical and imaging features compared with malignancy

OBJECTIVES

The objective of this study was to identify clinical and imaging features that distinguish rheumatoid lung nodules from malignancy.

METHODS

We conducted a retrospective review of 73 rheumatoid patients with histologically-proven rheumatoid and malignant lung nodules encountered at Mayo Clinic, Rochester, MN (2001-2016). Medical records and imaging were reviewed including a retrospective blinded review of CT and PET/CT studies.

RESULTS

The study cohort had a mean age of 67 ± 11 years (range 45-86) including 44 (60%) women, 82% with a smoking history, 38% with subcutaneous rheumatoid nodules, and 78% with rheumatoid factor seropositivity. Subjects with rheumatoid lung nodules compared to malignancy were younger (59 ± 12 vs 71 ± 9 years, p < 0.001), more likely to manifest subcutaneous rheumatoid nodules (73% vs 20%, p < 0.001) and rheumatoid factor seropositivity (93% vs 68%, p = 0.034) but a history of smoking was common in both groups (p = 0.36). CT features more commonly associated with rheumatoid lung nodules compared to malignancy included multiplicity, smooth border, cavitation, satellite nodules, pleural contact, and a subpleural rind of soft tissue. Optimal sensitivity (77%) and specificity (92%) (AUC 0.85, CI 0.75-0.94) for rheumatoid lung nodule were obtained with ≥ 3 CT findings (≥ 4 nodules, peripheral location, cavitation, satellite nodules, smooth border, and subpleural rind). Key ¹⁸FDG-PET/CT features included low-level metabolism (SUV_max 2.7 ± 2 vs 7.2 ± 4.8, p = 0.007) and lack of ¹⁸F-fluorodeoxyglucose (FDG)-avid draining lymph nodes.

CONCLUSION

Rheumatoid lung nodules have distinct CT and PET/CT features compared to malignancy. Patients with rheumatoid lung nodules are younger and more likely to manifest subcutaneous rheumatoid nodules and seropositivity.

KEY POINTS

• Rheumatoid lung nodules have distinct clinical and imaging features compared to lung malignancy. • CT features of rheumatoid lung nodules include multiplicity, cavitation, satellite nodules, smooth border, peripheral location, and subpleural rind. • Key PET/CT features include low-level metabolism and lack of FDG-avid draining lymph nodes.

Gadolinium Deposition within the Pediatric Brain: No Increased Intrinsic T1-Weighted Signal Intensity within the Dentate Nucleus following the Administration of a Minimum of 4 Doses of the Macrocyclic Agent Gadoteridol

BACKGROUND AND PURPOSE

Our aim was to evaluate whether serial administration of the macrocyclic gadolinium-based contrast agent gadoteridol in children is associated with T1-weighted hyperintensity within the dentate nucleus, an imaging surrogate for gadolinium deposition.

MATERIALS AND METHODS

We identified a retrospective cohort of 10 patients younger than 18 years of age who underwent between 4 and 8 gadoteridol-enhanced MR imaging examinations of the brain from 2016 to 2017. For comparison, we identified a retrospective cohort of 9 pediatric patients who each underwent 6 gadodiamide-enhanced MR imaging examinations. For each examination, both dentate nuclei were contoured on unenhanced images and the mean dentate-to-pons signal intensity ratio was calculated. Dentate-to-pons signal intensity ratios from the first and last scans were compared using paired t tests.

RESULTS

In the gadoteridol group, there was no significant change in the mean dentate-to-pons signal intensity ratio from the first to the last scan (0.99 versus 0.99, P = .59). In the gadodiamide group, there was a significant increase in the mean dentate-to-pons signal intensity ratio from the first to the last scan (0.99 versus 1.10, P = .001).

CONCLUSIONS

Repeat administration of the macrocyclic gadolinium-based contrast agent gadoteridol in children was not associated with T1-weighted dentate hyperintensity, while the repeat administration of the linear gadolinium-based contrast agent gadodiamide was associated with T1-weighted dentate hyperintensity, presumably due to gadolinium deposition.