Aberrant paracrine signalling for bone remodelling underlies the mutant histone-driven giant cell tumour of bone

Oncohistones represent compelling evidence for a causative role of epigenetic perturbations in cancer. Giant cell tumours of bone (GCTs) are characterised by a mutated histone H3.3 as the sole genetic driver present in bone-forming osteoprogenitor cells but absent from abnormally large bone-resorbing osteoclasts which represent the hallmark of these neoplasms. While these striking features imply a pathogenic interaction between mesenchymal and myelomonocytic lineages during GCT development, the underlying mechanisms remain unknown. We show that the changes in the transcriptome and epigenome in the mesenchymal cells caused by the H3.3-G34W mutation contribute to increase osteoclast recruitment in part via reduced expression of the TGFβ-like soluble factor, SCUBE3. Transcriptional changes in SCUBE3 are associated with altered histone marks and H3.3^G34W enrichment at its enhancer regions. In turn, osteoclasts secrete unregulated amounts of SEMA4D which enhances proliferation of mutated osteoprogenitors arresting their maturation. These findings provide a mechanism by which GCTs undergo differentiation in response to denosumab, a drug that depletes the tumour of osteoclasts. In contrast, hTERT alterations, commonly found in malignant GCT, result in the histone-mutated neoplastic cells being independent of osteoclasts for their proliferation, predicting unresponsiveness to denosumab. We provide a mechanism for the initiation of GCT, the basis of which is dysfunctional cross-talk between bone-forming and bone-resorbing cells. The findings highlight the role of tumour/microenvironment bidirectional interactions in tumorigenesis and how this is exploited in the treatment of GCT.

Differential diagnosis of hip pain in children referred to a specialist bone tumour service

OBJECTIVE

To determine the differential diagnosis of bone lesions causing hip pain in children and the association between radiographic features of aggression and MRI appearances with final diagnosis.

METHODS

Retrospective review of children with hip pain referred to a specialist musculoskeletal oncology service between September 2018 and December 2020. Patient demographics, lesion location, the radiographic and MRI features, and the final diagnosis, which was made either by image-guided biopsy, surgical curettage or based on typical imaging features were recorded. Statistical analysis examined the association between the Lodwick-Madewell score (determined from available radiographs) and MRI findings with final diagnosis.

RESULTS

Fifty-nine patients were included, 40 males and 19 females with mean age 10.9 years, (range 3-16 years). Final diagnoses were based on histology in 24 (40.7%) cases and imaging in 35 (59.3%) cases. Eighteen lesions (30.5%) were classed as non-neoplastic, 31 (52.5%) as benign and 10 (16.9%) as malignant, of which four were primary bone sarcomas. There was a significant association between the Lodwick-Madewell score and final diagnosis (p < 0.001). On MRI, bone marrow oedema, presence of a focal lesion, bone expansion and the presence of an extraosseous mass were all significantly associated with final diagnostic classification.

CONCLUSION

The differential diagnosis of hip pain in children presenting to a bone tumour service is wide. Most cases are due to benign or non-neoplastic conditions, with only 10 out of 59 children having a malignant lesion. Radiography complemented by MRI plays a major role in differentiating non-neoplastic, benign neoplastic and malignant lesions and in determining the requirement for needle biopsy.

ADVANCES IN KNOWLEDGE

This is the first study to consider how imaging features relate to diagnosis in suspected paediatric hip tumours. Use of this information can help in determining which cases should undergo needle biopsy.

MRI for paediatric flatfoot: is it necessary?

OBJECTIVE

To determine the additional benefit of MRI for children with flatfoot deformity assessed with weight-bearing radiographs in a specialist paediatric orthopaedic unit.

METHODS AND MATERIALS

Patient cohort was obtained by searching the Radiology Information System for children referred for investigation of flatfoot. All patients with flatfoot on weight-bearing radiographs who had undergone MRI were included. Radiographs were classified by a consultant musculoskeletal radiologist as showing no underlying abnormality, talo-calcaneal coalition, calcaneonavicular coalition, accessory navicular or other abnormality. MRI studies were classified similarly by a different consultant musculoskeletal radiologist blinded to the radiographic findings.

RESULTS

33 males and 24 females were included (mean age 12.5 years; range 3-18 years). 24 had bilateral abnormality, so 81 feet were assessed. Radiographs showed no specific abnormality (n = 51), talocalcaneal coalition (n = 6), calcaneonavicular coalition (n = 3), os naviculare (n = 12) or other abnormality (n = 9). MRI showed no specific abnormality (n = 40), talocalcaneal coalition (n = 10), calcaneonavicular coalition (n = 5), os naviculare (n = 12) or other abnormality (n = 14). Assuming MRI as the diagnostic gold-standard, additional relevant diagnostic information was identified in 19 (23.5%) cases, while in the 51 cases for which radiographs provided no specific diagnosis MRI confirmed no underlying abnormality in 31 (60.8%).

CONCLUSION

MRI is a valuable adjunct to weight-bearing radiography for investigating paediatric flatfoot deformity.

ADVANCES IN KNOWLEDGE

MRI is of value in the assessment of paediatric flatfoot, additional diagnostic information to radiography being identified in 23.5% cases, while in 60.8% of cases for which radiographs provided no specific diagnosis MRI confirmed no underlying abnormality.

Circulating tumour DNA is a promising biomarker for risk stratification of central chondrosarcoma with IDH1/2 and GNAS mutations

Chondrosarcoma (CS) is a rare tumour type and the most common primary malignant bone cancer in adults. The prognosis, currently based on tumour grade, imaging and anatomical location, is not reliable, and more objective biomarkers are required. We aimed to determine whether the level of circulating tumour DNA (ctDNA) in the blood of CS patients could be used to predict outcome. In this multi-institutional study, we recruited 145 patients with cartilaginous tumours, of which 41 were excluded. ctDNA levels were assessed in 83 of the remaining 104 patients, whose tumours harboured a hotspot mutation in IDH1/2 or GNAS. ctDNA was detected pre-operatively in 31/83 (37%) and in 12/31 (39%) patients postoperatively. We found that detection of ctDNA was more accurate than pathology for identification of high-grade tumours and was associated with a poor prognosis; ctDNA was never associated with CS grade 1/atypical cartilaginous tumours (ACT) in the long bones, in neoplasms sited in the small bones of the hands and feet or in tumours measuring less than 80 mm. Although the results are promising, they are based on a small number of patients, and therefore, introduction of this blood test into clinical practice as a complementary assay to current standard-of-care protocols would allow the assay to be assessed more stringently and developed for a more personalised approach for the treatment of patients with CS.

Ossifying Fibroma of Non-odontogenic Origin: A Fibro-osseous Lesion in the Craniofacial Skeleton to be (Re-)considered

In the cranio-facial skeleton, a heterogeneous group of well characterized fibro-osseous lesions can be distinguished. Whereas fibrous dysplasia can affect any skeletal bone, ossifying fibroma and cemento-osseous dysplasia exclusively develop in the cranio-facial region, with most subtypes restricted to the tooth bearing areas of the jaws. Herein we present a series of 20 fibro-osseous lesions that developed mostly in the frontal bone and in the mandible, presenting as expansile intramedullary tumors with a unique histologic appearance and an indolent clinical course. We provide evidence that these tumors are distinct from the categories included in the WHO classification and are therefore currently unclassifiable. The definition of cemento-ossifying fibroma as an odontogenic neoplasm developing only in close proximity to teeth should be re-considered and incorporate also extragnathic lesions as shown here.

1001. HIV RNA monitoring after hospitalization for non-HIV-related illness in patients on combination antiretroviral therapy prior to admission

Background

Hospitalization presents risk for loss of virologic suppression (VS) in people living with HIV (PLWH) due to issues with combination antiretroviral therapy (cART). cART medication errors or drug-drug interactions with new maintenance medications may lead to loss of VS. Appropriate monitoring of HIV RNA post-discharge to ensure ongoing VS may not occur following non-HIV-related illnesses. The objective of this multi-center study was to describe HIV RNA monitoring and VS in PLWH following hospitalization for non-HIV-related illnesses.

Methods

PLWH at least 18 years old with a CD4 count &gt;200 cells/mm3 on cART prior to admission, hospitalized for 24 hours or more at either of two large, academic medical centers (where they also attended follow-up clinic visits) for a non-HIV-related illness, and that survived to hospital discharge between January 1st 2010 and December 31st 2015 were eligible for analysis. The primary outcome was the presence of an HIV RNA measurement as recommended by national guidelines within 6 months of hospital discharge. Secondary outcomes included the incidence of transient viremia and loss of VS after discharge.

Results

A total of 329 patients were included. The median age was 51 years (interquartile range [IQR] 44-58), 76.6% were male, and 48.3% were African American. The median CD4 count was 484 cells/mm3 (IQR 357-629) and 85.4% (n=281) had an undetectable HIV RNA prior to admission. Among the 97.6% (n=321) of patients with an HIV RNA measurement after hospital discharge, the median time to HIV RNA measurement was 2.4 months (IQR=1.2-4.1) and 86.3% (n=284) had an HIV RNA measurement within 6 months. Among patients who were undetectable prior to admission, transient viremia after discharge occurred in 7.1% (n=20) within a median of 2.5 months (IQR 1.3-4.1) and 4 of these patients lost VS. Three of the four patients with loss of VS were admitted for a non-HIV-related infection and all were on protease inhibitor-based regimens.

Conclusion

HIV RNA monitoring appears to occur according to guideline recommendations in the majority of PLWH after hospitalization for a non-HIV-related illness. Despite the occurrence of transient viremia, loss of VS was rare. Future studies should focus on risk factors for loss of VS.

Disclosures

Milena M. Murray, PharmD, MSc, BCIDP, AAHIVP, Merck (Speaker’s Bureau)

Seeking international consensus on approaches to primary tumour treatment in Ewing sarcoma

BACKGROUND

The local treatment of Ewing sarcoma of bone involves surgery, radiotherapy or both. The selection of treatment depends on the anatomical extent of the tumour, the effectiveness of the proposed treatment, its morbidity, and the expectation of cure. However, not only are there variations in the approach to local treatment between individual patients, but also between treatment centres and countries. Our aim was to explore variation in practice and develop consensus statements about local treatment.

METHODS

A three stage modified Delphi technique was used with international collaborators. This involved an expert panel to identify areas of controversy, an online survey of international collaborators and a consensus meeting in London, UK in June 2017. In the consensus meeting, teams of clinicians discussed the local management of selected cases and their responses were collected with electronic voting.

RESULTS

Areas of greater or less consensus were identified. The lack of evidence underpinning different approaches was noted and areas for collaborative research became apparent.

CONCLUSION

This has demonstrated that there is an international consensus around many aspects of the local treatment of Ewing sarcoma of bone, including the use of specialist MultiDisciplinary Team (MDT) meetings with access to all appropriate treatments. However, considerable variation remains including the use of different staging investigations, decision making, definitions of response, and radiotherapy doses and timing. Further collaborative work should be undertaken to determine the impact of these variations in order to define best practice.

Ulnar Nerve Entrapment at Elbow in an Adult Patient with Macrodactyly

We describe a case of an adult patient presenting with cubital tunnel syndrome in the setting of previously undiagnosed macrodactyly. Early diagnosis and management of macrodactyly is important to help prevent symptoms associated with compromised peripheral nerves and reduce the likelihood of the permanent motor and sensory sequelae of prolonged nerve compression.

224. Cost Analysis of a Significant Decrease in Vancomycin Use as a Result of an Antimicrobial Stewardship Intervention

Background

A previous pre–post quasi-experimental study performed at an academic medical center assessed benefits of daily stewardship review with and without rapid diagnostic technology (RDT). The study found no difference in time to effective antibiotic therapy when comparing daily stewardship review to RDT and historical control groups. However, vancomycin duration of therapy significantly decreased with daily stewardship review compared with control (31.8 vs. 66 hours, P < 0.001). Subsequent elimination of this RDT saved the institution $53,000 in annual costs. However, the effect of the decrease in vancomycin use on this institution’s annual costs is unknown.

Methods

The purpose of the present study is to determine the difference in institutional costs associated with vancomycin after implementation of a stewardship intervention. A retrospective cost analysis was performed which included hospitalized adults on vancomcyin for positive blood cultures from June to October 2014 (preintervention) and June to October 2015 (postintervention). The primary outcome was the amount of institutional cost saved, including drug, phlebotomy, laboratory, nursing, and pharmacy costs. Secondary outcomes included vancomycin DOT/1,000 patient-days, nephrotoxicity, in-hospital mortality, and length of stay.

Results

Institutional cost savings associated with vancomycin over 5 months amounted to $2,900 for an extrapolated cost savings of $6,960 per year. Although this cost savings was minimal, there were decreases in each individual vancomycin cost component. Drug acquisition was associated with the largest cost reduction represented by a 26% decline. Next, phlebotomy and laboratory costs each decreased by 24%, while nursing and pharmacy costs decreased by 7% and 4%, respectively. There were no differences in vancomycin DOT/1,000 patient-days, nephrotoxicity, in-hospital mortality, or length of stay.

Conclusion

Vancomycin is associated with many hidden ancillary costs, and pharmacy and nursing labor remain substantial despite a reduction in its use. The tracking of antimicrobial stewardship actions is highly recommended; however, more research is needed to determine the optimal process for a vancomycin cost analysis.

Disclosures

All authors: No reported disclosures.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Cyclophosphamide-based in vivo T-cell depletion for HLA-haploidentical transplantation in Fanconi anemia

Allogeneic hematopoietic cell transplantation (HCT) is the only known cure for patients with Fanconi anemia (FA) who develop aplasia or leukemia. However, transplant regimens typically contain high-dose alkylators, which are poorly tolerated in FA patients. Furthermore, as many patients lack human leukocyte antigen (HLA)-matched family donors, alternative donors are used, which can increase the risk of both graft rejection and graft-versus-host disease (GVHD). To improve on these three concerns, we developed a multi-institutional clinical trial using a fludarabine (FLU)-based conditioning regimen with limited alkylators/low-dose radiation, HLA-haploidentical marrow, followed by reduced-dose cyclophosphamide (CY) to treat three FA patients with aplasia. All three patients engrafted with 100% donor CD3 chimerism at 1 month. One patient died early from disseminated toxoplasmosis infection. Of the two survivors, one had significant pretransplant co-morbidities and inadequate immunosuppression, and developed severe acute GVHD. The other patient had only mild acute and no chronic GVHD. With a follow-up of 2 and 3 years, respectively, both patients are doing well, are transfusion-independent, and maintain full donor chimerism. The patient with severe GVHD has resolving oral GVHD and good quality of life. We conclude that using low-intensity conditioning, HLA-haploidentical marrow, and reduced-dose CY for in vivo T-cell depletion can correct life-threatening aplasia in FA patients.

Analysis of hepatic glycogen-associated proteins

Glycogen particles are associated with a population of proteins that mediate its biological functions, including: management of glucose flux into and out of the glycogen particle, maintenance of glycogen structure and regulation of particle size, number, and cellular location. A survey of the glycogen-associated proteome would be predicted to identify the relative representation of known members of this population, and associations with unexpected proteins that have the potential to mediate other functions of the glycogen particle. We therefore purified glycogen particles from both mouse and rat liver, using different techniques, and analyzed the resulting tryptic peptides by MS. We also specifically eluted glycogen-binding proteins from the pellet using malto-oligosaccharides. Comparison of the rat and mouse populations, and analysis of specifically eluted proteins allow some conclusions to be made about the hepatic glycogen sub-proteome. With the exception of glycogen branching enzyme all glycogen metabolic proteins were detected. Novel associations were identified, including ferritin and starch-binding domain protein 1, a protein that contains both a transmembrane endoplasmic reticulum signal peptide and a carbohydrate-binding module. This study therefore provides insight into the organization of the glycogen proteome, identifies other associated proteins and provides a starting point to explore the dynamic nature and cellular distribution of this metabolically important protein population.