RESUMO
Radioactive iodine is a highly effective treatment for thyroid cancer and has now been used in clinical practice for more than 80 years. In general, the treatment is well tolerated. However, it can be logistically quite complex for patients due to the need to reduce iodine intake and achieve high levels of thyroid-stimulating hormone prior to treatment. Radiation protection precautions must also be taken to protect others from unnecessary radiation exposure following treatment. It has been well documented by thyroid cancer patient support groups that there is significant variation in practice across the UK. It is clear that some patients are being asked to observe unnecessarily burdensome restrictions that make it more difficult for them to tolerate the treatment. At the instigation of these support groups, a multidisciplinary group was assembled to examine the evidence and generate guidance on best practice for the preparation of patients for this treatment and the management of subsequent radiation protection precautions, with a focus on personalising the advice given to individual patients. The guidance includes advice about managing particularly challenging situations, for example treating patients who require haemodialysis. We have also worked together to produce a patient information leaflet covering these issues. We hope that the guidance document and patient information leaflet will assist centres in improving our patients' experience of receiving radioactive iodine. The patient information sheet is available as Supplementary Material to this article.
Assuntos
Proteção Radiológica , Neoplasias da Glândula Tireoide , Humanos , Adulto , Neoplasias da Glândula Tireoide/radioterapia , Neoplasias da Glândula Tireoide/tratamento farmacológico , Radioisótopos do Iodo/efeitos adversos , Tireotropina , Reino UnidoRESUMO
With increasing understanding of the molecular alterations leading to thyroid cancers in recent years we have seen a rapid increase in the number of effective targeted systemic therapies available for patients with advanced thyroid cancer; firstly with the advent of the multi-kinase inhibitors and more recently with more specific RET, BRAF, MEK, ALK and NTRK inhibitors. Although these developments are very welcome, they have resulted in a paradigm shift in the management of advanced thyroid cancer to which thyroid oncologists have had to rapidly adapt, learning how to supervise treatment safely with novel agents, the management of novel toxicities, when and how to arrange molecular genetic testing of cancers and, perhaps most importantly, determining when the optimum time is to start these treatments in what can often be a relatively indolent, if progressive, disease. We hope that these guidelines will support clinicians in making these decisions with their patients, as well as signposting and providing useful supporting information both for patients and clinicians.
Assuntos
Neoplasias da Glândula Tireoide , Humanos , Neoplasias da Glândula Tireoide/tratamento farmacológicoRESUMO
AIMS: Anaplastic thyroid cancer (ATC) is a rare but aggressive form of thyroid cancer with a median survival of 4 months. Recent advances in molecular profiling have shown that up to half of ATCs harbour the BRAF-V600E mutation. The aim of this study was to provide real-world data and experience on the use of combination therapy dabrafenib and trametinib in patients with BRAF-V600E-mutated advanced ATC. MATERIALS AND METHODS: We retrospectively evaluated patients with confirmed BRAF-V600E-mutated ATC, defined as patients with locally advanced or metastatic ATC with no locoregional, radical treatment options. Outcomes measured were overall survival, progression-free survival, response rate, discontinuation rate, dose reduction rate and toxicity data. RESULTS: Seventeen patients were evaluated and the mean age was 68 years. Ten patients died by the time of censoring. The median duration of follow-up was 12 months (3-43 months). The estimated median overall survival was 6.9 months (95% confidence interval 2.46 months - upper confidence interval not reached) and the median progression-free survival was 4.7 months (95% confidence interval 1.4-7.8 months). Dose interruptions and/or reductions were common, but none of the patients had to permanently discontinue treatment because of toxicities. Severe toxicities (grades 3 and 4) were uncommon. CONCLUSIONS: This study supports the indication of dabrafenib and trametinib in BRAF-V600E-mutated ATC as an effective and well-tolerated treatment in an historically difficult to treat cancer.
Assuntos
Carcinoma Anaplásico da Tireoide , Neoplasias da Glândula Tireoide , Humanos , Idoso , Carcinoma Anaplásico da Tireoide/tratamento farmacológico , Carcinoma Anaplásico da Tireoide/genética , Carcinoma Anaplásico da Tireoide/patologia , Estudos Retrospectivos , Proteínas Proto-Oncogênicas B-raf/genética , Neoplasias da Glândula Tireoide/tratamento farmacológico , Neoplasias da Glândula Tireoide/genética , Reino Unido , Mutação , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversosRESUMO
Multicentre clinical trials involving a dosimetry component are becoming more prevalent in molecular radiotherapy and are essential to generate the evidence to support individualised approaches to treatment planning and to ensure that sufficient patients are recruited to achieve the statistical significance required. Quality assurance programmes should be considered to support the standardisation required to achieve meaningful results. Trials should be designed to ensure that dosimetry results from image acquisition systems across centres are comparable by incorporating steps to standardise the methodologies used for the quantification of images and dosimetry. Furthermore, it is essential to assess the expertise and resources available at each participating site prior to trial commencement. A quality assurance plan should be drawn up and training provided if necessary. Standardisation of quantification and dosimetry methodologies used in a trial are essential to ensure that results from different centres may be collated. In addition, appropriate uncertainty analysis should be carried out to correct for differences in methodologies between centres. Recommendations are provided to support dosimetry studies based on the experience of several previous and ongoing multicentre trials.
Assuntos
Radiometria , Humanos , Garantia da Qualidade dos Cuidados de Saúde , Radioterapia (Especialidade) , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por ComputadorRESUMO
BACKGROUND: Nab-paclitaxel plus gemcitabine (nabP+gemcitabine) offers modest survival gains for patients with metastatic pancreatic ductal adenocarcinoma (PDAC). Sequential scheduling of nabP+gemcitabine in a PDAC mouse model improved efficacy; this hypothesis was tested in a clinical trial. METHODS: Patients with previously untreated metastatic PDAC were randomised to receive nabP+gemcitabine administered either concomitantly on the same day, or sequentially, with gemcitabine administered 24 h after nabP. The primary outcome measure was progression-free survival (PFS). Secondary outcome measures were objective response rate (ORR), overall survival (OS), safety, quality of life (QoL) and predictive biomarkers. RESULTS: In total, 71 patients received sequential (SEQ) and 75 concomitant (CON) treatment. Six-month PFS was 46% with SEQ and 32% with CON scheduling. Median PFS (5.6 versus 4.0 months, hazard ratio [HR] 0.67, 95% confidence interval [95% CI] 0.47-0.95, p = 0.022) and ORR (52% versus 31%, p = 0.023) favoured the SEQ arm; median OS was 10.2 versus 8.2 months (HR 0.93, 95% CI 0.65-1.33, p = 0.70). CTCAE Grade ≥3 neutropaenia incidence doubled with SEQ therapy but was not detrimental to QoL. Strongly positive tumour epithelial cytidine deaminase (CDA) expression favoured benefit from SEQ therapy (PFS HR 0.31, 95% CI 0.13-0.70). CONCLUSIONS: SEQ delivery of nabP+gemcitabine improved PFS and ORR, with manageable toxicity, but did not significantly improve OS. CLINICAL TRIAL REGISTRATION: ISRCTN71070888; ClinialTrials.gov (NCT03529175).
Assuntos
Albuminas/administração & dosagem , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Carcinoma Ductal Pancreático/tratamento farmacológico , Desoxicitidina/análogos & derivados , Paclitaxel/administração & dosagem , Neoplasias Pancreáticas/tratamento farmacológico , Idoso , Idoso de 80 Anos ou mais , Carcinoma Ductal Pancreático/mortalidade , Desoxicitidina/administração & dosagem , Esquema de Medicação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Pancreáticas/mortalidade , Intervalo Livre de Progressão , Gencitabina , Neoplasias PancreáticasRESUMO
AIM: To assess the predictive value of the U classification and the significance of follow-up ultrasound in those managed conservatively. MATERIALS AND METHODS: A retrospective observational study was carried out among 1,465 patients who underwent thyroid ultrasound in 2016 at a teaching hospital in UK. Details regarding U classification of nodules, cytology, histology in patients who underwent surgery, and follow-up ultrasound in those managed conservatively were obtained. RESULTS: Thyroid surgery was performed in 129 patients of which malignancy was seen in 35 (27.1%). The proportion of patients with cancer in U1-U5 categories were 0%, 13.6%, 30.4%, 40%, and 100%, respectively (Fisher's exact test p=0.001). There was no significant difference in U stage, cytology, or histology between incidental and symptomatic nodules. Among patients who did not undergo surgery 5% of U1, 14.6% of U2, 75% of U3, and 71.4% of U4 underwent repeat ultrasound. Radiological progression in nodule size was seen in 4.2% of U1, 1.9% of U2, 0% of U3, and 40% of U4 nodules at median duration of 306, 439, 274, and 748 days, respectively. CONCLUSIONS: U classification is reliable in risk-stratifying thyroid nodules. Patients with benign nodules without high-risk features do not require follow-up. The interval between scans in patients with indeterminate nodules can be extended to a period of 6-12 months.
Assuntos
Neoplasias da Glândula Tireoide/diagnóstico por imagem , Neoplasias da Glândula Tireoide/patologia , Nódulo da Glândula Tireoide/diagnóstico por imagem , Nódulo da Glândula Tireoide/patologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Guias de Prática Clínica como Assunto , Estudos Retrospectivos , Medição de Risco , Neoplasias da Glândula Tireoide/cirurgia , Nódulo da Glândula Tireoide/cirurgia , Tireoidectomia , Reino UnidoRESUMO
AIMS: Radiotherapy clinical trials are integral to the development of new treatments to improve the outcomes of patients with cancer. A collaborative study by the National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group and the National Institute for Health Research was carried out to understand better if and why inefficiencies occur in the set-up of radiotherapy trials in the UK. MATERIALS AND METHODS: Two online surveys collected information on the time taken for UK radiotherapy trials to reach key milestones during set-up and the research support currently being provided to radiotherapy centres to enable efficient clinical trial set-up. Semi-structured interviews with project managers and chief investigators identified better ways of working to improve trial set-up in the future. RESULTS: The timelines for the set-up of 39 UK radiotherapy trials were captured in an online survey showing that the median time from grant approval to trial opening was 600 days (range 169-1172). There were 38 responses from radiotherapy centres to a survey asking about the current support provided for radiotherapy research. Most of these centres have more than one type of staff member dedicated to supporting radiotherapy research. The most frequent barrier to radiotherapy trial set-up identified was lack of physicists' time and lack of time for clinical oncologists to carry out research activities. Four main themes around trial set-up were identified from semi-structured interviews: the importance of communication and building relationships, the previous experience of the chief investigator and clinical trials units, a lack of resources and having the time and personnel required to produce trial documentation and to process trial approval requests. CONCLUSIONS: This unique, collaborative project has provided up to date information about the current landscape of trial set-up and research support in the UK and identified several avenues on which to focus future efforts in order to support the excellent radiotherapy trial work carried out across the UK.
Assuntos
Neoplasias/radioterapia , Humanos , Inquéritos e Questionários , Reino UnidoRESUMO
AIMS: Lenvatinib is an oral multi-kinase inhibitor approved for the treatment of adults with progressive, locally advanced or metastatic, differentiated thyroid carcinoma refractory to radioactive iodine. MATERIALS AND METHODS: A literature review was undertaken to inform the development of consensus-based guidance for the routine management of adverse events associated with lenvatinib. PubMed was searched on 24 October 2017; the search terms were 'lenvatinib' and 'thyroid cancer'. RESULTS: Hypertension, diarrhoea, weight loss, skin toxicities and cardiovascular adverse events were considered. For grade 1/2 diarrhoea, initial treatment should be loperamide with a 1-week treatment interruption if diarrhoea persists and dose reduction if diarrhoea recurs on reinitiation of lenvatinib. Blood pressure should be monitored daily in patients with pre-existing hypertension, otherwise from 1 week after the initiation of lenvatinib and weekly for the first 2 months. For patients with systolic blood pressure ≥135 mmHg to <160 mmHg or diastolic blood pressure ≥85 mmHg to <100 mmHg, lenvatinib should be continued but antihypertensive therapy initiated/intensified. For patients who remain hypertensive, a treatment break can be considered with lenvatinib reinitiated at a reduced dose once the patient's blood pressure has stabilised for at least 48 h. Weight loss of 10% of baseline body weight or the onset of anorexia should be managed with a 1-week treatment break; patients should maintain a healthy, active lifestyle. For patients with grade 2 proteinuria, lenvatinib may be continued, but an angiotensin II receptor blocker or angiotensin converting enzyme inhibitor should be commenced. For grade >3 proteinuria, lenvatinib should be interrupted until proteinuria returns to 1+. For chronic proteinuria, lenvatinib should be stopped. Skin toxicities should be managed with moisturisers or emollients and soap substitutes. CONCLUSIONS: Prophylaxis, regular monitoring and symptomatic management with appropriate short treatment breaks and, for persistent adverse events, dose reductions, are recommended to enable patients to remain on the optimal dose regimen.
Assuntos
Antineoplásicos/efeitos adversos , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/terapia , Compostos de Fenilureia/efeitos adversos , Quinolinas/efeitos adversos , Neoplasias da Glândula Tireoide/tratamento farmacológico , Consenso , Gerenciamento Clínico , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/etiologia , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/patologia , Prova Pericial , Humanos , Neoplasias da Glândula Tireoide/patologiaRESUMO
AIMS: To obtain an overview of the management and outcomes of children aged 18 years or younger diagnosed with differentiated thyroid carcinoma of follicular cell origin across the UK, by collecting and analysing data from the limited number of centres treating these patients. This multicentre data might provide a more realistic perspective than single-institution series. MATERIALS AND METHODS: Six centres submitted data extracted from historical records on patients aged 18 years or younger, diagnosed between 1964 and 2017. The univariate and multivariable Cox proportional hazard model was used to identify potential predictors of progression-free survival, using national data as a control. RESULTS: Data on 166 patients were available for analysis. Females (74%) were predominant, and the age ranged from 3 to 19 years at diagnosis, mean 14.1 years. Nodal metastases were present in 51%; 12% had distant metastases. After surgery, 95% received radioactive iodine (39% on more than one occasion) and 4% received external beam radiotherapy. With a median follow-up duration of 5 years, 69% are alive with no evidence of disease; 20% are alive with a raised thyroglobulin level as the only evidence of residual disease; 6% have residual structural disease detectable on imaging; 2% have died, from cerebral metastases. CONCLUSION: Despite most patients having advanced disease at presentation, outcomes are very good. A national prospective registry should allow systematic collection of good-quality data and may facilitate research to further improve outcomes.
Assuntos
Adenocarcinoma Folicular , Câncer Papilífero da Tireoide , Neoplasias da Glândula Tireoide , Adenocarcinoma Folicular/epidemiologia , Adenocarcinoma Folicular/patologia , Adenocarcinoma Folicular/terapia , Adolescente , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Modelos de Riscos Proporcionais , Câncer Papilífero da Tireoide/epidemiologia , Câncer Papilífero da Tireoide/patologia , Câncer Papilífero da Tireoide/terapia , Neoplasias da Glândula Tireoide/epidemiologia , Neoplasias da Glândula Tireoide/patologia , Neoplasias da Glândula Tireoide/terapia , Reino Unido/epidemiologiaRESUMO
The management of early stage differentiated thyroid cancer (DTC) with low risk of recurrence has been the subject of much interest and investigation in the recent years. Locally advanced DTC and patients with a high risk of recurrent disease however needs further investigation. This short review will look at what constitutes high risk thyroid cancer, the definition of radioiodine refractory disease, the current management and areas of debate within this clinical setting.
Assuntos
Radioisótopos do Iodo/uso terapêutico , Neoplasias da Glândula Tireoide/radioterapia , Humanos , Risco , Neoplasias da Glândula Tireoide/tratamento farmacológicoRESUMO
BACKGROUND: Lung cancer is the most common cancer and smoking is the principal cause. Due to poor survival rates, symptom palliation and promotion of health-related quality of life (HRQoL) are primary outcomes for lung cancer patients. Given the established relationship between smoking and lung cancer, patients who have smoked may feel stigmatised or guilty after diagnosis, and more pessimistic about their illness and likely outcomes. This may have adverse implications for HRQoL. OBJECTIVES: We explored HRQoL and support experiences among newly diagnosed patients with advanced lung cancer. DESIGN: Semistructured interviews were conducted with nine patients and analysed using interpretative phenomenological analysis. RESULTS: Patients described the physical, emotional and social impact of disease on HRQoL. Fear of compromising their immune system and adjusting to new relationship roles had a wide-ranging effect on patients' HRQoL. Patients acknowledged links between lung cancer and smoking but some continued to smoke. They were sensitive to the opinions of medical staff about smoking especially those who continued to smoke or recently quit. CONCLUSIONS: We conclude that staff should give clearer advice about the adverse implications of continued smoking. We discuss the potential value of diagnosis as a teachable moment for promoting smoking cessation among patients and family members.
Assuntos
Neoplasias Pulmonares/psicologia , Qualidade de Vida/psicologia , Fumar/efeitos adversos , Adaptação Psicológica , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Cuidados Paliativos , Pesquisa Qualitativa , Abandono do Hábito de Fumar/psicologiaRESUMO
PURPOSE: Sentinel node biopsy (SNB) may identify lymph node metastases in patients with papillary thyroid cancer (PTC), enabling selective application of central node dissection (CND). The aim of this study was to assess the feasibility of implementing SNB in patients undergoing thyroidectomy for a cytologically indeterminate/suspicious/malignant thyroid nodule and to determine the potential improvement in clinical outcomes and the costs associated with the SNB technique. METHODS: The treatment strategies and clinical and pathological outcomes of two retrospective cohorts of patients who underwent preoperative thyroid FNA over a 5-year period in two different centres were studied. The potential for implementing the SNB technique and the benefits and costs associated with implementation were estimated. RESULTS: In centre 1, in 819 adult patients who had thyroid fine-needle aspiration cytology, the final cytology was indeterminate, suspicious and diagnostic of malignancy in 113, 29 and 28 patients, respectively. One hundred eight patients were 'suitable' for SNB. Twenty-three of these patients had PTC, six of whom underwent CND. Of these six patients, node metastasis was absent in five--the cohort in whom prophylactic CND may have been avoided consequent to a negative 'sentinel node' biopsy. Morbidity attributable to CND may have been avoided in up to four patients over a 5-year period. Costs associated with implementation of SNB outweighed any potential savings. Analysis of 491 patients in centre 2 confirmed that the benefit of SNB in PTC was similarly limited; morbidity attributable to CND may have been avoided in up to seven patients over a 5-year period. CONCLUSIONS: Even under ideal conditions (assuming 100 % node identification rate and 0 % false negative rate), the potential short- to medium-term benefit of sentinel node biopsy in patients with thyroid cancer in centres implementing a policy of selective or routine prophylactic CND is low.
Assuntos
Carcinoma/patologia , Metástase Linfática/patologia , Biópsia de Linfonodo Sentinela , Neoplasias da Glândula Tireoide/patologia , Adulto , Carcinoma/economia , Carcinoma/cirurgia , Carcinoma Papilar , Estudos de Coortes , Análise Custo-Benefício/economia , Inglaterra , Estudos de Viabilidade , Custos de Cuidados de Saúde/estatística & dados numéricos , Humanos , Esvaziamento Cervical/economia , Estadiamento de Neoplasias , Valor Preditivo dos Testes , Prognóstico , Estudos Retrospectivos , Biópsia de Linfonodo Sentinela/economia , Medicina Estatal/economia , Câncer Papilífero da Tireoide , Neoplasias da Glândula Tireoide/economia , Neoplasias da Glândula Tireoide/cirurgia , Nódulo da Glândula Tireoide/economia , Nódulo da Glândula Tireoide/patologia , Nódulo da Glândula Tireoide/cirurgia , Tireoidectomia/economiaRESUMO
BACKGROUND: REAL3 (Randomised ECF for Advanced or Locally advanced oesophagogastric cancer 3) was a phase II/III trial designed to evaluate the addition of panitumumab (P) to epirubicin, oxaliplatin and capecitabine (EOC) in untreated advanced oesophagogastric adenocarcinoma, or undifferentiated carcinoma. MAGIC (MRC Adjuvant Gastric Infusional Chemotherapy) was a phase III study which demonstrated that peri-operative epirubicin, cisplatin and infused 5-fluorouracil (ECF) improved survival in early oesophagogastric adenocarcinoma. PATIENTS AND METHODS: Analysis of response rate (RR; the primary end-point of phase II) and biomarkers in the first 200 patients randomised to EOC or modified dose (m) EOC+P in REAL3 was pre-planned to determine if molecular selection for the on-going study was indicated. KRAS, BRAF and PIK3CA mutations and PTEN expression were assessed in pre-treatment biopsies and results correlated with response to mEOC+P. Association between these biomarkers and overall survival (OS) was assessed in MAGIC patients to determine any prognostic effect. RESULTS: RR was 52% to mEOC+P, 48% to EOC. Results from 175 assessable biopsies: mutations in KRAS (5.7%), BRAF (0%), PIK3CA (2.5%) and loss of PTEN expression (15.0%). None of the biomarkers evaluated predicted resistance to mEOC+P. In MAGIC, mutations in KRAS, BRAF and PIK3CA and loss of PTEN (phosphatase and tensin homolog) were found in 6.3%, 1.0%, 5.0% and 10.9%, respectively, and were not associated with survival. CONCLUSIONS: The RR of 52% in REAL3 with mEOC+P met pre-defined criteria to continue accrual to phase III. The frequency of the mutations was too low to exclude any prognostic or predictive effect.
Assuntos
Adenocarcinoma/genética , Neoplasias Esofágicas/genética , Mutação/genética , Neoplasias Gástricas/genética , Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/mortalidade , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Classe I de Fosfatidilinositol 3-Quinases , Neoplasias Esofágicas/tratamento farmacológico , Neoplasias Esofágicas/mortalidade , Marcadores Genéticos/genética , Humanos , PTEN Fosfo-Hidrolase/genética , Fosfatidilinositol 3-Quinases/genética , Prognóstico , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas p21(ras) , Neoplasias Gástricas/tratamento farmacológico , Neoplasias Gástricas/mortalidade , Análise de Sobrevida , Proteínas ras/genéticaRESUMO
For almost two decades the properties of 'dwarf' galaxies have challenged the cold dark matter (CDM) model of galaxy formation. Most observed dwarf galaxies consist of a rotating stellar disk embedded in a massive dark-matter halo with a near-constant-density core. Models based on the dominance of CDM, however, invariably form galaxies with dense spheroidal stellar bulges and steep central dark-matter profiles, because low-angular-momentum baryons and dark matter sink to the centres of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present-day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different dark-matter particle candidate. Here we report hydrodynamical simulations (in a framework assuming the presence of CDM and a cosmological constant) in which the inhomogeneous interstellar medium is resolved. Strong outflows from supernovae remove low-angular-momentum gas, which inhibits the formation of bulges and decreases the dark-matter density to less than half of what it would otherwise be within the central kiloparsec. The analogues of dwarf galaxies-bulgeless and with shallow central dark-matter profiles-arise naturally in these simulations.
RESUMO
Supermassive black holes (SMBHs) are a ubiquitous component of the nuclei of galaxies. It is normally assumed that after the merger of two massive galaxies, a SMBH binary will form, shrink because of stellar or gas dynamical processes, and ultimately coalesce by emitting a burst of gravitational waves. However, so far it has not been possible to show how two SMBHs bind during a galaxy merger with gas because of the difficulty of modeling a wide range of spatial scales. Here we report hydrodynamical simulations that track the formation of a SMBH binary down to scales of a few light years after the collision between two spiral galaxies. A massive, turbulent, nuclear gaseous disk arises as a result of the galaxy merger. The black holes form an eccentric binary in the disk in less than 1 million years as a result of the gravitational drag from the gas rather than from the stars.
RESUMO
The known galaxies most dominated by dark matter (Draco, Ursa Minor and Andromeda IX) are satellites of the Milky Way and the Andromeda galaxies. They are members of a class of faint galaxies, devoid of gas, known as dwarf spheroidals, and have by far the highest ratio of dark to luminous matter. None of the models proposed to unravel their origin can simultaneously explain their exceptional dark matter content and their proximity to a much larger galaxy. Here we report simulations showing that the progenitors of these galaxies were probably gas-dominated dwarf galaxies that became satellites of a larger galaxy earlier than the other dwarf spheroidals. We find that a combination of tidal shocks and ram pressure swept away the entire gas content of such progenitors about ten billion years ago because heating by the cosmic ultraviolet background kept the gas loosely bound: a tiny stellar component embedded in a relatively massive dark halo survived until today. All luminous galaxies should be surrounded by a few extremely dark-matter-dominated dwarf spheroidal satellites, and these should have the shortest orbital periods among dwarf spheroidals because they were accreted early.