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The phase III clinical study of adjuvant liposomal muramyl tripeptide (MTP-PE) in resected high-grade osteosarcoma (OS) documented positive results that have been translated into regulatory approval, supporting initial promise for innate immune therapies in OS. There remains, however, no new approved treatment such as MTP-PE for either metastatic or recurrent OS. Whilst the addition of different agents, including liposomal MTP-PE, to surgery for metastatic or recurrent high-grade osteosarcoma has tried to improve response rates, a mechanistic hiatus exists in terms of a detailed understanding the therapeutic strategies required in advanced disease. Here we report a Bayesian designed multi-arm, multi-centre, open-label phase II study with randomisation in patients with metastatic and/or recurrent OS, designed to investigate how patients with OS might respond to liposomal MTP-PE, either given alone or in combination with ifosfamide. Despite the trial closing because of poor recruitment within the allocated funding period, with no objective responses in eight patients, we report the design and feasibility outcomes for patients registered into the trial. We demonstrate the feasibility of the Bayesian design, European collaboration, tissue collection with genomic analysis and serum cytokine characterisation. Further mechanistic investigation of liposomal MTP-PE alone and in combination with other agents remains warranted in metastatic OS.
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Neoplasias Óseas , Osteosarcoma , Acetilmuramil-Alanil-Isoglutamina/análogos & derivados , Teorema de Bayes , Biomarcadores , Neoplasias Óseas/patología , Humanos , Liposomas , Recurrencia Local de Neoplasia/tratamiento farmacológico , Osteosarcoma/patología , FosfatidiletanolaminasRESUMEN
OBJECTIVE: Lung cancer patients from ethnic minorities have poorer outcomes than their Caucasian counterparts. We compared lung cancer intervals between culturally and linguistically diverse (CALD) and Anglo-Australian patients to identify ethnic disparities. METHODS: This was a prospective, observational cohort study comprising a patient survey and reviews of patients' hospital and general practice records. Across three states, 577 (407 Anglo-Australian and 170 CALD) patients were recruited and their hospital records reviewed. The survey was returned by 189 (135 Anglo-Australian and 54 CALD) patients, and a review was completed by general practitioners (GPs) of 99 (76 Anglo-Australian and 23 CALD) patients. Survival and Cox regression analyses were conducted. RESULTS: CALD patients had longer hospital diagnostic interval [median 30 days, 95% confidence interval (CI) 26-34] than Anglo-Australian patients (median 17, 95% CI 14-20), p = 0.005, hazard ratio (HR) = 1.32 (95% CI 1.09-1.60). This difference persisted after relevant factors were taken into consideration, adjusted HR = 1.26 (95% CI 1.03-1.54, p = 0.022). CALD patients also reported longer prehospital intervals; however, these differences were not statistically significant. CONCLUSION: Target interventions need to be developed to address ethnic disparity in hospital diagnostic interval.
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Etnicidad , Neoplasias Pulmonares , Australia , Humanos , Estudios Prospectivos , Población BlancaRESUMEN
PURPOSE: Improving the coordination of care for people with lung cancer is a health priority. This study aimed to tailor an existing care coordination survey for a lung cancer population, investigate coordination experiences for patients who had received hospital-based treatment and identify any factors that may be associated with poor care coordination. METHODS: We conducted a cross-sectional survey of lung patients within two tertiary hospitals in Sydney, Australia. The Cancer Care Coordination Questionnaire for Patients (CCCQ-P) is a psychometrically valid and reliable survey originally developed for colorectal cancer. We pilot tested a survey adaptation with lung cancer patients, support group members and medical specialists (n = 49). A revised survey was mailed to eligible patients via their medical specialist. RESULTS: Fifty-three of 118 eligible participants (45%) completed the CCCQ-P; most had early-stage disease and were about 70 years old. Overall, participants reported positive experiences of care coordination (mean total score 78.1), with high scores on communication and navigation subscales. The most problematic areas related to administrative aspects of care coordination and communication and information provision. Two patient groups (those residing in regional and rural areas, or no experience with the health system prior to diagnosis) reported significantly lower scores on the navigation subscale. CONCLUSIONS: This study found that lung cancer patients' experience of care coordination was positive, but highlighted the need for strategies to assist patients living in rural areas, and those with no experience of the health care system. The CCCQ-P survey instrument can be used in future lung cancer studies.
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Atención a la Salud/tendencias , Neoplasias Pulmonares/diagnóstico , Anciano , Comunicación , Estudios Transversales , Femenino , Humanos , Neoplasias Pulmonares/patología , Masculino , Encuestas y CuestionariosRESUMEN
BACKGROUND: Lung cancer is the leading cause of cancer mortality worldwide. Early diagnosis and treatment is a key factor in reducing mortality and improving patient outcomes. To achieve this, it is important to understand the diagnostic pathways of cancer patients. Patients from Culturally and Linguistically Diverse (CALD) are a vulnerable group for lung cancer with higher mortality rates than Caucasian patients. The aim of this study is to explore differences in the lung cancer diagnostic pathways between CALD and Anglo-Australian patients and factors underlying these differences. METHODS: This is a prospective, observational cohort study using a mixed-method approach. Quantitative data regarding time intervals in the lung cancer diagnostic pathways will be gathered via patient surveys, General practitioner (GP) review of general practice records, and case-note analysis of hospital records. Qualitative data will be gathered via structured interviews with lung cancer patients, GPs, and hospital specialists. The study will be conducted in five study sites across three states in Australia. Anglo-Australian patients and patients from five CALD groups (i.e., Arabic, Chinese, Greek, Italian and Vietnamese communities) will mainly be identified through the list of new cases presented at lung multidisciplinary team meetings. For the quantitative component, it is anticipated that 724 patients (362 Anglo-Australian and 362 CALD patients) will be recruited to obtain a final sample of 290 (145 per group) assuming a 50% patient survey completion rate and a 80% GP record review completion rate. For the qualitative component, 60 interviews with lung cancer patients (10 Anglo-Australian and 10 patients per CALD group), 20 interviews with GPs, and 20 interviews with specialists will be conducted. DISCUSSION: This is the first Australian study to compare the time intervals along the lung cancer diagnostic pathway between CALD and Anglo-Australian patients. The study will also explore the underlying patient, healthcare provider, and health system factors that influence the time intervals in the two groups. This information will improve our understanding of the effect of ethnicity on health outcomes among lung cancer patients and will inform future interventions aimed at early diagnosis and treatment for lung cancer, particularly patients from CALD backgrounds. TRIAL REGISTRATION: The project was retrospectively registered with Australian New Zealand Clinical Trials Registry (registration number: ACTRN12617000957392 , date registered: 4th July 2017).
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Diversidad Cultural , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/etnología , Australia , Protocolos Clínicos , Cultura , Médicos Generales , Humanos , Neoplasias Pulmonares/terapia , Estudios Prospectivos , Factores de TiempoRESUMEN
BACKGROUND: Melanotic neuroectodermal tumor of infancy (MNTI) is exceptionally rare and occurs predominantly in the head and neck (92.8 % cases). The patient reported here is only the eighth case of MNTI presenting in an extremity, and the first reported in the fibula. CASE PRESENTATION: A 2-month-old female presented with a mass arising in the fibula. Exhaustive genomic, transcriptomic, epigenetic and pathological characterization was performed on the excised primary tumor and a derived cell line. Whole-exome analysis of genomic DNA from both the tumor and blood indicated no somatic, non-synonymous coding mutations within the tumor, but a heterozygous, unique germline, loss of function mutation in CDKN2A (p16(INK4A), D74A). SNP-array CGH on DNA samples revealed the tumor to be euploid, with no detectable gene copy number variants. Multiple chromosomal translocations were identified by RNA-Seq, and fusion genes included RPLP1-C19MC, potentially deregulating the C19MC cluster, an imprinted locus containing microRNA genes reactivated by gene fusion in embryonal tumors with multilayered rosettes. Since the presumed cell of origin of MNTI is from the neural crest, we also compared gene expression with a dataset from human neural crest cells and identified 185 genes with significantly different expression. Consistent with the melanotic phenotype of the tumor, elevated expression of tyrosinase was observed. Other highly expressed genes encoded muscle proteins and modulators of the extracellular matrix. A derived MNTI cell line was sensitive to inhibitors of lysine demethylase, but not to compounds targeting other epigenetic regulators. CONCLUSIONS: In the absence of somatic copy number variations or mutations, the fully transformed phenotype of the MNTI may have arisen in infancy because of the combined effects of a germline CDKN2A mutation, tumor promoting somatic fusion genes and epigenetic deregulation. Very little is known about the etiology of MNTI and this report advances knowledge of these rare tumors by providing the first comprehensive genomic, transcriptomic and epigenetic characterization of a case.
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Neoplasias Óseas/genética , Inhibidor p18 de las Quinasas Dependientes de la Ciclina/genética , Peroné/patología , Mutación de Línea Germinal , Tumor Neuroectodérmico Melanótico/genética , Proteínas de Fusión Oncogénica/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Lactante , Fosfoproteínas/genética , Proteínas Ribosómicas/genética , Análisis de Secuencia de ADN , Análisis de Secuencia de ARNRESUMEN
Chronic myeloid leukaemia (CML) can be considered as a paradigm for neoplasias that evolve through a multi-step process. CML is also one of the best examples of a disease that can be targeted by molecular therapy; however, the success of new 'designer drugs' is largely restricted to the chronic phase of the disease. If not cured at this stage, CML invariably progresses and transforms into an acute-type leukaemia undergoing a 'blast crisis'. The causes of this transformation are still poorly understood. What mechanisms underlie this progression, and are they shared by other common cancers?
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Crisis Blástica , Progresión de la Enfermedad , Leucemia Mielógena Crónica BCR-ABL Positiva/patología , Modelos Biológicos , Animales , Diferenciación Celular , Proteínas de Fusión bcr-abl/fisiología , Perfilación de la Expresión Génica , Genes Supresores de Tumor/fisiología , Inestabilidad Genómica , Humanos , Leucemia Mielógena Crónica BCR-ABL Positiva/genética , Neoplasias/patologíaRESUMEN
There is an increasing trend for the use of multi-disciplinary teams (MDT) in the management of complex medical conditions. The latter may include various cancers, including lung cancer. However, the use of MDT is not restricted to cancer management, but may include complex conditions like diabetes and other non-malignant disorders. There is an increasing trend to use MDT in the investigation and management of patients with suspected or proven lung cancer. This review examines the evidence that supports the efficacy, or otherwise, of lung cancer management in a MDT as opposed to individual care, who should be a member of a lung cancer MDT, and the specific role of the respiratory physician in a lung cancer MDT. Although it may seem to make common sense to manage lung cancer in a MDT setting, there is actually little in the way of high quality data to support this concept. The logistic and ethical difficulties in researching this issue are highlighted in this review.
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Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/terapia , Grupo de Atención al Paciente , Neumología , HumanosRESUMEN
Protein synthesis translates information from messenger RNAs into functional proteomes. Because of the finite nature of the resources required by the translational machinery, both the overall protein synthesis activity of a cell and activity on individual mRNAs are controlled by the allocation of limiting resources. Upon introduction of heterologous sequences into an organism-for example for the purposes of bioprocessing or synthetic biology-limiting resources may also become overstretched, thus negatively affecting both endogenous and heterologous gene expression. In this study, we present a mean-field model of translation in Saccharomyces cerevisiae for the investigation of two particular translational resources, namely ribosomes and aminoacylated tRNAs. We firstly use comparisons of experiments with heterologous sequences and simulations of the same conditions to calibrate our model, and then analyse the behaviour of the translational system in yeast upon introduction of different types of heterologous sequences. Our main findings are that: competition for ribosomes, rather than tRNAs, limits global translation in this organism; that tRNA aminoacylation levels exert, at most, weak control over translational activity; and that decoding speeds and codon adaptation exert strong control over local (mRNA specific) translation rates.
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Regulación Fúngica de la Expresión Génica , Biosíntesis de Proteínas , Aminoacil-ARN de Transferencia/metabolismo , Ribosomas/metabolismo , Saccharomyces cerevisiae/genética , Modelos Genéticos , ARN Mensajero/metabolismo , ARN de Transferencia/metabolismo , Saccharomyces cerevisiae/metabolismoRESUMEN
BACKGROUND: The perceptions of using noninvasive ventilation (NIV) during exercise in patients with COPD who are naïve to NIV is unknown. The present study aimed to examine the perceptions of using NIV during exercise in people with COPD and to determine the relationship between patient perceptions with both baseline patient characteristics and exercise outcomes. METHODS: During a trial examining the effect of NIV during exercise on dynamic hyperinflation in people with COPD who were naïve to NIV, participants completed a 5-point Likert scale questionnaire (scored strongly disagree -2 to strongly agree +2) before and after using NIV during exercise and a semi-structured interview after using NIV during exercise. RESULTS: Eighteen participants, mean age (SD) 69 (7) y, FEV1/FVC 0.44 (0.08), FEV1 39 (7)% predicted, completed the study. Prior to exercise with NIV, participants were neutral about NIV, (mean [SD]) (0.67[0.84]). After exercise with NIV, participants felt that NIV made breathing easier (1.00 [0.77]) and that it helped exercise (1.06 [0.64]). There were moderate correlations between feeling that NIV was comfortable or effective and a change in exercise endurance time (ρ = - 0.588, P = .02), isotime inspiratory capacity (ρ = 0.488, P = .03), and measures of resting hyperinflation (ρ = 0.603, \P = .02). Interviews revealed that despite feeling comfortable using NIV during exercise, NIV might be too complicated for patients to manage outside a supervised environment. CONCLUSIONS: Individuals with COPD, naïve to NIV, and using NIV during exercise for the first time reported a positive effect of NIV on breathlessness and exercise performance. Participants' perceived benefit of NIV correlated moderately with increased endurance time and resting hyperinflation and with a reduction in dynamic hyperinflation during exercise, suggesting that patient reports could also aid selection of those who will benefit from NIV during exercise.
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Ventilación no Invasiva , Enfermedad Pulmonar Obstructiva Crónica , Anciano , Disnea , Tolerancia al Ejercicio , Humanos , Capacidad Inspiratoria , Persona de Mediana Edad , Enfermedad Pulmonar Obstructiva Crónica/terapiaRESUMEN
Over the last 10 years, with the development of culture-free bacterial identification techniques, understanding of how the microbiome influences diseases has increased exponentially and has highlighted potential opportunities for its use as a diagnostic biomarker and interventional target in many diseases including malignancy. Initial research focused on the faecal microbiome since it contains the densest bacterial populations and many other mucosal sites, such as the lungs, were until recently thought to be sterile. However, in recent years, it has become clear that the lower airways are home to a dynamic bacterial population sustained by the migration and elimination of microbes from the gastrointestinal and upper airway tracts. As in the gut, the lung microbiome plays an important role in regulating mucosal immunity and maintaining the balance between immune tolerance and inflammation. Studies to date have all shown that the lung microbiome undergoes significant changes in the setting of pulmonary disease. In lung cancer, animal models and small patient cohort studies have suggested that microbiome dysbiosis may not only impact tumour progression and response to therapy, particularly immunotherapy, but also plays a key role in cancer pathogenesis by influencing early carcinogenic pathways. These early results have led to concerted efforts to identify microbiome signatures that represent diagnostic biomarkers of early-stage disease and to consider modulation of the lung microbiome as a potential therapeutic strategy. Lung microbiome research is in its infancy and studies to date have been small, single centre with significant methodological variation. Large, multicentre longitudinal studies are needed to establish the clinical potential of this exciting field.
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BACKGROUND: With improvement in clinical care and longer survival of patients with cystic fibrosis (CF), pregnancy has become commonplace. However, the impact of pregnancy on maternal health and fetal outcomes requires ongoing review. METHODS: A retrospective study of 20 pregnancies from 18 women with CF during the period 1995-2009 was performed. Changes in lung function, body mass index (BMI) and development of gestational diabetes were recorded. Fetal outcomes and maternal survival were examined, and the influence of pre-pregnancy parameters on outcomes was evaluated. RESULTS: Mean maternal age at pregnancy was 29±5 years with a mean pre-pregnancy forced expiratory volume in 1 s (FEV1) of 65.6±20.8% predicted. Eleven of 20 pregnancies had a pre-pregnancy FEV1 <60% predicted. During pregnancy, FEV1% predicted fell by 4.8% (CI 1.6-7.9), but recovered to baseline within 6 months post-partum. Mothers gained a mean weight of 7.6±3.2 kg, and gestational diabetes developed in 43% of women. All women delivered live births apart from one therapeutic abortion. Five infants were preterm, and two mature infants had low birth weight. Three mothers either died or required lung transplantation after pregnancy (range 2.5-8.0 years). FEV1 <60% predicted and BMI <20 kg/m(2) were significant predictors of fetal complications. CONCLUSION: Most women tolerated pregnancy well without major complications despite many having at least moderate lung function impairment. Pre-pregnancy FEV1 and BMI were important predictors of outcomes.
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Fibrosis Quística/epidemiología , Complicaciones del Embarazo/epidemiología , Resultado del Embarazo/epidemiología , Índice de Masa Corporal , Fibrosis Quística/complicaciones , Diabetes Gestacional/epidemiología , Femenino , Volumen Espiratorio Forzado , Humanos , Recién Nacido de Bajo Peso , Recién Nacido , Pulmón/fisiología , Trasplante de Pulmón/estadística & datos numéricos , Mortalidad Materna , Embarazo , Nacimiento Prematuro/epidemiología , Estudios RetrospectivosRESUMEN
BACKGROUND: During exercise, dynamic hyperinflation (DH), measured by a reduction in inspiratory capacity (IC), increases exertional dyspnea and reduces functional capacity in many patients with severe COPD. Although noninvasive ventilation (NIV) during exercise can improve exercise duration, the effect on DH is unclear. RESEARCH QUESTIONS: In people with COPD, resting hyperinflation, and evidence of DH during exercise, does bilevel NIV during exercise reduce DH and increase endurance time compared with exercise with no NIV, and does NIV with an individually titrated expiratory positive airway pressure (T-EPAP) reduce DH and increase exercise endurance time more than NIV with standardized EPAP (S-EPAP) of 5 cm H2O? STUDY DESIGN AND METHODS: A randomized crossover trial in which investigators and participants were blinded between NIV interventions was performed. Participants (N = 19; FEV1 of 1.02 ± 0.24 L (39% ± 6% predicted) completed three constant work rate endurance cycle tests in random order-no NIV, NIV with S-EPAP, and NIV with T-EPAP-during exercise. Primary outcomes were isotime IC and exercise endurance time. Outcome measures from each intervention were compared at isotime and at end exercise by using a linear mixed-model analysis. RESULTS: Compared with no NIV, isotime IC and endurance time were greater with both NIV with S-EPAP (mean difference: 95% CI, 0.19 L [0.10-0.28]; 95% CI, 153 s [24-280], respectively) and T-EPAP (95% CI, 0.22 L [0.13-0.32]; 95% CI, 145 s [28-259], respectively). There was no difference between NIV with S-EPAP and NIV with T-EPAP. INTERPRETATION: In people with COPD and DH during exercise, NIV during exercise reduced DH and increased cycle endurance time. An S-EPAP of 5 cm H2O was adequate to obtain these benefits. TRIAL REGISTRY: Australian New Zealand Clinical Trials Registry; No.: ACTRN12613000804785; URL: http://www.anzctr.org.au.
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Disnea/prevención & control , Disnea/fisiopatología , Tolerancia al Ejercicio/fisiología , Ventilación no Invasiva/métodos , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Enfermedad Pulmonar Obstructiva Crónica/rehabilitación , Anciano , Estudios Cruzados , Femenino , Humanos , Capacidad Inspiratoria/fisiología , Masculino , Índice de Severidad de la EnfermedadRESUMEN
Type 1 fimbriae are a known virulence factor in a number of pathogenic enterobacteriaceae, including Salmonella, Shigella and E. coli. Yet, they are also expressed by some commensal strains, notably of E. coli. One hypothesis of the role of fimbriae in commensals is that they evoke a small but tolerable host immune response in order to have the host release sialic acid, which is a valuable nutrient. Genetic evidence suggests that sialic acid down-regulates fimbriation. This has been believed to enable the cells to reduce virulence when the host response is increasing, thus avoiding a full activation of host defenses. In this article we assess the plausibility of this hypothesis using mathematical models. Our models lead us to two main conclusions: A slight activation of host defenses is only possible with a carefully tuned set of parameters, whereas under a wide range of parameters and assumptions, the model predicts the host defenses to be activated to at least half their potential in response to fimbriation. Secondly, the fact that fimbriation is suppressed by sialic acid seems irrelevant for the global qualitative properties.
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Fimbrias Bacterianas/fisiología , Interacciones Huésped-Parásitos/inmunología , Modelos Teóricos , Regulación hacia Abajo/efectos de los fármacos , Inmunidad , Modelos Biológicos , Ácido N-Acetilneuramínico/metabolismo , Ácido N-Acetilneuramínico/farmacología , VirulenciaRESUMEN
Multidisciplinary care (MDC) is considered best practice in lung cancer care. Health care services have made significant investments in MDC through the establishment of multidisciplinary team (MDT) meetings. This investment is likely to be sustained in future. It is imperative that MDT meetings are efficient, effective, and sufficiently nimble to introduce new innovations to enable best practice. In this article, we consider the 'evidence-practice gaps' in the implementation of lung cancer MDC. These gaps were derived from the recurrent limitations outlined in existing studies and reviews. We address the contributions that implementation science and quality improvement can make to bridge these gaps by increasing translation and improving the uptake of innovations by teams.
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This study examined the effects of hypoxia (80% arterial oxyhaemoglobin saturation for 20 min) and the accompanying changes in heart rate and blood pressure on two components of arterial stiffness in healthy men. Augmentation index (AIx) and time to reflection (Tr) representing measures of muscular artery and aortic stiffness, respectively, were continuously measured. At first, subjects were exposed to either hypoxia (n = 12) or room air (n = 5). During early hypoxia AIx increased by 6% before decreasing to baseline. After hypoxia AIx decreased by a further 6%. In contrast there was no change in Tr. Six subjects were then exposed to hypoxia following infusion with the nitric oxide (NO) synthase inhibitor NG-mono-methyl-L: -arginine (L-NMMA) or saline. During hypoxia AIx decreased by 12% following saline but increased by 14% after L-NMMA and Tr did not change. These findings suggest that hypoxia may induce NO-mediated vasodilatation of small muscular arteries but not the aorta.
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Arterias/fisiopatología , Hipoxia/fisiopatología , Adulto , Presión Sanguínea/fisiología , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Óxido Nítrico/farmacología , Resistencia Vascular/fisiología , Vasodilatación/fisiologíaRESUMEN
The role of the respiratory physician in diagnosing lung cancer has increased in complexity over the last 20 years. Adenocarcinoma is now the prevailing histopathological sub-type of non-small cell lung cancer (NSCLC) resulting in more peripheral cancers. Conventional bronchoscopy is often not sufficient to obtain adequate tissue samples for diagnosis. Radiologically guided transthoracic biopsy is a sensitive alternative, but carries significant risks. These limitations have driven the development of complimentary bronchoscopic navigation techniques for peripheral tumour localisation and sampling. Furthermore, linear endobronchial ultrasound with transbronchial needle aspiration (EBUS-TBNA) is increasingly being chosen as the initial diagnostic procedure for those with central lesions and/or radiological evidence of node-positive disease. This technique can diagnose and stage patients in a single, minimally invasive procedure with a diagnostic yield equivalent to that of surgical mediastinoscopy. The success of molecular targeted therapies and immune checkpoint inhibitors in NSCLC has led to the increasing challenge of obtaining adequate specimens for accurate tumour subtyping through minimally invasive procedures. This review discusses the changing epidemiology and treatment landscape of lung cancer and explores the utility of current diagnostic options in obtaining a tissue diagnosis in this new era of precision medicine.
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Chronic myeloid leukemia (CML) starts with the acquisition of a BCR-ABL fusion gene in a single hematopoietic stem cell, but the time to progression is unpredictable. Although the tyrosine kinase inhibitor imatinib mesylate is highly effective in the treatment of CML, its continuous administration is associated with development of resistance, particularly in advanced phase or blast crisis. We investigate here whether a feature of disease progression (i.e., elevated expression of Bcr-Abl in CD34+ progenitor cells from CML patients in blast crisis) has any bearing on the kinetics of resistance to imatinib. By studying cell lines that exogenously express Bcr-Abl over the range found from chronic phase to blast crisis of CML, we show that cells expressing high amounts of Bcr-Abl, as in blast crisis, are much less sensitive to imatinib and, more significantly, take a substantially shorter time for yielding a mutant subclone resistant to the inhibitor than cells with low expression levels, as in chronic phase. Our data suggest that the differential levels of the Bcr-Abl oncoprotein expressed by CD34+ CML cells may reflect the extent and duration of their response to imatinib; the relatively high levels of oncoprotein in advanced-phase disease may underlie the observed rapid development of resistance.