Surgeon and medical oncologist peer network effects on the uptake of the 21-gene breast cancer recurrence score assay

BACKGROUND

Drivers behind the adoption of gene expression profiling in breast cancer oncology have been shown to include exposure to physician colleagues' use of a given genomic test. We examined adoption of the Oncotype DX 21-gene breast cancer recurrence score assay (ODX) in the United States after its incorporation into clinical guidelines. The influence of patient-sharing ties and co-location with prior adopters and the role of these potential exposures across medical specialties on peers' adoption of the test were examined.

METHODS

We conducted a retrospective cohort study of women with incident breast cancer using a 100% sample of fee-for-service Medicare enrollee claims over 2008-2011. Peer networks connecting medical oncologists and surgeons treating these patients were constructed using patient-sharing and geographic co-location. The impact of peer connections on the adoption of ODX by physicians and testing of patients was modeled with multivariable hierarchical regression.

RESULTS

Altogether, 156,229 women identified with incident breast cancer met criteria for cohort inclusion. A total of 7689 ODX prescribing physicians were identified. Co-location with medical oncologists who adopted the test in the early period (2008-2009) was associated with a 1.38-fold increase in the odds of a medical oncologist adopting ODX in 2010-2011 (95% CI = 1.04-1.83), as was co-location with early-adopting surgeons (odds ratio [OR] = 1.25, 95% CI = 1.00-1.58). Patients whose primary medical oncologist was linked to an early-adopting surgeon through co-location (OR = 1.17, 95% CI = 1.04-1.32) or both patient-sharing and co-location (OR = 1.17, 95% CI = 1.03-1.34) were more likely to receive ODX.

CONCLUSIONS

Exposure to surgeon early adopters through peer networks and co-location was predictive of ODX uptake by medical oncologists and testing of patients. Interventions focused on the role of surgeons in molecular testing may improve the implementation of best practices in breast cancer care.

PEGylation of Polyethylenimine Lowers Acute Toxicity while Retaining Anti-Biofilm and β-Lactam Potentiation Properties against Antibiotic-Resistant Pathogens

Bacterial biofilms, often impenetrable to antibiotic medications, are a leading cause of poor wound healing. The prognosis is worse for wounds with biofilms of antimicrobial-resistant (AMR) bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), and multi-drug resistant Pseudomonas aeruginosa (MDR-PA). Resistance hinders initial treatment of standard-of-care antibiotics. The persistence of MRSA, MRSE, and/or MDR-PA often allows acute infections to become chronic wound infections. The water-soluble hydrophilic properties of low-molecular-weight (600 Da) branched polyethylenimine (600 Da BPEI) enable easy drug delivery to directly attack AMR and biofilms in the wound environment as a topical agent for wound treatment. To mitigate toxicity issues, we have modified 600 Da BPEI with polyethylene glycol (PEG) in a straightforward one-step reaction. The PEG-BPEI molecules disable β-lactam resistance in MRSA, MRSE, and MDR-PA while also having the ability to dissolve established biofilms. PEG-BPEI accomplishes these tasks independently, resulting in a multifunction potentiation agent. We envision wound treatment with antibiotics given topically, orally, or intravenously in which external application of PEG-BPEIs disables biofilms and resistance mechanisms. In the absence of a robust pipeline of new drugs, existing drugs and regimens must be re-evaluated as combination(s) with potentiators. The PEGylation of 600 Da BPEI provides new opportunities to meet this goal with a single compound whose multifunction properties are retained while lowering acute toxicity.

Patient and physician factors associated with Oncotype DX and adjuvant chemotherapy utilization for breast cancer patients in New Hampshire, 2010-2016

BACKGROUND

Oncotype DX® (ODX) is used to assess risk of disease recurrence in hormone receptor positive, HER2-negative breast cancer and to guide decisions regarding adjuvant chemotherapy. Little is known about how physician factors impact treatment decisions. The purpose of this study was to examine patient and physician factors associated with ODX testing and adjuvant chemotherapy for breast cancer patients in New Hampshire.

METHODS

We examined New Hampshire State Cancer Registry data on 5630 female breast cancer patients diagnosed from 2010 to 2016. We performed unadjusted and adjusted hierarchical logistic regression to identify factors associated with a patient's receipt of ODX, being recommended and receiving chemotherapy, and refusing chemotherapy. We calculated intraclass correlation coefficients (ICCs) to examine the proportion of variance in clinical decisions explained by between-physician and between-hospital variation.

RESULTS

Over the study period, 1512 breast cancer patients received ODX. After adjustment for patient and tumor characteristics, we found that patients seen by a male medical oncologist were less likely to be recommended chemotherapy following ODX (OR = 0.50 (95% CI = 0.34-0.74), p < 0.01). Medical oncologists with more clinical experience (reference: less than 10 years) were more likely to recommend chemotherapy (20-29 years: OR = 4.05 (95% CI = 1.57-10.43), p < 0.01; > 29 years: OR = 4.48 (95% CI = 1.68-11.95), p < 0.01). A substantial amount of the variation in receiving chemotherapy was due to variation between physicians, particularly among low risk patients (ICC = 0.33).

CONCLUSIONS

In addition to patient clinicopathologic characteristics, physician gender and clinical experience were associated with chemotherapy treatment following ODX testing. The significant variation between physicians indicates the potential for interventions to reduce variation in care.

Abstract A12: Evaluating physician network-based measures of care coordination through the lens of the patient experience

There is significant promise in analyzing physician patient-sharing networks to construct indirect measures of care coordination by defining relationships between physicians based on shared patients. This approach has the potential to uncover how otherwise latent organizational aspects of health care systems impact patient outcomes. A key challenge to this approach is how the various measures used to describe these networks infer the complex realities of health care delivery. The extent of patient-sharing relationships within physician networks has been associated with care utilization, cost of care, and some measures of care quality. While this approach has been validated to signal true professional relationships between physicians from the physicians’ perspective, it is unknown whether these measures reflect patients’ perceptions of their own care coordination. The objective of this study is to evaluate the associations between network-based measures of care coordination and patient-reported experience measures. We linked three publicly available data sources released by Centers for Medicare and Medicaid Services (CMS) that include national data on physician patient sharing in 2015, physician participation in a group practice, and patient-reported quality performance for group practices based on responses to the Consumer Assessment of Healthcare Providers and Systems (CAHPS) Survey in 2016. The outcomes of interest were patient-reported experience measures reflecting “Between visit communication,” “Clinicians working together for your care,” and “Getting timely care, appointments, and information” (CAHPS). The predictor variables of interests were physician group practice density (the number of physician pairs who share patients adjusting for total number of physician pairs) and clustering (the extent to which sets of three physicians all share patients). There were 476 groups that had patient-reported measures available. Patients’ perception of “Clinicians working together for your care” was significantly positively associated with both physician group practice density (p=0.02) and clustering (p=0.006). Physician group practice clustering was also significantly positively associated with “Getting timely care, appointments, and information” (p=0.005). This work suggests that network-based measures of care coordination are associated with some patient-reported experience measures. Evaluating and intervening on patient-sharing networks may provide novel strategies for initiatives aimed at improving quality of care and the patient experience.

Citation Format: Erika L. Moen, Julie P. Bynum. Evaluating physician network-based measures of care coordination through the lens of the patient experience [abstract]. In: Proceedings of the AACR Special Conference on Modernizing Population Sciences in the Digital Age; 2019 Feb 19-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(9 Suppl):Abstract nr A12.

Expanding the Spectrum of Antibiotics Capable of Killing Multidrug-Resistant Staphylococcus aureus and Pseudomonas aeruginosa

Infections from antibiotic-resistant Staphylococcus aureus and Pseudomonas aeruginosa are a serious threat because reduced antibiotic efficacy complicates treatment decisions and prolongs the disease state in many patients. To expand the arsenal of treatments against antimicrobial-resistant (AMR) pathogens, 600-Da branched polyethylenimine (BPEI) can overcome antibiotic resistance mechanisms and potentiate β-lactam antibiotics against Gram-positive bacteria. BPEI binds cell-wall teichoic acids and disables resistance factors from penicillin binding proteins PBP2a and PBP4. This study describes a new mechanism of action for BPEI potentiation of antibiotics generally regarded as agents effective against Gram-positive pathogens but not Gram-negative bacteria. 600-Da BPEI is able to reduce the barriers to drug influx and facilitate the uptake of a non-β-lactam co-drug, erythromycin, which targets the intracellular machinery. Also, BPEI can suppress production of the cytokine interleukin IL-8 by human epithelial keratinocytes. This enables BPEI to function as a broad-spectrum antibiotic potentiator, and expands the opportunities to improve drug design, antibiotic development, and therapeutic approaches against pathogenic bacteria, especially for wound care.

Overcoming Multidrug Resistance and Biofilms of Pseudomonas aeruginosa with a Single Dual-Function Potentiator of β-Lactams

Clinicians prescribe hundreds of millions of β-lactam antibiotics to treat the majority of patients presenting with bacterial infections. Patient outcomes are positive unless resistant bacteria, such as Pseudomonas aeruginosa (P. aeruginosa), are present. P. aeruginosa has both intrinsic and acquired antibiotic resistance, making clinical management of infection a real challenge, particularly when these bacteria are sequestered in biofilms. These problems would be alleviated if, upon the initial presentation of bacterial infection symptoms, clinicians were able to administer an antibiotic that kills both susceptible and otherwise resistant bacteria and eradicates biofilms. As the most common class of antibiotics, β-lactams could be used in a new drug if the leading causes of β-lactam antibiotic resistance, permeation barriers from lipopolysaccharide, efflux pumps, and β-lactamase enzymes, were also defeated. Against P. aeruginosa and their biofilms, the potency of β-lactam antibiotics is restored with 600 Da branched polyethylenimine (600 Da BPEI). Checkerboard assays using microtiter plates demonstrate the potentiation of piperacillin, cefepime, Meropenem, and erythromycin antibiotics. Growth curves demonstrate that only a combination of 600 Da BPEI and piperacillin produces growth inhibition against antibiotic resistant P. aeruginosa. Scanning electron microscopy (SEM) was used to confirm that the combination treatment leads to abnormal P. aeruginosa morphology. Data collected with isothermal titration calorimetry and fluorescence spectroscopy demonstrate a mechanism of action in which potentiation at low concentrations of 600 Da BPEI reduces diffusion barriers from lipopolysaccharides without disrupting the outer membrane itself. Coupled with the ability to overcome a reduction in antibiotic activity created by biofilm exopolymers, targeting anionic sites on lipopolysaccharides and biofilm exopolysaccharides with the same compound provides new opportunities to counter the rise of multidrug-resistant infections.

Modeling peer effect modification by network strength: The diffusion of implantable cardioverter defibrillators in the US hospital network

We develop methodology that allows peer effects (also referred to as social influence and contagion) to be modified by the structural importance of the focal actor's position in the network. The methodology is first developed for a single peer effect and then extended to simultaneously model multiple peer-effects and their modifications by the structural importance of the focal actor. This work is motivated by the diffusion of implantable cardioverter defibrillators (ICDs) in patients with congestive heart failure across a cardiovascular disease patient-sharing network of United States hospitals. We apply the general methodology to estimate peer effects for the adoption of capability to implant ICDs, the number of ICD implants performed by hospitals that are capable, and the number of patients referred to other hospitals by noncapable hospitals. Applying our novel methodology to study ICD diffusion across hospitals, we find evidence that exposure to ICD-capable peer hospitals is strongly associated with the chance a hospital becomes ICD-capable and that the direction and magnitude of the association is extensively modified by the strength of that hospital's position in the network, even after controlling for effects of geography. Therefore, interhospital networks, rather than geography per se, may explain key patterns of regional variations in healthcare utilization.

Low-Molecular-Weight Branched Polyethylenimine Potentiates Ampicillin against MRSA Biofilms

Methicillin-resistant Staphylococcus aureus (MRSA) infections pose a serious threat worldwide. MRSA is the predominant species isolated from medical-device-related biofilm infections and chronic wounds. Its ability to form biofilms grants it resistance to almost all antibiotics on the market. Answering the call for alternative treatments, our lab has been investigating the efficacy of 600 Da branched polyethylenimine (BPEI) as a β-lactam potentiator against bacterial biofilms. Our previous study showed promise against methicillin-resistant Staphylococcus epidermidis biofilms. This study extends our previous findings to eradicate a more virulent pathogen: MRSA biofilms. Microtiter minimum biofilm eradication concentration models, crystal violet assays, and electron microscopy images show synergistic effects between BPEI and ampicillin as a two-step mechanism: step one is the removal of the extracellular polymeric substances (EPS) to expose individual bacteria targets, and step two involves electrostatic interaction of BPEI with anionic teichoic acid in the cell wall to potentiate the antibiotic.

Artificial microbiome heterogeneity spurs six practical action themes and examples to increase study power-driven reproducibility

With >70,000 yearly publications using mouse data, mouse models represent the best engrained research system to address numerous biological questions across all fields of science. Concerns of poor study and microbiome reproducibility also abound in the literature. Despite the well-known, negative-effects of data clustering on interpretation and study power, it is unclear why scientists often house >4 mice/cage during experiments, instead of ≤2. We hypothesized that this high animal-cage-density  practice abounds in published literature because more mice/cage could be perceived as a strategy to reduce housing costs. Among other sources of 'artificial' confounding, including cyclical oscillations of the 'dirty-cage/excrement microbiome', we ranked by priority the heterogeneity of modern husbandry practices/perceptions across three professional organizations that we surveyed in the USA. Data integration (scoping-reviews, professional-surveys, expert-opinion, and 'implementability-score-statistics') identified Six-Actionable Recommendation Themes (SART) as a framework to re-launch emerging protocols and intuitive statistical strategies to use/increase study power. 'Cost-vs-science' discordance was a major aspect explaining heterogeneity, and scientists' reluctance to change. With a 'housing-density cost-calculator-simulator' and fully-annotated statistical examples/code, this themed-framework streamlines the rapid analysis of cage-clustered-data and promotes the use of 'study-power-statistics' to self-monitor the success/reproducibility of basic and translational research. Examples are provided to help scientists document analysis for study power-based sample size estimations using preclinical mouse data to support translational clinical trials, as requested in NIH/similar grants or publications.

An Integrated Gaussian Graphical Model to evaluate the impact of exposures on metabolic networks

Examining the effects of exogenous exposures on complex metabolic processes poses the unique challenge of identifying interactions among a large number of metabolites. Recent progress in the quantification of the metabolome through mass spectrometry (MS) and nuclear magnetic resonance (NMR) has given rise to high-dimensional biomedical data of specific metabolites that can be leveraged to study their effects in humans. These metabolic interactions can be evaluated using probabilistic graphical models (PGMs), which define conditional dependence and independence between components within and between heterogeneous biomedical datasets. This method allows for the detection and recovery of valuable but latent information that cannot be easily detected by other currently existing methods. Here, we develop a PGM method, referred to as an "Integrated Gaussian Graphical Model (IGGM)", to incorporate exposure concentrations of seven trace elements-arsenic (As), lead (Pb), mercury (Hg), cadmium (Cd), zinc (Zn), selenium (Se) and copper (Cu-into metabolic networks. We first conducted a simulation study demonstrating that the integration of trace elements into metabolomics data can improve the accuracy of detecting latent interactions of metabolites impacted by exposure in the network. We tested parameters such as sample size and the number of neighboring metabolites of a chosen trace element for their impact on the accuracy of detecting metabolite interactions. We then applied this method to measurements of cord blood plasma metabolites and placental trace elements collected from newborns in the New Hampshire Birth Cohort Study (NHBCS). We found that our approach can identify latent interactions among metabolites that are related to trace element concentrations. Application to similarly structured data may contribute to our understanding of the complex interplay between exposure-related metabolic interactions that are important for human health.

BPEI-Induced Delocalization of PBP4 Potentiates β-Lactams against MRSA

With its high morbidity rate and increasing resistance to treatment, methicillin-resistant Staphylococcus aureus (MRSA) is a grave concern in the medical field. In methicillin-susceptible strains, β-lactam antibiotics disable the penicillin binding proteins (PBPs) that cross-link the bacterial cell wall. However, methicillin-resistant strains have PBP2a and PBP4, which continue enzymatic activity in the presence of β-lactam antibiotics. The activity of PBP2a and PBP4 is linked to the presence of wall teichoic acid (WTA); thus, WTA has emerged as a target for antibiotic drug discovery. In this work, we disable WTA in situ using its anionic phosphodiester backbone to attract cationic branched polyethylenimine (BPEI). Data show that BPEI removes β-lactam resistance in common MRSA strains and clinical isolates. Fluorescence microscopy was used to investigate this mechanism of action. The results indicate that BPEI prevents the localization of PBP4 to the cell division septum, thereby changing the cellular morphology and inhibiting cell division. Although PBP4 is not required for septum formation, proper cell division and morphology require WTA; BPEI prevents this essential function. The combination of BPEI and β-lactams is bactericidal and synergistic. Because BPEI allows us to study the role of WTA in the cell wall without genetic mutation or altered translocation of biomolecules and/or their precursors, this approach can help revise existing paradigms regarding the role of WTA in prokaryotic biochemistry at every growth stage.

Antibiofilm Synergy of β-Lactams and Branched Polyethylenimine against Methicillin-Resistant Staphylococcus epidermidis

Microbial biofilms are ubiquitous in nature, and they pose a serious threat to public health. Staphylococcus epidermidis is the most common clinical isolate from healthcare- and medical device-related biofilm infections. No antibiotic currently on the market can eradicate pathogenic biofilms, which contain complex defense mechanisms composed of slimelike extracellular polymeric substances. Understanding the need to develop alternative approaches, we examine 600 Da branched polyethylenimine (BPEI) against methicillin-resistant Staphylococcus epidermidis (MRSE) biofilms. Here, a microtiter biofilm model is used to test the synergistic effects between the two components of our combination treatment: BPEI and β-lactam antibiotics. Electron microscopy was used to confirm the growth of MRSE biofilms from the model. Minimum biofilm eradication concentration assays, crystal violet assays, and biofilm kill curves suggest that BPEI exhibits antibiofilm activity and can potentiate β-lactams to eradicate MRSE biofilms.

Physician network position and patient outcomes following implantable cardioverter defibrillator therapy

OBJECTIVE

To evaluate two novel measures of physician network centrality and their associations with implantable cardioverter defibrillator (ICD) procedure volume and health outcomes.

DATA SOURCES

Medicare claims and the National Cardiovascular Data Registry data from 2007 to 2011.

STUDY DESIGN

We constructed a national cardiovascular disease patient-sharing physician network and used network analysis to characterize physician network centrality with two measures: within-hospital degree centrality (number of connections within a hospital) and across-hospital degree centrality (number of connections across hospitals). The primary outcome was risk-adjusted 2-year case fatality. Hierarchical logistic regression estimated the effects of physician's within-hospital and across-hospital degree centrality on case fatality. We included 105 109 ICD therapy patients and 3474 ICD implanting physicians in our analyses.

PRINCIPAL FINDINGS

After controlling for other physician and hospital characteristics, we observed greater risk-adjusted case fatality among patients treated by physicians in the highest across-hospital degree tertile compared to lowest tertile (OR [95% CI] = 1.10 [1.04-1.16], P = 0.001) and lowest tertile volume physicians compared with highest volume (OR [95% CI] = 0.90 [0.84-0.95], P < 0.001). Physician's within-hospital degree tertile was inversely associated with case fatality but not statistically significant.

CONCLUSIONS

Degree centrality measures capture information independent of procedure volume and raise questions about the quality of physicians with networks that predict worse health outcomes.

Evaluating Breast Cancer Care Coordination at a Rural National Cancer Institute Comprehensive Cancer Center Using Network Analysis and Geospatial Methods

BACKGROUND

Variation in cancer care coordination may affect care quality and patient outcomes. We sought to characterize the impact of geographic access to and dispersion of cancer care providers on variation in care coordination.

METHODS

Using electronic health record data from 2,507 women diagnosed with breast cancer at a National Cancer Institute Comprehensive Cancer Center from April 2011 to September 2015, a breast cancer patient-sharing physician network was constructed. Patient "care networks" represent the subnetworks of physicians with whom the focal patient had a clinical encounter. Patient care networks were analyzed to generate two measures of care coordination, care density (ratio of observed vs. potential connections between physicians), and clustering (extent to which physicians form connected triangles).

RESULTS

The breast cancer physician network included 667 physicians. On average, the physicians shared patients with 12 other physicians. Patients saw an average of 8 physicians during active treatment. In multivariable models adjusting for patient sociodemographic and clinical characteristics, we observed that greater travel burden (>2 hours) and lower geographic dispersion were associated with higher care density (P < 0.05 and P < 0.001, respectively) but lower care network clustering (P < 0.05).

CONCLUSIONS

Variation in network-based measures of care coordination is partially explained by patient travel burden and geographic dispersion of care.

IMPACT

Improved understanding of factors driving variation in patient care networks may identify patients at risk of receiving poorly coordinated cancer care.

Cationic Branched Polyethylenimine (BPEI) Disables Antibiotic Resistance in Methicillin-Resistant Staphylococcus epidermidis (MRSE)

Staphylococcus epidermidis is one of the most prevalent prokaryotic species on human skin and mucosal membranes that constitute the commensal flora. S. epidermidis has become one of the most common causes of primary bacteremia. Infections are difficult to diagnose because the pathogen has natural niches on human skin and the ability to adhere to inanimate surfaces via biofilms. Alarmingly, S. epidermidis has acquired resistance to many antibiotics, which presents a danger to human health. Known as methicillin-resistant S. epidermidis (MRSE), most clinical isolates of MRSE in North America exhibit β-lactam resistance primarily due to the presence of mecA, a gene that bestows β-lactam antibiotic resistance in a manner similar to methicillin-resistant Staphylococcus aureus (MRSA). MecA encodes for expression of penicillin-binding protein 2a (PBP2a), which is absent in β-lactam susceptible strains of S. epidermidis. We can disable this resistance factor in MRSE with 600-Da branched polyethylenimine (BPEI). Cationic BPEI targets anionic wall teichoic acid (WTA), an essential cofactor for proper functioning of PBP2a. We found that BPEI synergizes the activity of β-lactam antibiotics against MRSE. Growth curves suggest that the combination of BPEI and oxacillin is bactericidal. Electron micrographs indicate abnormalities in the cellular septa and cell walls of treated samples. Therefore, first-line clinical treatments can be effective against MRSE when used in combination with BPEI.

Nuclear Excluded Autism-Associated Phosphatase and Tensin Homolog Mutations Dysregulate Neuronal Growth

BACKGROUND

Phosphatase and tensin homolog (PTEN) negatively regulates downstream protein kinase B signaling, resulting in decreased cellular growth and proliferation. PTEN is mutated in a subset of children with autism spectrum disorder (ASD); however, the mechanism by which specific point mutations alter PTEN function is largely unknown. Here, we assessed how ASD-associated single-nucleotide variations in PTEN (ASD-PTEN) affect function.

METHODS

We used viral-mediated molecular substitution of human PTEN into Pten knockout mouse neurons and assessed neuronal morphology to determine the functional impact of ASD-PTEN. We employed molecular cloning to examine how PTEN's stability, subcellular localization, and catalytic activity affect neuronal growth.

RESULTS

We identified a set of ASD-PTEN mutations displaying altered lipid phosphatase function and subcellular localization. We demonstrated that wild-type PTEN can rescue the neuronal hypertrophy, while PTEN H93R, F241S, D252G, W274L, N276S, and D326N failed to rescue this hypertrophy. A subset of these mutations lacked nuclear localization, prompting us to examine the role of nuclear PTEN in regulating neuronal growth. We found that nuclear PTEN alone is sufficient to regulate soma size. Furthermore, forced localization of the D252G and W274L mutations into the nucleus partially restores regulation of soma size.

CONCLUSIONS

ASD-PTEN mutations display decreased stability, catalytic activity, and/or altered subcellular localization. Mutations lacking nuclear localization uncover a novel mechanism whereby lipid phosphatase activity in the nucleus can regulate mammalian target of rapamycin signaling and neuronal growth.

Social and Structural Determinants of Smoking Status and Quit Attempts Among Adults Living in 12 US States, 2015

PURPOSE

This study examined the relationships among intermediary determinants, structural determinants, and adult smoking status and quit attempts.

DESIGN

Secondary data analysis of cross-sectional data.

SETTING

Data come from the 2015 Behavioral Risk Factor Surveillance System (BRFSS), Social Context module. A national, representative sample from 12 US states (Alabama, Arkansas, Delaware, District of Columbia, Georgia, Louisiana, Minnesota, Mississippi, Missouri, Rhode Island, Tennessee, and Utah).

PARTICIPANTS

A total of 64 053 noninstitutionalized US adults aged ≥18 years.

MEASURES

Smoking status and quit attempts were outcome variables. Individual-level structural determinants (age, sex, race/ethnicity, marital status, education, and employment status) and intermediary determinants (housing insecurity, food insecurity, health insurance, binge drinking, and general health mental health) from BRFSS.

ANALYSIS

Weighted multivariate, multinomial logistic regression.

RESULTS

Current smoking was greater among men, respondents aged between 35 to 64 and 55 to 64, adults who reported food insecurity, housing insecurity, frequent mental distress, binge drinking, and who were unemployed. Current smokers had higher odds of making quit attempts in the past 12 months if they were non-Hispanic Black, graduated college, and reported food and housing insecurity.

CONCLUSION

Multifaceted smoking cessation interventions that address food and housing needs also incorporate screening for potential comorbidities such as mental distress and/or hazardous alcohol use and may be needed to enhance smoking cessation rates among racially diverse adults.

Assessing Variation in Implantable Cardioverter Defibrillator Therapy Guideline Adherence With Physician and Hospital Patient-sharing Networks

BACKGROUND

Implantable cardioverter defibrillator (ICD) therapy is used for primary prevention of death among people with heart failure, and new evidence in 2005 on its effectiveness changed practice guidelines in the United States.

OBJECTIVES

The objective of this study is to examine how the connectedness of physicians and hospitals, measured using network analysis, relates to guideline-consistent ICD implantation.

RESEARCH DESIGN

We constructed physician and hospital networks for cardiovascular disease. Physicians were linked if they shared cardiovascular disease patients; these links were aggregated by hospital affiliation to construct a hospital network.

SUBJECTS

Medicare beneficiaries who underwent ICD therapy for primary prevention from 2007 to 2011.

MEASURES

The clinical outcome of interest was guideline-consistent ICD implantation, calculated using the National Cardiovascular Data Registry. The exposure variables of interest were the network measures of the ICD surgeon, the referring hospital, and the hospital where the ICD surgery occurred.

RESULTS

We focused on patients who were referred between hospitals for ICD implantation because they were more likely influenced by the hospital network (n=28,179). Patients were less likely to meet guidelines if their referring hospital had more connections to other hospitals (OR, 0.49; 95% confidence interval, 0.25-0.96) and more likely to meet guidelines if their ICD surgery hospital had more connections (OR, 1.61; 95% confidence interval, 0.98-2.64). The ICD surgeon's network measures were not associated with guideline-consistent implantation.

CONCLUSIONS

Associations between the hospital network measures and guideline adherence suggests new approaches to better disseminate clinical guidelines across health systems.

Penalized estimation of sparse concentration matrices based on prior knowledge with applications to placenta elemental data

Identifying patterns of association or dependency among high-dimensional biological datasets with sparse precision matrices remains a challenge. In this paper, we introduce a weighted sparse Gaussian graphical model that can incorporate prior knowledge to infer the structure of the network of trace element concentrations, including essential elements as well as toxic metals and metaloids measured in the human placentas. We present the weighted L1 penalized regularization procedure for estimating the sparse precision matrix in the setting of Gaussian graphical models. First, we use simulation models to demonstrate that the proposed method yields a better estimate of the precision matrix than the procedures that fail to account for the prior knowledge of the network structure. Then, we apply this method to estimate sparse element concentration matrices of placental biopsies from the New Hampshire Birth Cohort Study. The chemical architecture for elements is complex; thus, the method proposed herein was applied to infer the dependency structures of the elements using prior knowledge of their biological roles.

Targeting Wall Teichoic Acid in Situ with Branched Polyethylenimine Potentiates β-Lactam Efficacy against MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) is a medical concern. Here, we show that branched polyethylenimine (BPEI), a nontoxic, cationic polymer, restores MRSA's susceptibility to β-lactam antibiotics. Checkerboard assays with MRSA demonstrated synergy between BPEI and β-lactam antibiotics. A time-killing curve showed BPEI to be bactericidal in combination with oxacillin. BPEI did not potentiate efficacy with vancomycin, chloramphenicol, or linezolid. When exposed to BPEI, MRSA increased in size and had difficulty forming septa. BPEI electrostatically binds to wall teichoic acid (WTA), a cell wall anionic polymer of Gram-positive bacteria that is important for localization of certain cell wall proteins. Lack of potentiation in a WTA knockout mutant supports the WTA-based mechanism. These data suggest that BPEI may prevent proper localization of cell wall machinery by binding to WTA; leading to cell death when administered in combination with β-lactam antibiotics. Negligible in vitro toxicity suggests the combination could be a viable treatment option.

An analysis of patient-sharing physician networks and implantable cardioverter defibrillator therapy

The application of social network analysis to the organization of healthcare delivery is a relatively new area of research that may not be familiar to health services statisticians and other methodologists. We present a methodological introduction to social network analysis with a case study of physicians' adherence to clinical guidelines regarding use of implantable cardioverter defibrillators (ICDs) for the prevention of sudden cardiac death. We focus on two hospital referral regions (HRRs) in Indiana, Gary and South Bend, characterized by different rates of evidence-based ICD use (86% and 66%, respectively). Using Medicare Part B claims, we construct a network of physicians who care for cardiovascular disease patients based on patient-sharing relationships. Approaches for weighting physician dyads and aggregating physician dyads by hospital are discussed. Then, we obtain a set of weighted network statistics for the positions of hospitals in their referral region, global statistics for the physician network within each hospital, and of the network positions of individual physicians within hospitals, providing the mathematical specification and sociological intuition underlying each measure. We find that adjusting for network measures can reduce the observed differences between referral regions for evidence-based ICD therapy. This study supports previous reports on how variation in physician network structure relates to utilization of care, and motivates future work using physician network measures to examine variation in evidence-based medicine.

Analyzing Clustered Data: Why and How to Account for Multiple Observations Nested within a Study Participant?

A conventional study design among medical and biological experimentalists involves collecting multiple measurements from a study subject. For example, experiments utilizing mouse models in neuroscience often involve collecting multiple neuron measurements per mouse to increase the number of observations without requiring a large number of mice. This leads to a form of statistical dependence referred to as clustering. Inappropriate analyses of clustered data have resulted in several recent critiques of neuroscience research that suggest the bar for statistical analyses within the field is set too low. We compare naïve analytical approaches to marginal, fixed-effect, and mixed-effect models and provide guidelines for when each of these models is most appropriate based on study design. We demonstrate the influence of clustering on a between-mouse treatment effect, a within-mouse treatment effect, and an interaction effect between the two. Our analyses demonstrate that these statistical approaches can give substantially different results, primarily when the analyses include a between-mouse treatment effect. In a novel analysis from a neuroscience perspective, we also refine the mixed-effect approach through the inclusion of an aggregate mouse-level counterpart to a within-mouse (neuron level) treatment as an additional predictor by adapting an advanced modeling technique that has been used in social science research and show that this yields more informative results. Based on these findings, we emphasize the importance of appropriate analyses of clustered data, and we aim for this work to serve as a resource for when one is deciding which approach will work best for a given study.

New themes in the biological functions of 5-methylcytosine and 5-hydroxymethylcytosine

5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) play a critical role in development and normal physiology. Alterations in 5-mC and 5-hmC patterns are common events in hematopoietic neoplasms. In this review, we begin by emphasizing the importance of 5-mC, 5-hmC, and their enzymatic modifiers in hematological malignancies. Then, we discuss the functions of 5-mC and 5-hmC at distinct genic contexts, including promoter regions, gene bodies, intron-exon boundaries, alternative promoters, and intragenic microRNAs. Recent advances in technology have allowed for the study of 5-mC and 5-hmC independently and specifically permitting distinction between the bases that show them to have transcriptional effects that vary by their location relative to gene structure. We extend these observations to their functions at enhancers and transcription factor binding sites. We discuss dietary influences on 5-mC and 5-hmC levels and summarize the literature on the effects of folate and vitamin C on 5-mC and 5-hmC, respectively. Finally, we discuss how these new themes in the functions of 5-mC and 5-hmC will likely influence the broader research field of epigenetics.

Characterization of CpG sites that escape methylation on the inactive human X-chromosome

In many whole genome studies of gene expression or modified cytosines, data from probes localized to the X-chromosome are removed from analyses due to gender bias. Previously, we observed population differences in cytosine modifications between Caucasian and African lymphoblastoid cell lines (LCLs) on the autosomes using whole genome arrays to measure modified cytosines. DNA methylation plays a critical role in establishment and maintenance of X-chromosome inactivation in females. Therefore, we reasoned that by investigating cytosine modification patterns specifically on the X-chromosome, we could obtain valuable information about a chromosome that is often disregarded in genome-wide analyses. We investigated population differences in cytosine modification patterns along the X-chromosome between Caucasian and African LCLs and identified novel sites that escape methylation on the inactive X-chromosome (Xi) in females. We characterized the chromatin state of these loci by incorporating the extensive histone modification ChIP-seq data generated by ENCODE. To explore the relationship between DNA and histone modifications further, we hypothesized that BRD4, a protein that binds acetylated histones, could be preventing some sites from becoming de novo methylated. To test this, we treated 4 female LCLs with JQ1, a small molecule inhibitor of BRD4, but found that JQ1 treatment induced minor changes in cytosine modification levels, and the majority of sites escaping methylation on the Xi remained unmethylated. This suggests that other epigenetic mechanisms or transcription factors are likely playing a larger role in protecting these sites from de novo methylation on the Xi.

Abstract 5461: The role of gene body cytosine modifications in MGMT expression and sensitivity to temozolomide

The goal of precision medicine is to use patient-specific markers to design individualized treatment strategies. Promoter methylation of O6-methylguanine-DNA methyltransferase (MGMT), which encodes for the DNA repair protein MGMT, has been shown to predict glioblastoma patient survival after treatment with temozolomide. Unfortunately, there is no approved therapeutic alternative for patients whose tumors have an unmethylated MGMT promoter and are unlikely to respond to temozolomide treatment. Promoter methylation status of MGMT is used to predict expression levels of MGMT, despite some observed discordance between promoter methylation and protein levels. We hypothesized that incorporation of MGMT gene body cytosine modification levels in models of temozolomide response may lead to better prediction of MGMT expression levels and, more importantly, improved methods of prediction for glioblastoma patient response to temozolomide. Using 91 human glioblastoma samples from The Cancer Genome Atlas, we observed significant variation in MGMT expression levels in patients with an unmethylated promoter, with higher levels of gene body cytosine modification correlating with higher gene expression levels. Furthermore, inducing hypomethylation across the MGMT gene body with decitabine resulted in decreased levels of MGMT gene expression in lymphoblastoid and glioblastoma cell lines. These data indicate an important functional role for gene body cytosine modifications in maintaining gene expression levels. We reasoned that the decrease in MGMT expression induced by decitabine might render resistant glioblastoma cell lines more sensitive to temozolomide. Indeed, MGMT-expressing glioblastoma cell lines pre-treated with decitabine became significantly more sensitive to temozolomide-induced cytotoxicity. Overall, our results demonstrate a functional role for gene body cytosine modification in regulating gene expression of MGMT and suggest that patients with an unmethylated MGMT promoter could benefit from pre-treatment with decitabine to increase tumor sensitivity to temozolomide.

Citation Format: Erika L. Moen, Amy L. Stark, Wei Zhang, M. Eileen Dolan, Lucy A. Godley. The role of gene body cytosine modifications in MGMT expression and sensitivity to temozolomide. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5461. doi:10.1158/1538-7445.AM2014-5461