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Search Results: 1 - 10 of 629 matches for " Virginie Rondeau "
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Investigating hospital heterogeneity with a multi-state frailty model: application to nosocomial pneumonia disease in intensive care units
Benoit Liquet, Jean Francois Timsit, Virginie Rondeau
BMC Medical Research Methodology , 2012, DOI: 10.1186/1471-2288-12-79
Abstract: We show how a simple multi-state frailty model can be used to study semi-competing risks while fully taking into account the clustering (in ICU) of the data and the longitudinal aspects of the data, including left truncation and right censoring. We suggest the use of independent frailty models or joint frailty models for the analysis of transition intensities. Two distinct models which differ in the definition of time t in the transition functions have been studied: semi-Markov models where the transitions depend on the waiting times and nonhomogenous Markov models where the transitions depend on the time since inclusion in the study. The parameters in the proposed multi-state model may conveniently be computed using a semi-parametric or parametric approach with an existing R package FrailtyPack for frailty models. The likelihood cross-validation criterion is proposed to guide the choice of a better fitting model.We illustrate the use of our approach though the analysis of nosocomial infections (ventilator-associated pneumonia infections: VAP) in ICU, with “alive discharge” and “death” in ICU as other endpoints. We show that the analysis of dependent survival data using a multi-state model without frailty terms may underestimate the variance of regression coefficients specific to each group, leading to incorrect inferences. Some factors are wrongly significantly associated based on the model without frailty terms. This result is confirmed by a short simulation study. We also present individual predictions of VAP underlining the usefulness of dynamic prognostic tools that can take into account the clustering of observations.The use of multistate frailty models allows the analysis of very complex data. Such models could help improve the estimation of the impact of proposed prognostic features on each transition in a multi-centre study. We suggest a method and software that give accurate estimates and enables inference for any parameter or predictive quantity of intere
frailtypack : An R Package for the Analysis of Correlated Survival Data with Frailty Models Using Penalized Likelihood Estimation or Parametrical Estimation
Virginie Rondeau,Yassin Mazroui,Juan R. Gonzalez
Journal of Statistical Software , 2012,
Abstract: Frailty models are very useful for analysing correlated survival data, when observations are clustered into groups or for recurrent events. The aim of this article is to present the new version of anR package called frailtypack. This package allows to t Cox models andfour types of frailty models (shared, nested, joint, additive) that could be useful for several issues within biomedical research. It is well adapted to the analysis of recurrent events such as cancer relapses and/or terminal events (death or lost to follow-up). The approach uses maximum penalized likelihood estimation. Right-censored or left-truncated data are considered. It also allows stratication and time-dependent covariates during analysis.
Separate and combined analysis of successive dependent outcomes after breast-conservation surgery: recurrence, metastases, second cancer and death
Virginie Rondeau, Simone Mathoulin-Pélissier, Lucie Tanneau, Annie J Sasco, Gaétan MacGrogan, Marc Debled
BMC Cancer , 2010, DOI: 10.1186/1471-2407-10-697
Abstract: Patients (n = 919) with a primary invasive breast cancer and treated in a cancer center in South-Western France with breast-conserving surgery from 1990 to 1994 and followed up to January 2006 were included. Several types of non-independent events could be observed for the same patient: a LRR, a contralateral breast cancer, DM, other primary cancer than breast and breast cancer death. Data were analyzed separately and together using a random-effects survival model.LRR represent the most frequent type of first failure (14.6%). The risk of any event is higher for young women (less than 40 years old) and in the first 10 years of follow-up after the surgery. In the combined analysis histological tumor size, grade, number of positive nodes, progesterone receptor status and treatment combination are prognostic factors of any event. The results show a significant dependence between these events with a successively increasing risk of a new event after the first and second event. The risk of developing a new failure is greatly increased (RR = 4.25; 95%CI: 2.51-7.21) after developing a LRR, but also after developing DM (RR = 3.94; 95%CI: 2.23-6.96) as compared to patients who did not develop a first event.We illustrated that the random effects survival model is a more satisfactory method to evaluate the natural history of a disease with multiple type of events.Several randomized trials have shown that breast-conserving surgery (BCS) plus locoregional radiotherapy is an appropriate method of primary therapy for the majority of stage I and II breast cancers and may be preferable to radical mastectomy because it provides survival equivalence while conserving the breast [1]. The main concern for both physicians and patients is therefore the risk of local or metastatic recurrence in the conserved breast or in the contralateral breast.The risk of recurrence (local, locoregional or contralateral), distant metastases (DM) or second primary cancer after breast cancer and their predict
Camus ou les promesses de la vie
Daniel Rondeau
Synergies Monde Mediterranéen , 2010,
Abstract:
Joint modelling of longitudinal and multi-state processes: application to clinical progressions in prostate cancer
Lo?c Ferrer,Virginie Rondeau,James J. Dignam,Tom Pickles,Hélène Jacqmin-Gadda,Cécile Proust-Lima
Statistics , 2015,
Abstract: Joint modelling of longitudinal and survival data is increasingly used in clinical trials on cancer. In prostate cancer for example, these models permit to account for the link between longitudinal measures of prostate-specific antigen (PSA) and the time of clinical recurrence when studying the risk of relapse. In practice, multiple types of relapse may occur successively. Distinguishing these transitions between health states would allow to evaluate, for example, how PSA trajectory and classical covariates impact the risk of dying after a distant recurrence post-radiotherapy, or to predict the risk of one specific type of clinical recurrence post-radiotherapy, from the PSA history. In this context, we present a joint model for a longitudinal process and a multi-state process which is divided into two sub-models: a linear mixed sub-model for longitudinal data, and a multi-state sub-model with proportional hazards for transition times, both linked by shared random effects. Parameters of this joint multi-state model are estimated within the maximum likelihood framework using an EM algorithm coupled to a quasi-Newton algorithm in case of slow convergence. It is implemented under R, by combining and extending the mstate and JM packages. The estimation program is validated by simulations and applied on pooled data from two cohorts of men with localized prostate cancer and treated by radiotherapy. Thanks to the classical covariates available at baseline and the PSA measurements collected repeatedly during the follow-up, we are able to assess the biomarker's trajectory, define the risks of transitions between health states, and quantify the impact of the PSA dynamics on each transition intensity.
Role of vandetanib in the management of medullary thyroid cancer
Brassard M, Rondeau G
Biologics: Targets and Therapy , 2012, DOI: http://dx.doi.org/10.2147/BTT.S24220
Abstract: le of vandetanib in the management of medullary thyroid cancer Review (3504) Total Article Views Authors: Brassard M, Rondeau G Published Date March 2012 Volume 2012:6 Pages 59 - 66 DOI: http://dx.doi.org/10.2147/BTT.S24220 Received: 11 February 2012 Accepted: 24 February 2012 Published: 08 March 2012 Maryse Brassard1*, Geneviève Rondeau2* 1Endocrinology Service, Department of Medicine, Centre Hospitalier Universitaire Affilié (CHA), Laval University, Quebec, Canada; 2Endocrinology Service, Department of Medicine, Centre Hospitalier de l'Université de Montréal (CHUM), University of Montreal, Montreal, Canada *Both authors contributed equally to this article Abstract: Traditionally available treatments, like cytotoxic chemotherapy and external-beam radiation therapy, are limited and essentially ineffective for metastatic medullary thyroid carcinoma (MTC). In the last decade, small-molecule tyrosine kinase inhibitors (TKI) have been introduced in the field of thyroid cancer, after having been shown effective in a wide variety of other tumors. This review focuses on vandetanib (ZD6474, ZactimaTM; AstraZeneca) and its role in the treatment of MTC. Vandetanib is an oral TKI that targets VEGF receptors 2 and 3, RET, and at higher concentrations, the epidermal growth factor (EGF) receptor. This drug has been tested in two important phase II studies which demonstrated that both the 100 and 300 mg/day dosage of vandetanib have antitumor activity on advanced MTC. A phase III trial (ZETA trial) evaluating vandetanib in 331 patients with locally advanced or metastatic MTC showed a significant prolongation of PFS for patients receiving vandetanib compared with placebo. Toxicity surveillance in all studies reported high rates of adverse effects with diarrhea, rash, fatigue and nausea being the most commonly experienced by patients. Vandetanib is currently approved in the United States for unresectable locally advanced or metastatic MTC and has become a new standard of care in this rare and indolent pathology.
Role of vandetanib in the management of medullary thyroid cancer
Brassard M,Rondeau G
Biologics: Targets and Therapy , 2012,
Abstract: Maryse Brassard1*, Geneviève Rondeau2* 1Endocrinology Service, Department of Medicine, Centre Hospitalier Universitaire Affilié (CHA), Laval University, Quebec, Canada; 2Endocrinology Service, Department of Medicine, Centre Hospitalier de l'Université de Montréal (CHUM), University of Montreal, Montreal, Canada*Both authors contributed equally to this articleAbstract: Traditionally available treatments, like cytotoxic chemotherapy and external-beam radiation therapy, are limited and essentially ineffective for metastatic medullary thyroid carcinoma (MTC). In the last decade, small-molecule tyrosine kinase inhibitors (TKI) have been introduced in the field of thyroid cancer, after having been shown effective in a wide variety of other tumors. This review focuses on vandetanib (ZD6474, ZactimaTM; AstraZeneca) and its role in the treatment of MTC. Vandetanib is an oral TKI that targets VEGF receptors 2 and 3, RET, and at higher concentrations, the epidermal growth factor (EGF) receptor. This drug has been tested in two important phase II studies which demonstrated that both the 100 and 300 mg/day dosage of vandetanib have antitumor activity on advanced MTC. A phase III trial (ZETA trial) evaluating vandetanib in 331 patients with locally advanced or metastatic MTC showed a significant prolongation of PFS for patients receiving vandetanib compared with placebo. Toxicity surveillance in all studies reported high rates of adverse effects with diarrhea, rash, fatigue and nausea being the most commonly experienced by patients. Vandetanib is currently approved in the United States for unresectable locally advanced or metastatic MTC and has become a new standard of care in this rare and indolent pathology.Keywords: vandetanib, medullary thyroid cancer, RET mutation, VEFGR
Robust Transmission of Speech LSFs Using Hidden Markov Model-Based Multiple Description Index Assignments
Paul Rondeau,Pradeepa Yahampath
EURASIP Journal on Audio, Speech, and Music Processing , 2008, DOI: 10.1155/2008/896021
Abstract: Speech coding techniques capable of generating encoded representations which are robust against channel losses play an important role in enabling reliable voice communication over packet networks and mobile wireless systems. In this paper, we investigate the use of multiple description index assignments (MDIAs) for loss-tolerant transmission of line spectral frequency (LSF) coefficients, typically generated by state-of-the-art speech coders. We propose a simulated annealing-based approach for optimizing MDIAs for Markov-model-based decoders which exploit inter- and intraframe correlations in LSF coefficients to reconstruct the quantized LSFs from coded bit streams corrupted by channel losses. Experimental results are presented which compare the performance of a number of novel LSF transmission schemes. These results clearly demonstrate that Markov-model-based decoders, when used in conjunction with optimized MDIA, can yield average spectral distortion much lower than that produced by methods such as interleaving/interpolation, commonly used to combat the packet losses.
Robust Transmission of Speech LSFs Using Hidden Markov Model-Based Multiple Description Index Assignments
Rondeau Paul,Yahampath Pradeepa
EURASIP Journal on Audio, Speech, and Music Processing , 2008,
Abstract: Speech coding techniques capable of generating encoded representations which are robust against channel losses play an important role in enabling reliable voice communication over packet networks and mobile wireless systems. In this paper, we investigate the use of multiple description index assignments (MDIAs) for loss-tolerant transmission of line spectral frequency (LSF) coefficients, typically generated by state-of-the-art speech coders. We propose a simulated annealing-based approach for optimizing MDIAs for Markov-model-based decoders which exploit inter- and intraframe correlations in LSF coefficients to reconstruct the quantized LSFs from coded bit streams corrupted by channel losses. Experimental results are presented which compare the performance of a number of novel LSF transmission schemes. These results clearly demonstrate that Markov-model-based decoders, when used in conjunction with optimized MDIA, can yield average spectral distortion much lower than that produced by methods such as interleaving/interpolation, commonly used to combat the packet losses.
Diagnosis and Management of Elder Abuse by Family Physician  [PDF]
Virginie Dumortier, Humbert de Freminville
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.26049
Abstract: The purpose of this study is to investigate the difficulties encountered by primary care physicians in diagnosing and handling elderly abuse. A survey of the practice of 266 family physicians in France was conducted by email using a questionnaire during the fall of 2012. Statistical analysis was performed using a Chi-2 test for the comparison of two qualitative variables, and the Kruskal-Wallis test was used to compare a qualitative variable with an ordinal one. 77 physicians responded to the questionnaire. They are often faced with the phenomenon of mistreatment, including psychological abuse, of elderly people. They describe the diagnosis correctly but express management difficulties. These difficulties are due to lack of knowledge of the law and a lack of practical tools usable on a daily basis. These physicians call for better training regarding the law and clearer reporting procedures. Education and training in the legislative field must be improved. This conclusion has been reached before in previous surveys in the USA and Europe since the 1970s, which leads to the question as to whether full comprehension of the magnitude of the issue exists. Perhaps the complexity of medical practice requires that an anthropological approach should be taken to identify all the facets involved.
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