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21.
Anh Nguyen Duc Dominik Heinzmann Claude Berge Marcel Wolbers 《Pharmaceutical statistics》2021,20(2):202-211
One of the challenges in the design of confirmatory trials is to deal with uncertainties regarding the optimal target population for a novel drug. Adaptive enrichment designs (AED) which allow for a data-driven selection of one or more prespecified biomarker subpopulations at an interim analysis have been proposed in this setting but practical case studies of AEDs are still relatively rare. We present the design of an AED with a binary endpoint in the highly dynamic setting of cancer immunotherapy. The trial was initiated as a conventional trial in early triple-negative breast cancer but amended to an AED based on emerging data external to the trial suggesting that PD-L1 status could be a predictive biomarker. Operating characteristics are discussed including the concept of a minimal detectable difference, that is, the smallest observed treatment effect that would lead to a statistically significant result in at least one of the target populations at the interim or the final analysis, respectively, in the setting of AED. 相似文献
22.
We present a new semi-parametric model for the prediction of implied volatility surfaces that can be estimated using machine
learning algorithms. Given a reasonable starting model, a boosting algorithm based on regression trees sequentially minimizes
generalized residuals computed as differences between observed and estimated implied volatilities. To overcome the poor predictive
power of existing models, we include a grid in the region of interest, and implement a cross-validation strategy to find an
optimal stopping value for the boosting procedure. Back testing the out-of-sample performance on a large data set of implied
volatilities from S&P 500 options, we provide empirical evidence of the strong predictive power of our model. 相似文献
23.
The rate of convergence in the central limit theorem and in the random central limit theorem for some functions of U-statistics are established. The theorems refer to the asymptotic behaviour of the sequence {g(Un),n≥1}, where g belongs to the class
of all differentiable functions g such that g′εL(δ) and Un is a U-statistics. 相似文献
24.
For a trial with primary endpoint overall survival for a molecule with curative potential, statistical methods that rely on the proportional hazards assumption may underestimate the power and the time to final analysis. We show how a cure proportion model can be used to get the necessary number of events and appropriate timing via simulation. If phase 1 results for the new drug are exceptional and/or the medical need in the target population is high, a phase 3 trial might be initiated after phase 1. Building in a futility interim analysis into such a pivotal trial may mitigate the uncertainty of moving directly to phase 3. However, if cure is possible, overall survival might not be mature enough at the interim to support a futility decision. We propose to base this decision on an intermediate endpoint that is sufficiently associated with survival. Planning for such an interim can be interpreted as making a randomized phase 2 trial a part of the pivotal trial: If stopped at the interim, the trial data would be analyzed, and a decision on a subsequent phase 3 trial would be made. If the trial continues at the interim, then the phase 3 trial is already underway. To select a futility boundary, a mechanistic simulation model that connects the intermediate endpoint and survival is proposed. We illustrate how this approach was used to design a pivotal randomized trial in acute myeloid leukemia and discuss historical data that informed the simulation model and operational challenges when implementing it. 相似文献
25.
Health-related well-being is a result of individual or collective agency. Understanding and influencing health-relevant behaviour, however, requires to account for physical and social contexts of agency. Accordingly, the authors suggest a focus in modern health promotion on people’s health-relevant resources and capabilities. This requires a theoretical basis onto which issues of social inequality can be linked to specific approaches of health promotion practice, namely empowerment and participation. To this purpose, the authors present Amartya Sen’s theory-based Capability Approach (CA) and complement it with insights from Pierre Bourdieu’s theory of capital interaction. Both of these theories shed light on key issues of social inequality and can fruitfully be associated with the guiding principles in health promotion stipulated by the Ottawa Charter. Together, they provide guidelines for new areas of research to analyse the complex interplay between health behaviour and social context. 相似文献
26.
In this paper the interest is in testing the null hypothesis of positive quadrant dependence (PQD) between two random variables. Such a testing problem is important since prior knowledge of PQD is a qualitative restriction that should be taken into account in further statistical analysis, for example, when choosing an appropriate copula function to model the dependence structure. The key methodology of the proposed testing procedures consists of evaluating a “distance” between a nonparametric estimator of a copula and the independence copula, which serves as a reference case in the whole set of copulas having the PQD property. Choices of appropriate distances and nonparametric estimators of copula are discussed, and the proposed methods are compared with testing procedures based on bootstrap and multiplier techniques. The consistency of the testing procedures is established. In a simulation study the authors investigate the finite sample size and power performances of three types of test statistics, Kolmogorov–Smirnov, Cramér–von‐Mises, and Anderson–Darling statistics, together with several nonparametric estimators of a copula, including recently developed kernel type estimators. Finally, they apply the testing procedures on some real data. The Canadian Journal of Statistics 38: 555–581; 2010 © 2010 Statistical Society of Canada 相似文献
27.
Suresh H. Moolgavkar Jay Turim Dominik D. Alexander Edmund C. Lau Colleen A. Cushing 《Risk analysis》2010,30(8):1240-1248
We reanalyzed the Libby vermiculite miners’ cohort assembled by Sullivan to estimate potency factors for lung cancer, mesothelioma, nonmalignant respiratory disease (NMRD), and all‐cause mortality associated with exposure to Libby fibers. Our principal statistical tool for analyses of lung cancer, NMRD, and total mortality in the cohort was the time‐dependent proportional hazards model. For mesothelioma, we used an extension of the Peto formula. For a cumulative exposure to Libby fiber of 100 f/mL‐yr, our estimates of relative risk (RR) are as follows: lung cancer, RR = 1.12, 95% confidence interval (CI) =[1.06, 1.17]; NMRD, RR = 1.14, 95% CI =[1.09, 1.18]; total mortality, RR = 1.06, 95% CI =[1.04, 1.08]. These estimates were virtually identical when analyses were restricted to the subcohort of workers who were employed for at least one year. For mesothelioma, our estimate of potency is KM = 0.5 × 10?8, 95% CI =[0.3 × 10?8, 0.8 × 10?8]. Finally, we estimated the mortality ratios standardized against the U.S. population for lung cancer, NMRD, and total mortality and obtained estimates that were in good agreement with those reported by Sullivan. The estimated potency factors form the basis for a quantitative risk assessment at Libby. 相似文献
28.
29.
European Welfare regimes and the transition to adulthood: A comparative and longitudinal perspective 总被引:1,自引:0,他引:1
Social Indicators Research - 相似文献
30.
Social Indicators Research - 相似文献