CHEUVART, B & RYAN, L 1991, 'ADJUSTING FOR AGE-RELATED COMPETING MORTALITY IN LONG-TERM CANCER CLINICAL-TRIALS', STATISTICS IN MEDICINE, vol. 10, no. 1, pp. 65-77.
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Mortality related to causes other than the treated disease may have a significant impact on overall survival in long‐term clinical trials. We present a model that adjusts for age‐related competing mortality when cause of death is missing or only partially available. Through use of a piecewise exponential survival model, we extend relative survival methods to continuous follow‐up data, allowing the competing mortality to differ from that of the general population by a scale parameter. An EM algorithm provides a simple way to compute the maximum likelihood estimators (MLEs) and to test hypotheses using widely available software. We compare the bias and relative efficiency of this model to a piecewise exponential Cox model for overall survival. Theoretical results are confirmed by simulations and illustrated with data from a clinical trial in colorectal cancer. This example also shows how age‐related and disease‐related mortality can be confounded in an analysis of overall survival. We conclude with a discussion of the advantages and dis‐advantages of the model. Copyright © 1991 John Wiley & Sons, Ltd.
ENGSTROM, PF, RYAN, LM, FALKSON, G & HALLER, DG 1991, 'PHASE-II STUDY OF AMINOTHIADIAZOLE IN ADVANCED SQUAMOUS-CELL CARCINOMA OF THE ESOPHAGUS', AMERICAN JOURNAL OF CLINICAL ONCOLOGY-CANCER CLINICAL TRIALS, vol. 14, no. 1, pp. 33-35.
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Twenty-three patients with advanced inoperable squamous cell carcinoma of the esophagus were treated with aminothiadiazole (A-TD) 125 mg/m2 weekly plus allopurinol daily in a phase II cooperative group trial. No patients responded to treatment; 17 patien
RYAN, LM, CATALANO, PJ, KIMMEL, CA & KIMMEL, GL 1991, 'RELATIONSHIP BETWEEN FETAL WEIGHT AND MALFORMATION IN DEVELOPMENTAL TOXICITY STUDIES', TERATOLOGY, vol. 44, no. 2, pp. 215-223.
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Exposure to developmental toxicants may cause fetal malformations, increase prenatal death rates and reduce fetal weight at term. However, there has been little formal study of the relationship among these effects. Certainly, no statistical methods are currently available to jointly analyze these effects of exposure. As a preliminary step in developing such methods, simple exploratory analyses were conducted using a series of ten studies conducted for the National Toxicology Program. Because fetal weight and malformation status were both reported for all live fetuses, the data permitted an exploration of the correlation between these two outcomes. The data show a clear pattern wherein malformed fetuses tended to be lighter at term than nonmalformed fetuses. While these patterns cannot be used to draw inferences regarding the biological relationship between fetal weight and malformation, they do suggest the potential value in developing statistical models for the joint effect of exposure on fetal weight and malformations. Copyright © 1991 Wiley‐Liss, Inc., A Wiley Company
Zhang, C & Bell, DA 1991, 'HECODES: a framework for HEterogeneous COoperative distributed expert systems', Data & Knowledge Engineering, vol. 6, no. 3, pp. 251-273.
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Cooperation between human experts is important when solving many complex problems and communication between the experts is essential for such cooperation. Cooperation between computerised expert systems is equally essential when dealing with complex problems. The software system described in this paper, HECODES (HEterogeneos COoperative Distributed Expert Systems), is a framework used to realize cooperation between distributed heterogeneous expert systems (ESs). HECODES consists of a centralized control system, a blackboard system, and front-end processors. All parts of HECODES are specified (and implemented) using knowledge-based programming techniques and so they are domain-independent. HECODES can integrate a variety of pre-existing ESs using a variety of kinds of cooperation. The ESs can be heterogeneous with respect to control strategy, knowledge representation, and programming language. A prototype has been implemented using Common Lisp on a network of DEC VAX machines some of which are 60 miles apart. This paper presents the architecture of HECODES and describes the approach it takes to the provision of cooperation, knowledge-based scheduling, domain-independent communication, deadlock treatment, homomorphic transformation of heterogeneous inexact reasoning models, and the synthesis of solutions. © 1991.
