Showing papers on "Subgroup analysis published in 1995"

Interferon-alpha and survival in renal cell cancer.

Abstract: Objective To establish whether the use of interferonalpha might result in improved survival, using two large series of patients with advanced renal cell cancer treated during studies of chemotherapy and biological therapy, respectively. Patients and methods Patients treated either in the Eastern Cooperative Oncology Group (ECOG) chemotherapy protocols (327 patients) or in protocols employing interferon as part of a European randomized study or phase II studies at the Norwegian Radium Hospital (231 patients) were retrospectively analysed. Groups for comparison were matched by exclusion of those with an ECOG performance status >2, no prior nephrectomy, brain metastases or prior chemotherapy. Univariate analysis of prognostic factors for survival was performed by the log rank method and multivariate analysis by Cox regression. Results Univariate analysis of the whole population showed that performance status, time from diagnosis to treatment, sites of metastases and the use of interferon carried the greatest prognostic significance. In multivariate analysis, the use of interferon remained a significant predictor of survival (P < 0.001). Subgroup analysis suggested that the impact of interferon treatment was greatest in those patients with two of the following characteristics; good performance status, an interval of < 2 years from diagnosis to treatment and no more than one site of metastasis. Conclusion Although a prospective randomized trial is needed to establish definite benefit from the use of interferon in advanced renal cell cancer, this analysis supports the rationale for performing such a trial, particularly in patients with relatively good prognostic features. Patients should be entered into the Medical Research Council study comparing interferon with medroxyprogesterone acetate.

Prediction and decision making using Bayesian hierarchical models

Abstract: This paper uses Bayesian hierarchical models to analyse multi-centre clinical trial data where the outcome variable of interest is continuous, but not normally distributed, and where censoring has occurred. The goal of such an analysis is the same as for any subgroup analysis, to provide survival estimates for specific subgroups as well as for the population and to provide estimates of the degree of heterogeneity between subgroups. An analysis of the Collaborative Study of Long-Term Maintenance Drug Therapy in Recurrent Affective Illness, a multi-centre clinical trial funded by the National Institute for Mental Health's Pharmacologic Research Branch, serves to illustrate the proposed methodology. A feature of this data set is that one treatment group was withdrawn from medication at the time of randomization. The paper contains comparison of models, one that accounts for the drug washout period through the use of a changepoint model as well as a comparison of results across several choices of prior parameter values. In addition, the paper considers sensitivity to model choice and priors in a decision theory context.

Mammographic Screening for Women Aged 40 to 49 Years: The Primary Care Practitioner's Dilemma

Abstract: The data from population-based, randomized trials of the mammographic screening of women aged 40 to 49 years are limited by retrospective subgroup analysis, low statistical power, and the use of ol...

How should zoster trials be conducted

Abstract: In 1994, an international group of interested clinicians and biostatisticians met to discuss the design of clinical trials in herpes zoster. They agreed that trials in herpes zoster should have prospectively agreed definitions of all outcome measures and plans for data analysis. In immunocompetent individuals, in whom pain is the major outcome measure, trials should only include patients over the age of 50 years, and for those recruited within 72 h of rash onset, should be designed to demonstrate superiority of any new therapy over existing antivirals. The primary endpoint should be time to cessation of pain for at least 4 weeks and, for the purposes of statistical analysis of its duration, the pain associated with herpes zoster ought to be considered as a continuum. All other variables, including the incidence of post-herpetic neuralgia and effects upon quality of life should be considered as secondary end-points. Evaluation of treatment effects on primary endpoints should be based upon an intent-to-treat (ITT) analysis and subgroup analysis should be used only to support the findings of the ITT analysis. These elements of good study design should be borne in mind in the evaluation of current and future trails of antiviral drugs in herpes zoster.

Treatment for survivors of acute myocardial infarction: what have we learned from large intervention trials?

Abstract: The current treatment of survivors of acute myocardial infarction is now largely based on sound scientific principles, supported by the results of large and well-designed clinical trials. These have demonstrated that aspirin, anticoagulants, beta-blockers, angiotensin converting enzyme inhibitors, and lipid-lowering agents reduce mortality and reinfarction in selected groups of patients. It remains uncertain whether these different treatments are additive and whether there are beneficial or undesirable interactions. In addition to informing us about the effectiveness or otherwise of these and other drugs, we have learned much about the conduct, analysis, and limitations of clinical trials in this context. The selection of patients for the various treatments is a matter of opinion because the results of the trials are open to a variety of interpretations. In assessing trials, one must be sure that they have been conducted on the intention to treat principle and that surrogate and composite end points have not been inappropriately used. In applying the results of trials to one's own practice, one must take into account the problems of extrapolation and subgroup analysis.

Subgroup determination of group A rotaviruses recovered from piglets in Nigeria.

Abstract: Subgroup analysis using subgroup-specific monoclonal ELISA revealed a preponderance of subgroup 2-specific antigens of group A porcine rotaviruses over subgroup 1. Of 113 polyacrylamide gel electrophoresis-positive test samples, obtained from 4 States of Nigeria, 31 (27.4%) and 45 (39.8%) were determined to have subgroup 1 and 2 specificities, respectively. However, 37 (32.7%) test samples could not be classified into any of the known group A rotavirus subgroups. These "unclassifiable" samples probably had neither subgroup 1 nor 2 specificities in ELISA or could belong to a third subgroup unknown or not investigated in this study. In all age groups investigated, subgroup 1 and 2 specific antigens were prevalent. This was also observed after yearly analysis of subgroup specificity; however, a higher prevalence of subgroup 2 specificity was observed in 1990 and 1991. Subgroup 1 rotaviruses were found in all the 4 States sampled (Plateau, Benue, Oyo, and Cross River), whereas subgroup 2 rotaviruses were detected only in Plateau State. All rotaviruses recovered in this study had long genome electrophoretic migration patterns, irrespective of subgroup. Thus genomic diversity of group A rotaviruses does not necessarily reflect antigenic diversity, as there is no mandatory correlation between genome electropherotype pattern and subgroup specificity.

CAD Progression Not Halted by Antioxidants

Abstract: Previous studies have suggested that antioxidant vitamins can reduce coronary artery disease (CAD) risk. This retrospective subgroup analysis of the Cholesterol Lowering Atherosclerosis Study (CLAS) -- a randomized, placebo-controlled, serial angiographic trial that evaluated the effect of colestipol-niacin treatment on CAD progression -- tried to determine whether antioxidants can reduce progression of atherosclerotic …