Statistics in medicine
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Statistics in medicine · Sep 2008
Factors affecting enrollment in literacy studies for English- and Spanish-speaking cancer patients.
Study participation bias can affect inferences regarding outcomes. ⋯ Spanish-speaking patients enrolled at a much higher rate than English-speaking patients, which is encouraging for future research in this underserved population. One important literacy-related factor (education) did not affect enrollment in Spanish-speaking patients, suggesting that there was no selection bias in this study. Recruiting sites with more indigent patients and long clinic waiting times had higher enrollment, suggesting that monetary compensation and time availability may be important considerations in study participation.
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Statistics in medicine · Aug 2008
A note on the conservativeness of the confidence interval approach for the selection of non-inferiority margin in the two-arm active-control trial.
Compared with placebo-control clinical trials, the interpretation of efficacy results from active-control trials requires more caution. This is because efficacy results from such trials cannot be reliably interpreted without a thorough understanding of the efficacy evidence that formed the basis for the approval of the active control, especially when such drug efficacy is to be established on the basis of clinical evidence from the traditional two-arm active-control clinical equivalence studies as opposed to the multi-arm active control. ⋯ Simulation results are presented to show that the point estimate method provides adequate control of the Type I error rate with > or =75 per cent retention of known active-control effect and that the confidence interval approach is uniformly ultra-conservative. We also report (via a numerical example from real clinical trial data) a couple of potentially less stringent alternative approaches for establishing the non-inferiority of a test drug over a control, which have been used in the past to provide additional efficacy evidence in NDA submission.
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Traditional designs for phase I clinical trials assign the same dose to patients in the same cohort. In this paper, we present a new class of designs for cancer phase I trials which initially rapidly escalate by allowing multiple doses (usually 3) to be assigned to each cohort of patients. ⋯ Three designs (slow, moderate and fast) are derived based on different dose-escalation restrictions. Simulation results show that moderate and fast LMH-CRM combine the advantages of the CRM with one patient per cohort and three patients per cohort: it accurately estimates the MTD; controls overall toxicity rates; and is time efficient.