Abstracts 381

SlO COST UTILITY ANALYSIS OF MAINTENANCE TREATMENT FOR RECURRENT DEPRESSION

Nancy Paul, Mark Kamlet, and Joel Greenhouse Carnegie Mellon University

Pittsburgh, Pennsylvania

The primary objective of a randomized controlled clinical trial (RCT) is to assess the relative efficacy of one treatment or intervention to another. Clinical efficacy of the treatments is usually assessed in terms of improvement in survival time or the proportion of patients responding favorably. Evaluations of clinical efficacy, however, typically do not include the assessment of health economic issues, such as side effects of a treatment or the cost for treatment. Thus, one could study two treatments and conclude that they performed equally well in the prevention of the occurrence of some disease, say, while in fact one treatment might have a number of side effects or be prohibitively expensive. Hence, while survival analysis techniques are useful in assessing the clinical efficacy of different treatments, such analyses say nothing about the trade-offs between improvement in health and cost in dollars for the various treatments. To make such a determination, one would have to adopt a cost-utility analysis (CUA) approach. CUA evaluates a health intervention by comparing the incremental societal costs of a health intervention and the incremental health benefits. The purpose of this paper is to illustrate the use of a CUA using data from a three-year RCT to evaluate a maintenance pharmacotherapy versus a maintenance psychotherapy for the prevention of the recurrence of depression.

Sil THE ANALYSIS OF INCOMPLETE DATA IN THE THREE-PERIOD TWO-TREATMENT CROSSOVER

DESIGN FOR CLINICAL TRIALS

Barbra Rlchardson UCLA

Los Angeles, California

Two-period two-treatment (2P2T) crossover designs are frequently implemented for the comparison of therapeutic treatments in clinical trials. However, intrinsic faults with the 2P2T crossover designs lead to many problems when analyzing data from such designs. Thus, recent research has centered on the three-period two-treatment (3P2T) crossover designs. The addition of an extra period by implementing a 3P2T crossover design reduces some of the problems with the analysis of the data. But the additional time needed to complete a 3P2T crossover trial may cause a greater number of the subjects to drop out of the clinical trial before completion. The lack of literature on remedies for problems with missing data in the 3P2T crossover designs suggests a need for the development of missing data analysis methods for clinical trials using such designs.

This paper develops the maximum likelihood and the multiple imputation missing data analysis methods for the 3P2T crossover designs. These methods are then compared and contrasted both with each other and with the standard method of missing data analysis for crossover trials, the complete case method.

s12 PROGNOSTIC INDICES: WHO NEEDS THEM?

Janet A. Dunn University of Birmingham

Birmingham, England

The development of new prognostic indices (PI’s) is an important issue in cancer clinical trials. For disease sites such as resectable gastric cancer, myelomatosis and early breast cancer the standard treatments have not altered over recent years. Data from such studies may be used to develop PI’s which identify subgroups of patients for whom the treatment was beneficial or, conversely, ineffective.

There are many practical and theoretical difficulties in developing reliable PI’s, which may affect repro- ducibility. Data from several different clinical trials may not be comparable because of the way data were collected or due to differences inherent in the trial design. The Cox proportional hazards model is commonly used to determine independent prognostic factors which have an influence on survival. The proportionality assumption of this model can be tested graphically but can be subjective. Goodness of fit tests have been presented in the literature and should be always applied to these models.

To illustrate the importance of PI’s and the possible pitfalls, data are presented from a retrospective study