2009 - St. Petersburg - Russia

PAGE 2009: Methodology- Model evaluation
Richard Nixon

Using short-term evidence to predict six-month outcomes in clinical trials of signs and symptoms in rheumatoid arthritis

Richard Nixon

Novartis

Objectives: A model is presented to generate a distribution for the probability of an ACR response at six months for a new treatment for rheumatoid arthritis given evidence from a one or three month clinical trial.

Methods: A model is presented to generate a distribution for the probability of an ACR response at six months for a new treatment for rheumatoid arthritis given evidence from a one or three month clinical trial. We denote j as the treatment arm within each clinical trial, and k the type of treatment used (k=1 for MTX, k=2 for biologic, k=3 for biologic plus MTX); t0 as the earlier time point (either one month or three months depending on the model); and t1 the six-month time point. We then denote nj as the number of patients in treatment arm j for which there is data available at both time points, and rjt as the number of patients achieving the ACR response criteria at time point t. We assume that rjt0 and rjt1 are binomially distributed with parameters φjt0 and φjt1 representing the probabilities of response, respectively. φjt1 is assumed to be dependent upon φjt0, in a logistic regression. To estimate the ACR response rate at time point t1 from the ACR response rate at time point t0, we fit the following statistical model:
rjt0 ~ Binomial(nj, φjt0)
rjt1 ~ Binomial(nj, φjt1)
logit(φjt1) = αj+ βlogit(φjt0)
αj~N(μk, σ2)

Results: The model is assessed by Bayesian predictive P-values that demonstrate that the model fits the data well.

Conclusions: The model can be used to predict the number of patients with an ACR response for proposed six-month clinical trials given data from clinical trials of one or three months duration

References:
[1] Nixon RM, Bansback N, Stevens JW, Brennan A and Madan J. Using short-term evidence as prior information in the design of six-month clinical trials of signs and symptoms in rheumatoid arthritis. Pharmaceutical Statistics. 2008 early view. DOI 10.1002/pst.351




Reference: PAGE 18 (2009) Abstr 1545 [www.page-meeting.org/?abstract=1545]
Poster: Methodology- Model evaluation
Click to open PDF poster/presentation (click to open)
Top