R: Neurodegenerative disease simulated longitudinal dose-finding...

neurodeg {DoseFinding} | R Documentation

## Neurodegenerative disease simulated longitudinal dose-finding data set

### Description

This simulated data set is motivated by a real Phase 2 clinical study of a new drug for a neurodegenerative disease. The state of the disease is measured through a functional scale, with smaller values corresponding to more severe neurodeterioration. The goal of the drug is to reduce the rate of disease progression, which is measured by the linear slope of the functional scale over time.

The trial design includes placebo and four doses: 1, 3, 10, and 30 mg, with balanced allocation of 50 patients per arm. Patients are followed up for one year, with measurements of the functional scale being taken at baseline and then every three months.

The functional scale response is assumed to be normally distributed and, based on historical data, it is believed that the longitudinal progression of the functional scale over the one year of follow up can be modeled a simple linear trend. See the example below on how to analyse this type of data.

This data set was used in Pinheiro et al. (2013) to illustrate the generalized MCPMod methodology.

### Usage

    data(neurodeg)

### Format

A data frame with 100 observations on the following 2 variables.

`resp`

  a numeric vector containing the response values

`dose`

  a numeric vector containing the dose values

`id`

  Patient ID

`time`

  time of measurement

### Source

Pinheiro, J. C., Bornkamp, B., Glimm, E. and Bretz, F. (2014) Model-based dose finding under model uncertainty using general parametric models, Statistics in Medicine, 33, 1646–1661

### Examples

    ## Not run:
    ## reproduce analysis from Pinheiro et al. (2013)
    data(neurodeg)
    ## first fit the linear mixed effect model
    library(nlme)
    fm <- lme(resp ~ as.factor(dose):time, neurodeg, ~time|id)
    muH <- fixef(fm)[-1] # extract estimates
    covH <- vcov(fm)[-1,-1]

    ## derive optimal contrasts for candidate shapes
    doses <- c(0, 1, 3, 10, 30)
    mod <- Mods(emax = 1.11, quadratic= -0.022, exponential = 8.867,
                linear = NULL, doses = doses) #
    contMat <- optContr(mod, S=covH) # calculate optimal contrasts
    ## multiple contrast test
    MCTtest(doses, muH, S=covH, type = "general", critV = TRUE,
            contMat=contMat)
    ## fit the emax model
    fitMod(doses, muH, S=covH, model="emax", type = "general",
           bnds=c(0.1, 10))

    ## alternatively one can also fit the model using nlme
    nlme(resp ~ b0 + (e0 + eM * dose/(ed50 + dose))*time, neurodeg,
         fixed = b0 + e0 + eM + ed50 ~ 1, random = b0 + e0 ~ 1 | id,
         start = c(200, -4.6, 1.6, 3.2))
    ## both approaches lead to rather similar results

    ## End(Not run)

[Package DoseFinding version 0.9-17 Index]