mets (version 1.3.11)

survival_twostage: Twostage Survival Model for Multivariate Survival Data

Description

Fits Clayton-Oakes or bivariate Plackett models for bivariate survival data using marginals that are on Cox form. The dependence can be modelled via:

1. Regression design on dependence parameter.

2. Random effects, additive gamma model.

Usage

survival_twostage(
  margsurv,
  data = NULL,
  method = "nr",
  detail = 0,
  clusters = NULL,
  silent = 1,
  weights = NULL,
  theta = NULL,
  theta.des = NULL,
  var.link = 1,
  baseline.iid = 1,
  model = "clayton.oakes",
  marginal.trunc = NULL,
  marginal.survival = NULL,
  strata = NULL,
  se.clusters = NULL,
  numDeriv = 1,
  random.design = NULL,
  pairs = NULL,
  dim.theta = NULL,
  numDeriv.method = "simple",
  additive.gamma.sum = NULL,
  var.par = 1,
  no.opt = FALSE,
  ...
)

Value

An object of class "mets.twostage" containing:

theta

Estimated dependence parameters.

coef

Coefficients.

score

Score vector.

hess

Hessian matrix.

hessi

Inverse Hessian matrix.

var.theta

Variance of theta parameters.

robvar.theta

Robust variance of theta parameters.

loglike

Log-likelihood value.

theta.iid

Influence functions for theta.

model

Model type used.

Arguments

margsurv

Marginal model object.

data

Data frame (must be given).

method

Scoring method: "nr" for lava NR optimizer.

detail

Detail level for output.

clusters

Cluster variable.

silent

Debug information level.

weights

Weights for score equations.

theta

Starting values for variance components.

theta.des

Design for dependence parameters; when pairs are given, the indices of the theta-design for this pair are given in pairs as column 5.

var.link

Link function for variance: 1 for exponential link.

baseline.iid

To adjust for baseline estimation, using phreg function on same data.

model

Model type: "clayton.oakes" or "plackett".

marginal.trunc

Marginal left truncation probabilities.

marginal.survival

Optional vector of marginal survival probabilities.

strata

Strata for fitting (see examples).

se.clusters

Clusters for SE calculation with IID.

numDeriv

To get numDeriv version of second derivative; otherwise uses sum of squared scores for each pair.

random.design

Random effect design for additive gamma model; when pairs are given, the indices of the pairs' random.design rows are given as columns 3:4.

pairs

Matrix with rows of indices (two-columns) for the pairs considered in the pairwise composite score; useful for case-control sampling when marginal is known.

dim.theta

Dimension of the theta parameter for pairs situation.

numDeriv.method

Method for numerical derivative (e.g., "simple" to speed up things).

additive.gamma.sum

For two.stage=0, this is specification of the lamtot in the models via a matrix that is multiplied onto the parameters theta (dimensions = number of random effects \(\times\) number of theta parameters); when NULL, sums all parameters.

var.par

Is 1 for the default parametrization with the variances of the random effects; var.par=0 specifies that the \(\lambda_j\)'s are used as parameters.

no.opt

For not optimizing.

...

Additional arguments to maximizer NR of lava.

Author

Thomas Scheike

Details

If clusters contain more than two subjects, a composite likelihood based on pairwise bivariate models is used (for full MLE see twostageMLE).

The two-stage model is constructed such that, given gamma distributed random effects, the survival functions are assumed independent, and the marginal survival functions are on Cox form: $$ P(T > t| x) = S(t|x)= \exp( -\exp(x^T \beta) A_0(t) ) $$

One possibility is to model the variance within clusters via a regression design, specifying a regression structure for the independent gamma distributed random effect for each cluster, such that the variance is given by: $$ \theta = h( z_j^T \alpha) $$ where \(z\) is specified by theta.des, and a possible link function var.link=1 will use the exponential link \(h(x)=\exp(x)\), and var.link=0 the identity link \(h(x)=x\).

The reported standard errors are based on the estimated information from the likelihood assuming that the marginals are known (unlike twostageMLE and for the additive gamma model below).

Can also fit a structured additive gamma random effects model, such as the ACE, ADE model for survival data. In this case, the random.design specifies the random effects for each subject within a cluster. This is a matrix of 1's and 0's with dimension \(n \times d\) (for \(d\) random effects).

For a cluster with two subjects, the random.design rows are \(v_1\) and \(v_2\). Such that the random effect for subject 1 is $$v_1^T (Z_1,...,Z_d)$$, for \(d\) random effects. Each random effect has an associated parameter \((\lambda_1,...,\lambda_d)\). By construction, subject 1's random effect is Gamma distributed with mean \(\lambda_j/v_1^T \lambda\) and variance \(\lambda_j/(v_1^T \lambda)^2\). Note that the random effect \(v_1^T (Z_1,...,Z_d)\) has mean 1 and variance \(1/(v_1^T \lambda)\). It is assumed that \(lamtot=v_1^T \lambda\) is fixed within clusters as it would be for the ACE model.

Based on these parameters, the relative contribution (the heritability, \(h\)) is equivalent to the expected values of the random effects: \(\lambda_j/v_1^T \lambda\).

The DEFAULT parametrization (var.par=1) uses the variances of the random effects: $$ \theta_j = \lambda_j/(v_1^T \lambda)^2 $$ For alternative parametrizations, specify how the parameters relate to \(\lambda_j\) with the argument var.par=0.

For both types of models, the basic model assumptions are that given the random effects of the clusters, the survival distributions within a cluster are independent and on the form: $$ P(T > t| x,z) = \exp( -Z \cdot \text{Laplace}^{-1}(lamtot,lamtot,S(t|x)) ) $$ with the inverse Laplace of the gamma distribution with mean 1 and variance \(1/lamtot\).

The parameters \((\lambda_1,...,\lambda_d)\) are related to the parameters of the model by a regression construction pard (\(d \times k\)), that links the \(d\) \(\lambda\) parameters with the \(k\) underlying \(\theta\) parameters: $$ \lambda = theta.des \times \theta $$ here using theta.des to specify these low-dimension associations. Default is a diagonal matrix. This can be used to make structural assumptions about the variances of the random-effects as is needed for the ACE model for example.

The case.control option can be used with the pair specification of the pairwise parts of the estimating equations. Here it is assumed that the second subject of each pair is the proband.

References

• Twostage estimation of additive gamma frailty models for survival data. Scheike (2019), work in progress.

• Shih and Louis (1995) Inference on the association parameter in copula models for bivariate survival data, Biometrics.

• Glidden (2000), A Two-Stage estimator of the dependence parameter for the Clayton Oakes model, LIDA.

• Measuring early or late dependence for bivariate twin data. Scheike, Holst, Hjelmborg (2015), LIDA.

• Estimating heritability for cause specific mortality based on twins studies. Scheike, Holst, Hjelmborg (2014), LIDA.

• Additive Gamma frailty models for competing risks data. Eriksson and Scheike (2015), Biometrics.

Examples

data(diabetes)

# Marginal Cox model  with treat as covariate
margph <- phreg(Surv(time,status)~treat+cluster(id),data=diabetes)
### Clayton-Oakes, MLE
fitco1<-twostageMLE(margph,data=diabetes,theta=1.0)
summary(fitco1)

 ## Reduce Ex.Timings
### Plackett model
mph <- phreg(Surv(time,status)~treat+cluster(id),data=diabetes)
fitp <- survival_twostage(mph,data=diabetes,theta=3.0,Nit=40,
               clusters=diabetes$id,var.link=1,model="plackett")
summary(fitp)

### Clayton-Oakes
fitco2 <- survival_twostage(mph,data=diabetes,theta=0.0,detail=0,
                 clusters=diabetes$id,var.link=1,model="clayton.oakes")
summary(fitco2)
fitco3 <- survival_twostage(margph,data=diabetes,theta=1.0,detail=0,
             clusters=diabetes$id,var.link=0,model="clayton.oakes")
summary(fitco3)

### without covariates but with stratafied
marg <- phreg(Surv(time,status)~+strata(treat)+cluster(id),data=diabetes)
fitpa <- survival_twostage(marg,data=diabetes,theta=1.0,
                clusters=diabetes$id,model="clayton.oakes")
summary(fitpa)


### Piecewise constant cross hazards ratio modelling
########################################################

d <- subset(sim_ClaytonOakes(1000,2,0.5,0,stoptime=2,left=0),!truncated)
udp <- piecewise_twostage(c(0,0.5,2),data=d,method="optimize",
                          id="cluster",timevar="time",
                          status="status",model="clayton.oakes",silent=0)
summary(udp)


 ## Reduce Ex.Timings
### Same model using the strata option, a bit slower
########################################################
## makes the survival pieces for different areas in the plane
##ud1=surv_boxarea(c(0,0),c(0.5,0.5),data=d,id="cluster",timevar="time",status="status")
##ud2=surv_boxarea(c(0,0.5),c(0.5,2),data=d,id="cluster",timevar="time",status="status")
##ud3=surv_boxarea(c(0.5,0),c(2,0.5),data=d,id="cluster",timevar="time",status="status")
##ud4=surv_boxarea(c(0.5,0.5),c(2,2),data=d,id="cluster",timevar="time",status="status")

## everything done in one call
ud <- piecewise_data(c(0,0.5,2),data=d,timevar="time",status="status",id="cluster")
ud$strata <- factor(ud$strata);
ud$intstrata <- factor(ud$intstrata)

## makes strata specific id variable to identify pairs within strata
## se's computed based on the id variable across strata "cluster"
ud$idstrata <- ud$id+(as.numeric(ud$strata)-1)*2000

marg2 <- timereg::aalen(Surv(boxtime,status)~-1+factor(num):factor(intstrata),
               data=ud,n.sim=0,robust=0)
tdes <- model.matrix(~-1+factor(strata),data=ud)
fitp2 <- survival_twostage(marg2,data=ud,se.clusters=ud$cluster,clusters=ud$idstrata,
                model="clayton.oakes",theta.des=tdes,step=0.5)
summary(fitp2)

### now fitting the model with symmetry, i.e. strata 2 and 3 same effect
ud$stratas <- ud$strata;
ud$stratas[ud$strata=="0.5-2,0-0.5"] <- "0-0.5,0.5-2"
tdes2 <- model.matrix(~-1+factor(stratas),data=ud)
fitp3 <- survival_twostage(marg2,data=ud,clusters=ud$idstrata,se.cluster=ud$cluster,
                model="clayton.oakes",theta.des=tdes2,step=0.5)
summary(fitp3)

### same model using strata option, a bit slower
fitp4 <- survival_twostage(marg2,data=ud,clusters=ud$cluster,se.cluster=ud$cluster,
                model="clayton.oakes",theta.des=tdes2,step=0.5,strata=ud$strata)
summary(fitp4)


 ## Reduce Ex.Timings
### structured random effects model additive gamma ACE
### simulate structured two-stage additive gamma ACE model
data <- sim_ClaytonOakes_twin_ace(2000,2,1,0,3)
out <- twin_polygen_design(data,id="cluster")
pardes <- out$pardes
pardes
des.rv <- out$des.rv
head(des.rv)
aa <- phreg(Surv(time,status)~x+cluster(cluster),data=data,robust=0)
ts <- survival_twostage(aa,data=data,clusters=data$cluster,detail=0,
	       theta=c(2,1),var.link=0,step=0.5,
	       random.design=des.rv,theta.des=pardes)
summary(ts)