Result

library(invGauss)
data(d.oropha.rec)
res <- invGauss(formula.mu = Surv(time, status) ~ 1, formula.c = ~ cond + nstage + tstage, data = d.oropha.rec)

# output
Loading required package:survival
Loading required package: splines
Initial estimates:
   est.mu   est.tau     est.c
0.5456892 0.5456892 1.0772870
*************
Running optim....

summary(res)

# output
Call:
invGauss(formula.mu = Surv(time, status) ~ 1,
formula.c = ~cond + nstage + tstage, data = d.oropha.rec)

Coefficients:
                    Value Std. Error         Z
tau             0.5649196 0.21175109  2.667848
(Intercept).mu  0.7475029 0.16206537  4.612354
(Intercept).c   2.0364148 0.25045918  8.130725
cond.c         -0.6854421 0.10047604 -6.821946
nstage.c       -0.1336489 0.03800133 -3.516953
tstage.c       -0.1897952 0.04978011 -3.812672

Log likelihood: -207.2521

AIC: 426.5043