ren {frailtyHL}

Mammary tumor data

Description

The data set by presented Gail et al. (1980) is based on multiple occurrences of mammary tumors for 48 female rats. The primary outcome of interest was time to development of a mammary tumor for 23 female rats in the treatment group and 25 female rats in the control group. Initially, 76 rats were injected with a carcinogen for mammary cancer at day zero, and then all rats were given retinyl acetate to prevent cancer for 60 days. After 60 days, forty-eight rats which remained tumor-free were randomly assigned to continue being treated with retinoid prophylaxis (treatment group) or to the control group receiving no further retinoid prophylaxis. Rats were palpated for tumors twice weekly and observation ended 182 days after the initial carcinogen injection. In some cases, there were multiple tumors detected by the same day. The number of tumors ranges from 0 to 13.

Usage

data("ren")

Format

A data frame with 254 observations on the following 6 variables.

rat

Rat id

time1

Start time

time2

Stop time

del

Censoring indicator(1=tumor, 0=censored)

gp

Treatment indicator(1=drug, 0=control)

time

time2-time1 (time=time+0.01 if there are ties)

References

Gail, M.H. Santner, T.J. and Brown, C.C. (1980), An analysis of comparative carcinogenesis experiments based on multiple times to tumor. Biometrics, 36, 255-266.

Ha, I. D., Jeong, J. H. and Lee, Y. (2017). Statistical modelling of survival data with random effects: h-likelihood approach. Springer, in press.