skin: The skin cancer prevention study

In ALA: Data sets and examples for the book "Applied Longitudinal Analysis"

Description

The data are from the Skin Cancer Prevention Study, a randomized, double-blind, placebo-controlled clinical trial of beta-carotene to prevent non-melanoma skin cancer in high risk subjects.

Usage

data(skin)

Format

A data frame with 7081 observations on the following 9 variables.

id

a factor with 1683 levels

center

a factor with levels C1, C2, C3, C4

age

a numeric vector

skin

a factor with levels otherwise and burns

gender

a factor with levels F and M

nExposure

a numeric vector; number of previous skin cancers

nCancers

a numeric vector; number of new skin cancers per year

treatment

a factor with levels placebo and B-carotene

year

a numeric vector; year of follow-up

Details

A total of 1805 subjects were randomized to either placebo or 50mg of beta-carotene per day for 5 years. Subjects were examined once a year and biopsied if a cancer was suspected to determine the number of new skin cancers occurring since the last exam. The outcome variable is a count of the number of new skin cancers per year. The outcome variable Y is a count of the of the number of new skin cancers per year. The categorical variable Treatment is coded 1=beta-carotene, 0=placebo. The variable Year denotes the year of follow-up. The categorical variable Gender is coded 1=male, 0=female. The categorical variable Skin denotes skin type and is coded 1=burns, 0=otherwise. The variable Exposure is a count of the number of previous skin cancers. The variable Age is the age (in years) of each subject at randomization. Complete data are available on 1683 subjects comprising a total of 7081 measurements.

Note

Original variable names have been adapted to R conventions. The center ID was prefixed with the letter “C” in the center variable, compared to the source.

Source

http://biosun1.harvard.edu/~fitzmaur/ala

References

Greenberg ER, Baron JA, Stukel TA, Stevens MM, Mandel JS, Spencer SK, Elias PM, Lowe N, Nierenberg DW, Bayrd G, Vance JC, Freeman DH, Clendenning WE, Kwan T, the Skin Cancer Prevention Study Group (1990) A clinical trial of beta carotene to prevent basal-cell and squamous-cell cancers of the skin. New England Journal of Medicine 323:789-795

Examples

str(skin)
summary(skin)

ALA documentation built on May 2, 2019, 5:39 p.m.