Statistics for Maintenance Modelling: Proportional Hazards and Accelerated Life Models

# Case Study 2 - Survival Data for Cancer Patients¤

The table on the next screen presents survival data on 40 advanced lung cancer patients, taken from a large body of data discussed by Prentice (1973). The main purpose of the study was to compare the effects of two chemotherapy treatments in prolonging survival time. All patients in the group represented here received prior therapy and were then randomly assigned to one of the two treatments, termed "standard" and "test". Survival times t from the start of the treatment for each patient are recorded. Censored observations are marked with an asterisk and correspond to patients who were still alive at the time the data was collected.

A number of covariates were thought to be important in relation to survival time, and these are also shown for each patient.

1. Different patients can have different types of tumours. Here tumours have been classified into four broad types (squamous, small, adeno and large).
2. Each patient is given a performance status at the time of diagnosis. This is a measure of the general medical status on a scale of 0 to 100: 10, 20, and 30 mean that the patient is completely hospitalised; 40, 50, and 60, mean that they are partially confined to hospital; and 70, 80, and 90, mean they are able to care for themselves.
3. The age of the patient.
4. The number of months from diagnosis of lung cancer to entry into the study.