The dataset contains cases from a study that was conducted between 1958 and 1970 at the University of Chicago's Billings Hospital on the survival of patients who had undergone surgery for breast cancer.
Attribute Information:  
1. Age of patient at time of operation (numerical) 
2. Patient's year of operation (year - 1900, numerical) 
3. Number of positive axillary nodes detected (numerical) 
4. Survival status (class attribute) -- 1 = the patient survived 5 years or longer -- 2 = the patient died within 5 year