The use of prognostic factors in predicting survival for breast cancer patients

Using statistical methods for analyzing factorial experiments, it was found that each of the four variables influenced survival and that the order of importance was axillary node status, tumor size, sinus histiocytosis and nuclear grade.

Abstract

There were 375 cases in the series of breast cancer patients diagnosed from 1921 to 1953 at the Yale-New Haven Medical Center for which information was available for the following four variables: axillary lymph node status, nuclear grade, sinus histiocytosis and tumor size. Patients were classified according to a favorable or unfavorable status with respect to each of these four variables. With one exception, the survival distribution for the 16 resulting groups of patients could be reasonably approximated by a simple exponential distribution. This implies that the mortality rate can be used for analytical purposes as a summary of the survival pattern for a group of cases. Using statistical methods for analyzing factorial experiments, we found that each of the four variables influenced survival and that the order of importance was axillary node status, tumor size, sinus histiocytosis and nuclear grade. No interaction was judged important. Based on an assumption of exponential survival, a mathematical model was developed which made meaningful survival prediction possible (by taking disease status at time of mastectomy into account). The mathematical model was further used for ranking combinations of conditions of the four variables in order of prognostic importance.