On the use of hazard functions in breast cancer studies.

Hazard functions are nowadays used extensively by mathematicians as a tool in the analysis of survival data. They have been implicitly employed in medicine for many years to investigate 'curability'. The hazard function will be shown to be a natural concept which can help the clinician to express in a precise way his ideas concerning the disease process and the biology of treatment effect. The relationship between hazard and survivor function is discussed. Some historical comments about the interpretation of statistics in survival time studies are also made.