It is the proportion of people in a study or treatment group still alive at a given period of time after diagnosis.
It is a method of describing prognosis in certain disease conditions, and can be used for the assessment of standards of therapy.
They often serve as endpoints of clinical trials and should not be confused with mortality rates, a population metric.
Disease-specific survival rate refers to "the percentage of people in a study or treatment group who have not died from a specific disease in a defined period of time.
In ongoing settings such as clinical trials, the median has the advantage that it can be calculated once 50% of subjects have reached the clinical endpoint of the trial, whereas calculation of an arithmetical mean can only be done after all subjects have reached the endpoint.
[4] The median overall survival is frequently used by the U.S. Food and Drug Administration to evaluate the effectiveness of a novel cancer treatment.