Quality-adjusted survival analysis is a method for evaluating the effects of treatment on survival which allows the consideration of quality of life as well as the quantity of life. For instance, a highly toxic treatment with number of side effects might delay disease recurrence and increase the survival relative to a less toxic treatment. In this type of situation, the trade-off between negative quality-of-life impact and positive quantity-of-life impact of the more toxic therapy should be evaluated when determining which treatment is most probable to advantage a patient. The method precedes by defining the quality function which assigns a 'score' to the patient which is a composite measure of quality and quantity of life both. In common the quality function assigns a small value to the short life with poor quality and high value to the long life with good quality. The assigned scores are then taken in use to calculate quality- adjusted survival times for the analysis.