The risk of chemotherapy.

Human survival curves may be classified according to the magnitudes of their hazard rate derivatives into three elementary shapes or groups: Aging (lambda' (t) greater than 0), random death (lambda' (t) = 0) and regeneration (lambda' (t) less than 0). Each observed survival curve is assumed to be composed of one or more elementary shapes. The aging pattern is observed in population cohorts from the age of 15 years and onward. It underlies survival curves of experimental animal treated by whole body irradiation which is assumed to act via the nervous system inducing generalized hypoplasia by impeding its trophic function. The whole process is manifested by an increasing lambda (t). Regeneration, is associated with the mobilization of reserves to withstand a noxious perturbation. The regeneration pattern is observed in patients surviving myocardial infarction, or recovering from surgical intervention. It is shared also by all survival curves of the 4th report on end results of cancer, and is assumed to reflect the beneficial role of neoplasia. While the hazard rate lambda (t) reflects mortality, its derivative lambda' (t) is viewed here as a measure of morbidity, so that cancer treatment effectiveness has to be assessed by its influence on both. A beneficial treatment ought to reduce them and vice versa. Most survival curves published in the modern cancer literature indicate an increasing morbidity accompanying treatment manifested by a positive hazard rate derivative (lambda' (t) greater than 0).