The incubation time of cancer.

Incubation times of cancers whose initiation can be estimated relatively, precisely are distributed log-normally. This distribution is associated with a biphasic risk function, initially climbing to decline again after a certain period. A declining risk of contracting cancer implies further that the patient's chances of withstanding cancer improve with time. A similar declining risk function was also observed in age specific cancer incidence curves. At the age of 30 years they all rise exponentially to level off at old age. In some cancers e.g. bronchial or female genital, the curves even decline. The risk functions associated with them follow a similar course. Such may not be the case in some chronic systemic diseases, e.g. arteriosclerosis, in which the risk function never declines so that the patient's resistance to this disease is smaller than that observed in cancer. The declining risk proceeds even during the clinical phase of cancer as evident from two sources o data 1. Age specific cancer mortality curves exhibit the same pattern associated with a biphasic risk function and, 2. survival curves of cancer patients inhibit a declining risk function. The mounting resistance with time observed in cancer is observable in any disease, infectious as well chronic systemic.