Table 2.

Model Assumptions For An Average Repair Proficient Colorectal Cancer

Parameter	Assumptions	Comments
driver mutations or rate-limiting stages (k)	the same for all cancers, transformation or growth does not occur until all driver mutations accumulate	value is unknown and is inferred to fit the epidemiology, growth is likely to precede transformation but most mutations likely accumulate in normal stem cells
number of crypts (m)	does not change during life	crypt number may vary between individuals
stem cells per crypt (n)	does not change during life	value is unknown (minimum of one per crypt), inferred to fit the epidemiology.
mutation rate (u)	does not change during life	value may differ between genes but is ~10-10 to 10-9 per base per division
stem cell divisions since birth (d)	constant division rate during life	value is unknown but may be as high as once per day [13]
probability of cancer (p)	no significant time between transformation and diagnosis	data from cancer epidemiology, lag time may vary between patients