GI tumor kinetics for three MMR knockout mouse genotypes. For each genotype, both alleles at each locus were knocked out. a Kaplan-Meier estimate  at each age of the fraction of mice that have not yet developed GI tumors among the population of mice that remain at risk. b Smoothed curve fit to the estimated survival curve in a using the smooth.spline function of the R computing language  with the smoothing parameter set to 0.5. c Incidence of GI tumors on log-log scales. d The acceleration of tumor onset calculated from the slope of the lines in c. Each column of plots corresponds to one of the three methods for dealing with the 7 observed GI carcinomas; we explained the different methods in the text. In our calculations, we truncated the curves at survival fractions below 0.2 because the errors in incidence estimates rise rapidly at low levels of survival. The spreadsheet included in the supplemental materials provides a full listing of the data used to generate Figures 1 and 2.