Figure 2. Sample path simulations of the two-dimensional stochastic process.
We consider a stochastic process governing the evolution of fitness values of cells within the compartment (see Fig. 1) coupled with a stochastic process representing aging and death of the patient. The figure shows two sample path simulations of this two-dimensional process. The fitness of cells within the compartment is shown on the horizontal axis, and the lifetime of the patient is displayed on the vertical axis. If the trajectory hits the right boundary before reaching the upper border, then cancer initiation occurs before death of the patient (sample path (1)); if the trajectory hits the top boundary before reaching the right border, then death occurs before cancer initiation (sample path (2)). The fitness values bounding the area of interest are dictated by the cutoffs for neutral evolution [56].