Fixation probability of the signalling cells as a function of the radius (R) for the one-dimensional non-cumulative model (A–C), and cumulative model (B). A The blue line indicates no cost (c = 0), whereas the red line indicates a positive cost (c = 0.2). (B) Cumulative model is shown in green lines. The presence of cost (c = 0.2) is shown with the dashed line, while absence of cost is given by the continuous line. In all cases the benefit was (b = 0.8). For A,B. L = 50. The fixation probability can be below the neutral expectation (given by the horizontal dashed line) only at large values of R and when the signal is costly (c ≠ 0) (C). Low values of L decrease the fixation probability, protecting against cancer. In all cases the system size was NT = 500.