Contrasting the impact of cytotoxic and cytostatic drug therapies on tumour progression
A Primary tumour is assumed to have reached its present growth potential (yellow). It can progress to the next epoch of growth via de novo driver mutation that, for example, induces angiogenesis (red), or via seeding metastasis (blue). B Simulated example trajectories at high (low) cell turnover with β0 = 1.0, δ0 = 0.6, (β0 = 0.42; δ0 = 0.02). Black line shows total population size. Blue line shows metastatic tumour population sizes and red line shows cell population containing driver mutation. Tick marks on the time axis show metastasis and mutation events, some of which go extinct due to fluctuations that are stronger in high turnover tumours. C The simulation experiment setting on a birth rate–death rate plane. The light grey dots marked H and L show the high turnover and low turnover cases, respectively. The arrows show the changes after applying cytostatic (red) or cytotoxic (blue) medication with magnitude Δ = 0.2, which keeps the overall growth reduction constant. The net growth rate r (light blue lines) and stochastic extinction risk q = δ0/β0 (thin black lines) of each scenario is also shown.