Contrasting the impact of cytotoxic and cytostatic drug therapies on tumour progression
Ratios of expected waiting times until progression of cytostatic (red, target β0) and cytotoxic (blue, target δ0) compared to no therapy, under different migration μ and driver mutation rates γ from Eqs 2–6; black this line denotes equally long waiting times (i.e the ratio = 1). High turnover cases have (β0 = 1.0, δ0 = 0.6) and low turnover cases (β0 = 0.42, δ0 = 0.02), treatment strength Δ = 0.2. A,B High and low turnover cases where cell competition at the primary tumour is due to increasing death rates. Both treatments are better than no treatment, and cytotoxic (blue) is superior to cytostatic (red) treatment. C High turnover case where cell competition at the primary tumour is due to decreasing birth rates. Both treatments are better than no treatment and cytostatic treatment is better than cytotoxic when μ/γ < (β0 − δ0 − Δ). D Low turnover case where cell competition at the primary tumour is due to decreasing birth rates. Cytotoxic treatment is better than cytostatic treatment when μ/γ > (β0 − δ0 − Δ) and better than no treatment if μ/γ > (β0 − 2 δ0 − Δ). Cytostatic treatment is always better than no treatment. For each case, at least one of the treatments is better than no therapy.