“…Third, all else being equal, the larger the subpopulation of sensitive cells, the lower the growth-rate of resistant cells (g r is non-increasing in S). This is a standard assumption in the adaptive therapy literature (see Supplementary Information, Section 1), which might result from density-dependence (the larger the tumour, the larger its doubling time [13,14,26], as in the Gompertzian Model 3), frequency-dependence (the rarer resistant cells, the larger their doubling time [8,9]), a combination of those two factors [4,8,15,17,18,21], or some other form of inhibition of resistant cells by sensitive cells. It is important to note that this assumption does not imply a fitness cost of resistance; we permit the possibility that resistant cells are as fit or even fitter than sensitive cells in the absence of treatment.…”