  In this paper we propose an ecological resilience point of view on cancer.
This view is based on the analysis of a simple ODE model for the interactions
between cancer and normal cells. The model presents two regimes for tumor
growth. In the first, cancer arises due to three reasons: a partial corruption
of the functions that avoid the growth of mutated cells, an aggressive
phenotype of tumor cells and exposure to external carcinogenic factors. In this
case, treatments may be effective if they drive the system to the basin of
attraction of the cancer cure state. In the second regime, cancer arises
because the repair system is intrinsically corrupted. In this case, the
complete cure is not possible since the cancer cure state is no more stable,
but tumor recurrence may be delayed if treatment is prolongued. We review three
indicators of the resilience of a stable equilibrium, related with size and
shape of its basin of attraction: latitude, precariousness and resistance. A
novel method to calculate these indicators is proposed. This method is simpler
and more efficient than those currently used, and may be easily applied to
other population dynamics models. We apply this method to the model and
investigate how these indicators behave with parameters changes. Finally, we
present some simulations to illustrate how the resilience analysis can be
applied to validated models in order to obtain indicators for personalized
cancer treatments.
  Keywords: Tumor growth; Chemotherapy; Basins of Attraction; Regime shifts;
Critical transitions
