Figure 5.

Using the proposed extinction strategy, the second treatment is applied when the cancer population reaches no evidence of disease (NED) following first-line treatment. Note that the tumor is NED and thus the efficacy of treatment is not measurable. However, because the population is small and homogeneous, the second drug, although only marginally effective with elimination of 40% of the population, is nonetheless sufficient to drive the small homogeneous tumor to extinction. The histogram shows the phenotypic heterogeneity within the population before treatment (left) and just before the second strike (right).