“…Mathematical models of tumor growth and tumor-immune system interaction are derived by mainly using Ordinary Differential Equations (ODEs) (see, for example, [7], [14], [17], [20] and references therein), Delay Differantial Equations (DDEs) (see, for example, [2], [3], [4], [8], [9], [11], [21], [22] and references therein) and Partial Differential Equations (PDEs) (see, for example, [10] and references therein). One of ODE models was introduced by Kuznetsov and Taylor [16] which has the following form:…”