Belmonte Beitia, Juan. Álvarez-Arenas Alcami, Arturo. García Otero, José . 

Celyvir viro-immunotherapy - a therapy using mesenchymal stem cells (MSCs) infected with the oncolytic adenovirus ICOVIR 5, an innovative oncolytic adenovirus - is a new therapeutic approach in cancer treatment. The purpose of this study is to create a mathematical model describing the relationships between immune, cancer and viral cells in pediatric patients with neuroblastoma. This was done by studying two different ways of applying the treatment: continuous and periodic therapy. Analysis of the first mathematical model identifies equilibrium points, their stability properties and bifurcation points. It can also identify bistability regimes in which therapy can induce either tumour-free equilibrium or tumour progression, depending only on the initial conditions. The second model reveals the existence of a threshold value of viral load, beyond which the patient’s recovery could be assured. The models make it clear that both the intensity of the viral load and the time over which treatment is given must be sufficient to ensure the success of the therapy. Low levels of treatment may fail to eliminate neuroblastoma, while stopping therapy early could lead to recurrence.