Based on these assumptions, it is possible to resume some critical points, which are fundamental to understand the immunogenic effect caused (also) by radiation therapy: (A) The presence of tumor antigens (initiation of disease) is retained in memory by T and B lymphocytes; (B) Progression and the formation of metastases are caused by the immune system escaping the tumor; (C) The tumor’s microenvironment and the area ‘around’ GTV contains T lymphocytes (cytotoxic CD8, CD4 Helper, and FOXP3 regulators) activating or inhibiting the immune system [19]. The gene discussed is FOXP3; the disease is neoplasm.