RESUMO
The relationship between host immune response and tumor cells is currently defined by the immunoediting concept, including three phases: elimination, equilibrium and escape. Cancer cells are initially eliminated by the immune system, but progressively can develop escape mechanisms. The balance between elimination and escape depends on the prevailing activity of cytotoxic Th1 or immunosuppressive Th2 lymphocytes. Surgery has the potential to eradicate the disease, but, along with other perioperative circumstances, can induce a variable degree and period of immunosuppression. By modifying the Th1/Th2 ratio, these perioperative circumstances may favor the escaping mechanisms and, consequently, promote cancer recurrence and metastasis altering long term prognosis of cancer patients.