  We present a model for the interaction dynamics of lymphocytes-tumor cells
population. This model reproduces all known states for the tumor. Futherly,we
develop it taking into account periodical immunotheraphy treatment with
cytokines alone. A detailed analysis for the evolution of tumor cells as a
function of frecuency and theraphy burden applied for the periodical treatment
is carried out. Certain threshold values for the frecuency and applied doses
are derived from this analysis. So it seems possible to control and reduce the
growth of the tumor. Also, constant values for cytokines doses seems to be a
succesful treatment.
