Abstract. In the clinical cancer therapy regional hyperthermia certain nonlinear perfusion effects inside and outside the tumor seem to play a significant role. A stationary model of such effects leads to a nonlinear Helmholtz term within an elliptic boundary value problem. The present paper reports about the application of a recently designed adaptive multilevel FEM (code NEWTON-KASKADE) to this problem. For two 3D virtual patients, nonlinear and linear models are compared. Moreover, the numerical efficiency of the new algorithm is compared with a former application of an adaptive FEM to the corresponding non stationary model PDE.