The present invention relates to a system comprising (1) an medical device comprising injectable magnetizable nanoparticles and means for injecting the same, and (2) means for applying a constraint to a tumor associated to an neoangiogenic network where, after having been injected, the particles are retained the present invention also relates to a method for treating tumors, especially tumors associated with a neoangiogenic network, comprising the steps of:- injecting a composition comprising magnetizable nanoparticles- optionally performing imaging using an imaging device to detect a concentration of nanoparticles retained in the neoangiogenic network and- applying a means for applying a contact-free constraint onto a tumor in vivo, said means being a gradient of magnetic field and the application being directed to the tumor region.
