The present invention relates to the use of a biocompatible nanoparticle or nanoparticle aggregate, in combination with an external non-oscillating magnetic field, wherein said nanoparticle comprises a) a core comprising magnetic material； b) a biocompatible shell surrounding the core, and, optionally, c) a labelling agent, wherein the outer diameter of the shell is less than about 100 nm, to prepare a composition, wherein the composition is deprived of any cell targeting means. The present invention further relates to the compositions thus obtained and to their uses in the field of human health, for the treatment of cancer, or in diagnostic (imaging for example), for the monitoring of tumor evolution.
