The present invention relates to a composition for use in preventing migration of cancer cells in a subject known or suspected to suffer from cancer, the composition comprising at least one metal complex having the structure (I), formula (I), wherein M is a metal, preferably selected from the group consisting of copper, iron, manganese and zinc, X is Xa or Xb, wherein Xa is selected from the group consisting of O, S and -N(R1)-, wherein R1 is H or alkyl, and wherein Xb is a group forming a coordinate covalent bond to a second metal M', preferably a group O, S or -N(R1)-, wherein M' is preferably selected from the group consisting of copper, iron, manganese and zinc, and wherein M' and M may be the same or different and are preferably the same, Z1 and Z2, are independently of each other a, substituted or unsubstituted, -Aryl-O-, -Aryl-N- or heteroaryl group, Y is Ya or Yb, wherein Ya is selected from the group consisting of H, alkyl, -OH, -SH, halogen, and -NR3R4, wherein R3 and R4, are independently of each other selected from H and alkyl, preferably R3 and R4 are both H, and wherein Yb is a group forming a coordinate covalent bond to M or M', preferably Yb is a group O, S or -N(RYb1RYb2), wherein RYb1 and RYb1, are, independently of each other, H or alkyl, preferably H, and wherein n and m are integers, which are independently of each other, 0 or 1, Y2 is water or a halogen, and wherein Y3 is water or a halogen. The present invention further relates to a combined preparation comprising the aforesaid composition as well as to an in vitro method, for determining whether cancer cells are susceptible to immobilizing by the aforesaid compound.