A solid therapeutic agent for use in a method of treating a tumor comprising: implanting an implantable drug delivery device into the tumor, the device formed from at least one wire (70) having holes (72) with the solid therapeutic agent provided in the holes; and delivering the therapeutic agent to the tumor from the holes (72).A drug delivery device, which is a wire (70), has through holes in it (72), the through holes (72) are filled with a solid agent, and the solid-agent-filled through holes (72) are provided in multiple directions in the wire (70)