Kinetic and mechanical aspects of metastasis

Progress in cancer treatment, while real, has been slow: most of the change in survival in recent decades has been from earlier detection, and only for a few specific cancers. What makes advanced cancers so difficult to treat is their ability to metastasise (to seed off new tumours elsewhere). This process requires cancer cells to become motile, but how exactly this affects cancer growth and the causes of the transition are unclear. Here we discuss a simple, generic model of the growth of an ensemble of malignant lesions which shows that even rare, local migration can dramatically alter the growth rate of the tumour. This may provide a clue as to why observed in vivo tumour growth rates vary so widely between different cancers and patients despite very similar division rates of individual cells. The model also suggests that slowing down migration (one target of experimental biotherapy) could significantly increase the survival time even without killing cancer cells.