ABSTRACT
We now believe that, in many human cancers, the growing cells may be dividing quite rapidly, to produce new cancer cells every few days to weeks. However, the growth rates of most clinical cancers are often slower than the rate at which the individual cells comprising them are growing. Thus the clinical tumour may only double in size over weeks to months. This because many of the cells in a clinical cancer may not be dividing at all, and also because by no means all the new cells produced by cell division are able to survive or are capable of undergoing further divisions. It also has to be appreciated that individual cells, including cancer cells, are extremely small. One million cancer cells, for instance, would only be expected to occupy the same volume as the head of a pin.
