Tumour growth dynamics

Tumour growth has been shown to approximate to the exponential in human cancers and, in general, the doubling times range from weeks to months. In contrast, the replicative processes at the cellular level, the cell cycle is completed within a time interval of a few tenths of hours in the majority of cell types. This discrepancy is due to cell loss within the tumour and a growth fraction of less than unity. In normal tissues a steady state renewal system operates, which contains the enormous proliferative potential and tumour growth is a manifestation of a breakdown of normal regulatory feedback mechanisms. Techniques are now available which can quantitate the rate constant for cell production in human tumours and these measurements are being used to design specific treatment for special tumours.