Growth retardation in normal and malignant tissues

A similiarity is found in the regression and regrowth curves of normal and malignant tissues after radiation treatments. The similarity implies that even in malignant tissues there is the practical, at least, limitation of tumor growth as in a normal organ, which is due to growth rate retardation. The retardation is considered to be the result from homologous inhibition of tumor cells. A tumor has its own growth rate which varies according to its total cell number and its environment. Approximately six months old skin metastases from breast carcinoma are still growing but are very close to the asymptote size which appears to be about 1000 cubic millimeters.