Problems in the Treatment of Slow-Growing Tumors

Abstract

The various aspects of the kinetics of slow-growing tumors in man are important in relation to the possibility of synchronization. Volume growth of many human tumors is slow compared to the tumors that grow so rapidly in small rodents. Three factors can be involved in this slow growth, and most often a combination of these factors is present. One is the prolongation of cell-cycle time, the second is the increasing fraction of cells that are not in cycle and which are not participating in the proliferation (Q-cells), and the third factor in some tumors is a significant degree of cell death. Cell death can be caused by different mechanisms; in some cells it may be due to an inherent deficiency which is incompatible with life, or it may be related to the structural environment of the tumor cells. The latter is probably the more frequent cause, and this cell death seems to be based on crowding and poor nutrition of the cells and is a direct or indirect consequence of overproduction of cells.

Some of the studies reported here were carried out in the program of the EORTC Screening and Pharmacology Group.