Cell proliferation kinetics in five human solid tumors

The in‐vivo study of the cell cycle in human tumors with the labeled mitosis curve is possible if the choice of patient conforms to certain criteria. In four of our cases good data were obtained, T8 varied between 7 and 19 hours and Tc between 1 day and 4 days. In two of the patients the shape of the curve suggests large fluctuations of the durations of the various phases of the cell cycle. For the third patient the peak of the labeled mitosis curve never exceeds 50%; this large spread of the duration of the phases of the cell cycle within the tumor cell population may be due to previous treatment of his tumor. There is a large discrepancy between the clinical doubling time and the potential doubling time computed on the basis of Tc and GF and assuming no cell loss. This discrepancy seems to indicate that the extent of cell loss is a major parameter of the growth rate of human tumors.