Cell population kinetics of human solid tumors: a statistical analysis in various histological types

Pooled individual data from the literature on human tumor cell kinetics were statistically analyzed. The thymidine labeling index was obtained for 693 solid tumors and the geometric mean values (LI) were calculated for all tumors combined and for tumors grouped into 10 histological types. Lymphoma, undifferentiated lung carcinoma, childhood carcinoma and squamous epithelioma showed significantly higher LI than all tumors combined. On the other hand, melanoma, adenocarcinoma, brain tumors and mesenchymal sarcoma showed lower LI than all tumors combined, and the values decreased in that order. The geometric mean of the growth fraction (GF) was significantly different among different histological types and was highly correlated with LI when log (GF/LI) was plotted against log LI. With limited data, the mean cell cycle times (Tc) of squamous epithelioma and adenocarcinoma did not appear to be different. The data on the cell loss factor (CL) were insufficient to permit comparison of the differences among histological types. However, the CL values were distributed within a narrow range from 78 to 99%. Thus, GF seems to vary among histological types, and this is reflected by the variation of LI.