Evaluation of continuous labelling data by a practical mathematical method with application to a virus-induced sarcoma of the rat.

A simple mathematical function is established which renders the increase of the labelling index during continuous labelling of an exponentially growing tumor. By known values of proliferative fraction, mean cell cycle time and tumor doubling time, the mode and extent of cell loss is determined. Three models for different modes of cell loss are introduced: Model A for cell loss equally affecting proliferative and resting cells; Model B for cell loss predominantly affecting one of the two cell compartments; Model C for cell loss during mitosis. The range of validity of the model function is specified. Experimental data of a Polyoma virus-induced renal sarcoma of the rat provide an example of applicability of the theoretical model.