STEELS POTENTIAL DOUBLING TIME AND ITS ESTIMATION IN CELL-POPULATIONSAFFECTED BY NONUNIFORM CELL LOSS

The in vivo infusion of the thymidine analogue bromodeoxyuridine (BrdU rd), followed by delayed biopsy and bivariate DNA-BrdUrd flow cytometr y, makes it possible to estimate Steel's potential doubling time (T-po t) of human tumors. In the present paper, the expression of Steel's T- pot for a rather general cell population model, in which the distribut ion of cell loss is assumed to be nonuniform, is derived in terms of t he model parameters. We show that Steel's T-pot of a population can be markedly different from the doubling time that would be exhibited by the population in the absence of cell loss. These doubling times, on t he contrary, are equal when loss is uniform. Moreover, we studied the influence of modes of cell loss different from the uniform random loss on the estimation of T-pot by using the labeling index or the nu-func tion, quantities that can be determined from the bivariate DNA-BrdUrd distribution. (C) Elsevier Science Inc., 1997.