Studies of cellular proliferation in human leukemia. VIII. The generation time and growth fraction in lymphosarcoma in a leukemic phase during advanced and early relapsing disease.

The kinetics of cell proliferation were studied in a patient with lymphosarcoma in a leukemic phase both before treatment when the disease was very advanced and again at the earliest sign of bone marrow relapse following a drug-induced remission. During advanced disease, the pulse 3H-TdR labeling index (LI) was 11%, the mitotic index (MI) was 0.4% the growth fraction (GF) was 0.6, and the generation time (TG), as measured by the median grain count halving time, was estimated to be 160 hours. The patient went into remission for 25 days after a short course of therapy with prednisolone and arabinosylcytosine (Ara-C). During early relapsing disease, the LI was 17%; MI, 1.1%; GF, 1.0; and TG, 85 hours. The results of this study suggest that the rate of cell proliferation slows in leukemia as the tumor mass increases in volume, and that the slower growth is due to an increase in cell generation time, a decrease in the growth fraction, and an increased rate of spontaneous cell loss.