Contribution of in vivo proliferation/differentiation studies toward the development of a combined functional and morphologic system of classification of neoplastic diseases.

Proliferation kinetics of both leukemia and a variety of solid tumors have been assessed after in vivo infusions of the thymidine analogues, iododeoxyuridine (IUdR) and bromodeoxyuridine (BrdU). In acute myeloid leukemia (AML), these data indicate that the pretherapy cell cycle time (Tc) of myeloblasts is a prognostic indicator for remission duration since patients with slowly cycling myeloblasts had more durable remissions. The presence of in vivo differentiation detected from the day 7 biopsy after chemotherapy was also of favorable prognosis as these individuals had statistically significant improvement in their remission duration. The data in solid tumors are not mature enough for determining their clinical significance. Since cell kinetic information is readily available in a prompt fashion using these novel techniques, data can be used to plan therapeutic strategies for patients. This review discusses the state-of-the-art techniques available for cell cycle kinetic studies and the clinical and prognostic utility of data that have been generated thus far.