Cell Kinetics and Cancer Therapy

It is a well-established fact that the cytotoxicity of radiation and of most anticancer drugs depends on cell kinetic parameters (Sinclair 1967, Mendelsohn 1975, Valeriote and v. Putten 1975, Bhuyan 1977). This has suggested the idea of exploiting kinetic differences between neoplastic and sensitive normal tissues in order to achieve selective cell kill, i. e. killing a great fraction of tumor cells while sparing the normal cells of the renewal tissues (bone marrow, epithelium of the small intestine, skin). Indeed, cell kinetics are a corner-stone of many theoretical concepts in the treatment of cancer by radiation or cytotoxic drugs (Frei et al. 1969, Skipper and Perry 1970, Skipper 1971, Clarkson 1974, Klein and Lennartz 1974, Southwest Oncology Group 1974, Withers 1975, Valeriote and Edelstein 1977, Gerecke 1979, Swan 1980, Smets 1983). Some attempts to design therapy schedules on a rational basis with cell kinetic concepts have failed in practice and consequently the optimism of the period about 1970 has been displaced by skepticism (v. Putten, 1974) about the benefit of cell kinetics for therapy. But recently this approach has become favored again. There has been a careful palpating of the possibilities and limits of cytokinetic theory in clinical practice (Langen 1980) and the conviction that early failures should be attributed to the lack of data rather than to a presumed inconsistency of cell kinetic theory (Pallavicini et al. 1982).