[Principles of drug therapy of malignant tumors: determinants of the efficacy of cytostatic agents].

Successful therapy with the anticancer cytostatic agents are remarkably dependent on the appropriate dosage and schedules of the treatment. To this end however it is highly important to have insights into the tumorbiological, pharmacokinetics, pharmacobiochemical and molecular-biological factors which underline the efficacy of the cytostatic agents. The present communication intend to provide a comprehensive survey for the medical doctors attending cancer patients concerning the mode of action of those anti tumour agents traditionally classified as alkylating agents, antimetabolites, topoisomerase inhibitors, and antimitotic agents. It will be emphasized that the currently available agents show no specific action on the malignant cells because they are inhibitors of cell proliferation and target certain molecular mechanism implicated in the cell cycle. The basis for the relatively selective antitumour action are rather different for the various cytostatic agents, nevertheless the differential activation and also the repair capacity in the tumour and in the normal organs offer an explanation for the agents acting directly or indirectly on DNA. Knowledge of the mode of action of the cytostatic agents offer not only a better understanding for their therapeutic failure but gives guidelines for those tumorbiological features which are necessary for their efficacy. In the last years substantial data have accumulated which indicate the possibility to improve the therapeutic action by modulating the pharmacokinetic or the pharmacobiochemical determinants of the antitumour drug action.