Background: A tumor system not only consists of diverse cell types but also comprises all components of action insofar that these components are oriented in terms of diverse cell types. Methods: Thus, it is necessary to decode paradox situations of cellular rationalization, deformation, and communication processes or, in other words, to uncover inconsistencies within tumor cell compartments or distinct topologies of aggregated action effects. Here, a theory may be helpful that discharges into an action-theoretical abstraction and simultaneously includes evolutionary tumor developments. In an evolutionary process, tumor cells may exploit the whole extent of the rationalization features of stroma cells to implement the functional diversity of systems behavior aimed at maintaining homeostasis, and robustness in tumor systems. The introduction of genomic/non-genomic systems-directed therapeutic approaches may allow both, the uncovering of systems topologies of aggregated action effects and the broadening of therapeutic options via systems-directed approaches. Results: (1) Tumor systems biology is now turning into a scientific co-subject. (2) Developing actiontheoretical systems terms with the corresponding conceptual equipment may contribute to the classification of tumor subsystems. (3) Systems-directed therapies may meet new therapeutic requirements, which might help to create therapeutic approaches that are specifically designed for the demand of tumor stages, corresponding systems stages. Conclusions: Therefore, patients would probably not have to be selected according to age and/or co-morbidities because of known adverse toxicities of standard therapies (maximal tolerable doses). In contrast, therapies may meet the (individual) tumor system's characteristics by a systems-orientated selection of biomodulatory acting agents. As shown, toxicities may be modest.