The prognostication of a number of oncology patients and an evaluation of the resources' needs for the oncology service are in the focus of attention. A systemic dynamic model, based on a differential equations' system, is suggested to cope with the changing status of oncology patients. There is an example of using the model to forecast the number of patients with breast cancer for further calculation of resources needed by the palliative care service to render assistance to such patients and to evaluate the influence of preventive measures produced on the needs in resources by the mentioned service.