Faced with limited resources and the desire to improve the quality of cancer care, there is an increasing interest among physicians in maximizing gains in cancer treatment. This paper discusses where to find cost-benefit estimates for a host of adverse events in cancer treatments. In order to clarify the relationship between the input resources and economic effects of supportive therapies against adverse events, we developed a system model, similar to the Marcov model, of prognosis of principal seven cancers and analyzed the balance of patient labor productivity (Benefit) and accumulated cancer care costs (Cost). Economic analysis is a useful guide to resource allocation and appropriate decision making for improving patient's QOL.