The effect of combined modality therapy on local control and survival

The systemic component of combined modality therapeutic programs has influenced both the selection of the approach to local control and survival in a number of tumor types. The more effective systemic therapy is against metastatic cancer by itself, the greater the impact on local control and survival. This observation is consistent with the invariable inverse relationship between curability and tumor cell number. For some common cancers, local control is good, but survival remains poor because of the inability to deal effectively with micrometastases. Improved systemic treatment is likely to have an impact on survival may shift local control measures, in some cases, to radiation therapy or lesser surgery without radiation therapy. There remains a substantial number of tumor types where both local control and survival is poor. In these tumors, improvement in local control by itself is not likely to improve survival because of the presence of micrometastases, but such improvements must occur before we can have a true evaluation of the systemic treatment of micrometastases in these tumors. The recent understanding that the metastatic process is under genetic control and the cloning of metastases genes offers a substantial opportunity to control this process and influence both local control and survival.