When is chemotherapy used as a treatment?

In definitive therapy when the best chance of cure is with chemotherapy. In neo–adjuvant therapy prior to surgery or radiation to reduce tumour burden prior to definitive therapy with either modality. In combination therapy with radiotherapy, either sequentially or concurrently, to enhance the effects of radiation (chemo radiation). In secondary therapy to try to cure metastatic disease. In palliative therapy to improve specific symptoms and enhance the quality of life.