Cancer Treatment Chemotherapy Chemotherapy is treatment with powerful medicine that is most often given by mouth or by injection.Unlike radiation therapy or surgery, chemotherapy drugs can treat cancers that have spread throughout your body. Often a combination of chemotherapy agents is used instead of a single drug. Chemotherapy is given in cycles, with each cycle followed by a recovery period. Treatment schedules for chemotherapy vary, depending on the type and extent of your cancer, the type of chemotherapy you are receiving and how your body reacts to it.Chemotherapy can be used alone or in combination with other treatments, such as radiation therapy and/or surgery. It can significantly reduce the risk of cancer returning. The chances of cancer returning and the potential benefit of chemotherapy depend on the type of cancer and other individual factors. Not all chemotherapy regimens are the same, so side effects from chemotherapy are dependent upon the type of chemotherapy received. One common side effect for most chemotherapy treatments is fatigue.