Radiation therapy or radiotherapy is the attempt to remedy a health problem by making use of ionizing radiation. Radiotherapy is generally applied to fight cancer because ionizing radiation is an effective cell killer. The primary objective of radiotherapy is to cause reproductive cell death, not functional cell death. It is often used as a primary therapy, but it can also be combined with surgery, chemotherapy, hormone therapy or some mixture of the three. The specific purpose of a treatment depends on the type of tumor, its location, its stage and the patient's general health. The application of radiotherapy to non-malignant diseases is limited by concerns about the risk of radiation-induced cancers.