Oncology is a branch of science that examines the formation, causes, diagnosis, treatment and relationship of tumors in the body with heredity. It examines non-cancerous cells as well as cancerous cells. This broadens the fields of interest in oncology. Medical oncology, which examines chemotherapy applications which means treatment of cancer with medication, also examines cancer prevention, cancer screening and early diagnosis applications. Radiation oncology is a medical science that studies the effects of treatment procedures using radiotherapy on cancer cells. Cancer surgeries are often performed by oncological surgeons with advanced expertise in the surgery of the respective cancer.