The branch of medicine that involves the prevention, diagnosis and treatment of cancer is known as oncology. Medical oncology, surgical oncology and radiation oncology are the three main divisions of oncology. Medical oncology is a mode of treatment of cancer through hormonal therapy, targeted therapy, chemotherapy and immunotherapy. It is mostly used in conjunction with radiation oncology and surgical oncology. Hormonal therapy is a cancer treatment that reduces or blocks the amount of hormones in the body to slow or stop the growth of cancer that uses hormones to grow. In chemotherapy treatment, drugs are used to destroy the cancer cells. Targeted therapy treatment also involves the use of drugs. It focuses on restricting the spread of cancer to other organs. Immunotherapy treatment activates the immune cells to fight against the cancer cells. The aim of this book is to present researches that have transformed this discipline and aided its advancement. It presents the complex subject of medical oncology in the most comprehensible and easy to understand language. It is an essential guide for both academicians and those who wish to pursue this discipline further.