This book covers various aspects of radiation oncology, its principles and practice in the management of cancer types and sites in the human body. The book is in two volumes: Volume One is devoted to basic and technical aspects; Volume Two provides the clinical basis of modern radiation oncology. The chapters focus on an evidence-based multidisciplinary approach to cancer management covering the indications, contouring, treatment technique, outcomes, and toxicities related to radiotherapy for various cancer sites. It includes separate chapters on radiation biology, physics, and palliative care. Additionally, the book also addresses contemporary topics including artificial intelligence in radiation oncology, the role of protons/heavy ions, and the conduct of clinical trials in radiation oncology. The book is a relevant resource for busy radiation oncology physicians, practitioners, and trainees/residents/fellows seeking to utilize evidence in the literature to guide the management of radiation therapy patients. The book can be valuable for other disciplines such as surgical oncology, medical oncology, palliative medicine in cancer management including basic scientists working in both developed and developing countries.