Welcome to the 4th edition of this handbook. Over the previous editions, we have tried to evolve the content and style to make the book more accessible and useful to our readers. This has continued in edition four with alterations, in response to reader feedback and as a result of new data emerging in many cancer fields. Oncology has continued to produce novel diagnostics, treatment strategies, and drugs which benefit patients. The so-called ‘standard of care’ is a moving target, and significant differences do exist across nations. As far as possible, we have tried to indicate these controversies and invite the reader to explore them through suggested reading lists. The book is not a comprehensive textbook but serve as a primer and base, on which to build more detailed understanding of the disease and its management. This is our fourth attempt to perfect the handbook. It will never be perfect—thankfully, oncology practice moves so quickly we will always be chasing. However, we have individually and collectively made extensive updates to the content. We hope that it is adequately broad, and yet detailed enough, to serve its purpose.