This book shares cutting-edge evidence on Hereditary Breast and Ovarian Cancer (HBOC) treatment, delivering facts on breast cancer, gynecologic oncology, and basic research to contribute to clinicians' practices. Each chapter presents the latest clinical techniques, basic experimental results, and the best-chosen research findings. The book is based on the works presented at the Japanese Organization of Hereditary Brest and Ovarian Cancer (JOHBOC) and a special chapter delivers a study based on the extensive data from the Japanese HBOC patients registered in the society's database, presenting novel evidence for further advancement in the field. The practice for HBOC has been rapidly increasing due to the clinical development of poly(ADP-ribose) polymerase inhibitors and the spread of companion diagnostics. In addition, the insurance coverage of a part of HBOC treatment raised social awareness in Japan, and the book illustrates not only clinical efforts but also issues related to the social system and the efforts of the association of related organizations.  Hereditary Breast and Ovarian Cancer - Annual meeting of JOHBOC will be of interest to breast surgeons, obstetricians and gynecologists, pancreatic cancer surgeons, and urologists engaged in HBOC treatment through the implementation of companion diagnostics for PARP inhibitors administration. Also, physicians occupied in genetic medicine who perform genetic testing and medical staff practicing HBOC will find this book insightful. It is also for HBOC patients and their families, medical administrators in the social system of HBOC practice. Editors and authors hope to contribute to the equalization and widespread of HBOC practice and serve as a foundation for future advances in the disease's treatment and medical practice.