Masakazu Toi1, Jin Ye Yeo2
1Tokyo Metropolitan Komagome Hospital (Tokyo Metropolitan Cancer and Infectious Disease Center), Tokyo, Japan; 2ABS Editorial Office, AME Publishing Company
Correspondence to: Jin Ye Yeo. ABS Editorial Office, AME Publishing Company. Email: abs@amegroups.com
This interview can be cited as: Toi M, Yeo JY. Meeting the Editorial Board Member of ABS: Dr. Masakazu Toi. Ann Breast Surg. 2025. Available from: https://abs.amegroups.org/post/view/meeting-the-editorial-board-member-of-abs-dr-masakazu-toi.
Expert introduction
Dr. Masakazu Toi (Figure 1) graduated in 1982 from Hiroshima University School of Medicine with his Medical Doctorate and in 1988 with his Ph.D. Dr. Toi studied molecular biology, particularly hormone resistance and tumor angiogenesis, at the Institute of Molecular Medicine of Oxford University, UK, from 1990 to 1992. He was appointed to the Department of Clinical Oncology, John-Radcliffe Hospital of Oxford University, as an academic visitor (Prof. Adrian L Harris). From 1992 to 2007, Dr. Toi worked for the Tokyo Metropolitan Cancer and Infectious Disease Center, a high-volume center of the Tokyo Metropolitan Government, Japan. He was appointed as a director of Surgery and a director of Clinical Trial Department. In 2000, he studied at the Department of Breast Medical Oncology, Dana-Farber Cancer Institute of Harvard University as a Yamagiwa-Yoshida fellow, UICC (Prof. Eric Winer). Since 2007, Dr. Toi has been appointed as Professor of Breast Surgery at the Graduate School of Medicine, Kyoto University, Japan, and Director of the Breast Cancer Team, Kyoto University Hospital. He was appointed as the Deputy Director of the Society-Academia Collaboration for Innovation of Kyoto University from 2016 to 2018. He was appointed as the Director of Tokyo Metropolitan Komagome Hospital in April 2023.
Dr. Toi has been involved many clinical trials of new therapy development and new diagnostics development especially for breast cancer. He contributed to over 800 original papers, reviews, and books. His current interests in laboratories are breast cancer tumor-immune microenvironment (TIME), molecular imaging of the TIME, association between genomics and TIME and the significance of TIME in treatment, screening and prevention.
Figure 1 Dr. Masakazu Toi
Interview
ABS: Your research focuses on breast cancer, specifically the tumor-immune microenvironment (TIME). What first sparked your interest in this area?
Dr. Toi: In 1990-1992, I studied angiogenesis in the UK. During that time, I discovered that IL-4 promotes the proliferation of vascular endothelial cells. IL-4 is a cytokine originally identified by Professor Tasuku Honjo as an immune regulator. Under the supervision of Professor Adrian Harris, I found that IL-4 also promotes the proliferation of breast cancer cells. This discovery motivated me to continue researching the tumor microenvironment. I dedicated myself to analyzing the expression and abnormalities of various molecules expressed in the TIME using human breast cancer tissue. Although it was not well understood at the time, I was the first to report that we could distinguish between protumor and antitumor macrophages with CD68 and thymidine phosphorylase (TP) as indicators. This approach was also useful for identifying the dynamics of TIME. Since then, I have focused on the changes of TIME and its modifications caused by treatments.
ABS: Could you elaborate on the publications on the molecular imaging of the TIME? What are some of the most promising findings that stood out to you, and how do they potentially impact treatment outcomes for patients with breast cancer?
Dr. Toi: While studying angiogenesis, I began to think it would be beneficial to diagnose and image cancer by focusing on tumor angiogenesis. In 2007, I became a professor at the Kyoto University School of Medicine, where the development of photo-acoustic imaging (PAI) technology was just beginning. I joined a group within the Canon-Kyoto University project and was involved in developing PAI equipment for breast and lymphatic vessels. Subsequently, I participated in the ImPACT project of the Japanese Cabinet Office.
ABS: With over 800 publications in the field, you have made significant contributions to breast cancer treatment, diagnostics, and prevention. What do you consider to be your most important or groundbreaking findings to date?
Dr. Toi: In breast cancer diagnosis, I have researched the PAI equipment mentioned above. Regarding treatment, we created a clinical trial system concentrating on residual invasive cancer after preoperative systemic therapy, which has received international recognition. We conducted a clinical trial to determine whether oral fluoropyrimidine should be added after surgery for patients with invasive residual disease after neoadjuvant chemotherapy, proving its additional efficacy. This clinical trial system subsequently contributed to the development of CDK4/6 inhibitors, PARP inhibitors, and other medications that yielded significant results. It is now established as a test system widely used as a platform for developing new drugs, and it is also applied to clinical trials for other cancers beyond breast cancer. Furthermore, we can consider the preoperative and postoperative treatment sequence as a unified treatment system, improving cases that are refractory, resistant, or have a poor prognosis while developing a new treatment strategy aimed at therapy escalation in that patient group. Thus, we can say that we have laid the groundwork for developing a therapy escalation strategy.
ABS: In your opinion, what are the biggest challenges in studying the TIME, especially in the context of breast cancer, and how do you overcome these challenges in your research?
Dr. Toi: TIME is the site of tumor formation and where the effects of various treatments—including immunotherapy, anti-HER2 therapy, targeted therapies, endocrine therapy, and chemotherapy—are expressed. It is here that it is determined whether the damaged cancer cells will achieve a complete response or remission, or remain in partial response. The involvement of immune cells is crucial in expressing the effects of these treatments. It is no exaggeration to say that immune cells act as the ultimate determinants. Therefore, the characteristics, state, changes, and dynamics of TIME can be seen as one of the key factors affecting cancer treatment outcomes. We consider elucidating its molecular mechanisms to be the biggest challenge, as it is essential for developing new treatments.
ABS: You have been involved in numerous clinical trials for new therapies. What recent developments in breast cancer treatment or diagnostics are you particularly excited about?
Dr. Toi: Historically, significant breakthroughs have been made through endocrine therapy, anti-HER2 therapy, CDK inhibitors, immune checkpoint inhibitors, and antibody-drug conjugates. Recently, new signal transduction inhibitors have also gained attention. In addition, new classes of drugs and improved versions of existing drugs that offer enhanced efficacy or reduced toxicity are continuously being developed. I am particularly interested in optimizing these treatments, developing combination therapies, and maximizing the balance of their advantages and disadvantages.
ABS: Looking ahead, how do you hope to continue impacting the field of breast cancer research?
Dr. Toi: I aspire to keep developing new treatments, treatment platforms, and new diagnostics. I also want to continue to develop artificial intelligence (AI)-driven medicine.
ABS: As an Editorial Board Member, what are your aspirations for ABS?
Dr. Toi: I hope that ABS will become even more effective in communicating information from Asia.