Abstract PS7-79: Clinicopathological characteristics of male breast cancer in Japan from the national clinical database
Authors: Akihiko Shimomura, Masayuki Nagahashi, Hiraku Kumamaru, Yutaka Yamamoto, Hiromitsu Jinno, Shigeru Imoto
Journal: Cancer Research (2021)

Abstract Background: Male breast cancer is a rare cancer. According to the Japanese Breast Cancer Society's Breast Cancer Registry, there were 613 cases of male breast cancer in 2016. It is only 0.6% of all cases of breast cancer incidence. Because of its rarity, there have been no comprehensive studies on characteristics of male breast cancer in Japan. Therefore, there has been few specific treatments developed for male breast cancer. In this study, we investigated the prevalence and clinicopathological characteristics of male breast cancer in Japan, using the most reliable domestic data, the National Clinical Database (NCD). NCD is a database that collects medical information on diseases, treatments, and surgeries in Japan. In collaboration and cooperation with academic societies and academic organizations, NCD maintain and manage the collected data. The data are used in domestic research to evaluate the standards of medical care and support clinical research. This study conducted with a collaboration with NCD and the registration committee of Japan Breast Cancer Society. Materials and Methods: Clinicopathological data were collected from all breast cancer patients in NCD between 2012 and 2018. We compared the male and female breast cancer patients on age, stage, surgical technique, estrogen receptor (ER) status, progesterone receptor (PgR) status, HER2 expression, family history, comorbidities, and systemic treatment history. Results: 3,780 male and 590,636 female breast cancers were enrolled in the study. The median age was 71 years for men (56-87 years, 5-95 percentile) and 61 years for women (40-83 years). The clinical stage in males was 7.2% in stage 0, 36.3% in stage I, 33.4% in stage II, 12.4% in stage III, 1.4% in Stage IV and 4.5% in unknown, respectively. In females, 13.0%, 41.6%, 31.4%, 6.6%, 1.3% and 2.3%, respectively. Breast conserving surgery (BCS) was performed for 14.6% in men 46.2% in women. BCS rate in men is more frequent in Japan compared to in western countries (Ann Oncol. 2018 Feb 1;29(2):405-417). Hormone receptor-positive (HR+; ER+ and/or PgR+) HER2-negative (HER2-) was 88%, HR+HER2-positive (HER2+) was 8%, HR-HER2+ was 1% and HR-HER2- was 3% in men. 74%, 10%, 6% and 10% in women, respectively. The distribution of subtypes in men is similar to western countries. Comorbidity was reported in 42.3% of men and 66.8% of women. Hypertension, diabetes, cardiac disorder and cerebrovascular disorder were more common in men. Conclusion: Male breast cancer is 0.6% of all breast cancer in Japan. Stage III and HR+ is more frequent in male and its tendency is similar to data from western countries. BCS is underwent more frequent in Japan than in western countries. Citation Format: Akihiko Shimomura, Masayuki Nagahashi, Hiraku Kumamaru, Yutaka Yamamoto, Hiromitsu Jinno, Shigeru Imoto, Registration Committee of Japan Breast Cancer Society. Clinicopathological characteristics of male breast cancer in Japan from the national clinical database [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-79.