The Korean Breast Cancer Society revised the treatment recommendation on the 27th. Combination drug treatment using a combination of an antibody and an anticancer drug has emerged as a hot issue, and as the new anticancer drug Enhertu for HER2-positive metastatic breast cancer received domestic approval in September last year, the reflection of this is emerging as a concern. In the case of new drugs, society reflects them if there is evidence, while also preparing new recommendations for rare cases that have been neglected. It means that it presented an 'answer' based on expert consensus in areas where large-scale randomized clinical studies were lacking due to the small number of patients, such as male breast cancer, os