ERBB2 and gastric cancer: As T-DXd was expected to have a clinical benefit for patients with previously treated HER2-positive advanced gastric cancer, it was granted Sakigake designation by the Japan Ministry of Health, Labour and Welfare (MHLW) on March 27, 2018, following the Breakthrough Therapy and Fast Track designation for HER2-positive metastatic breast cancer granted by the United States Food and Drug Administration; thus, T-DXd was considered to be a drug with high societal demand [22].