In HER2 disease stage IB + II + III 90.7% of HER2-positive breast cancer patients received adjuvant chemotherapy (HER2 stage IB + II + III versus HER2 stage IA: OR = 6.21, CI95% = 2.83-13.64, p < 0.0001). The gene discussed is ERBB2; the disease is breast carcinoma.