ERBB2 and breast cancer: Patients with HER2-positive breast cancer who received adjuvant chemotherapy within groups 2,3,4 had an inferior OS compared to Group 1 (HR 1.48, 95% CI 1.22-1.79, p<0.0001, HR 1.48, 95% CI 0.76-2.88, p-value = 0.25, and HR 1.05, 95% CI 0.39-2.84, p-value= 0.9162 respectively).