Moreover, a favorable pathological response, defined as a residual cancer burden (RCB) classification of 0 or 1, was observed more frequently among HER2-negative cases, with a prevalence of 54.5%, compared to 25% in HER2-low tumors (Chi-square = 4.425, df = 1, p = 0.035, Effect size phi = 0.3, Observed power = 0.627; Fisher’s exact test, p = 0.048). This evidence concerns the gene ERBB2 and cancer.