ERBB2 and skin disorder: Patients receiving dual HER2 blocking therapy had a significant increase in the incidence of grade 3/4 diarrhea (RR 8.22, 95% CI 3.89–17.38, p < 0.00001), hepatic toxicity (RR 2.32, 95% CI 1.30–4.14, p=0.004), skin disorder (RR 4.20, 95% CI 2.40–7.34, p < 0.00001), and nausea and vomiting (RR 3.51, 95% CI 1.19–10.38, p=0.02).