Effect and safety of dual anti-human epidermal growth factor receptor 2 therapy compared to monotherapy in patients with human epidermal growth factor receptor 2-positive breast cancer: a systematic review

Background: Dual anti-human epidermal growth factor receptor 2 (HER2) therapies have been shown to improve outcomes of HER2-positive breast cancer patients. We undertook a systematic review to compare treatment outcomes for patients who received single or combined anti-HER2 therapies. Methods: We identified randomized control trials that compared dual anti-HER2 therapy and anti-HER2 monotherapy in patients with HER2-positive breast cancer. Outcomes included pathologic complete response (pCR), overall survival (OS), progression-free survival (PFS), and adverse events. Included in the analysis were seven trials that recruited 2,609 patients. Results: In the neoadjuvant setting, the pooled pCR rate in the dual anti-HER2 therapy and monotherapy groups in combination with chemotherapy was 54.8% and 36%, respectively. This difference was statistically significant (relative risk, 1.56; 95% confidence interval (CI), 1.23-1.97; p < 0.001). In the metastatic setting, dual anti-HER2 therapy demonstrated significant benefits in both PFS (hazard ratio (HR), 0.71; 95% CI, 0.62-0.81; p < 0.001) and OS (HR, 0.68; 95% CI, 0.57-0.82; p < 0.001). Subgroup analyses indicated that the addition of chemotherapy to dual anti-HER2 therapy could greatly improve pCR in the neoadjuvant settings. However, in the metastatic setting, similar PFS and OS were found in patients receiving dual anti-HER2 therapy with or without chemotherapy. Dual anti-HER2 therapy was associated with more frequent adverse events than monotherapy, but no statistical differences were observed in cardiac toxicity. Conclusions: This systematic review provides a summary of all the data currently available, and confirms the benefits and risks of dual anti-HER2 therapy for HER2-positive breast cancer.