Comparison of pathologic complete response, disease-free survival, and overall survival results of patients with HER2 positive breast cancer who received neoadjuvant chemotherapy + trastuzumab and chemotherapy + trastuzumab + pertuzumab

Objective: Breast cancer is the most common cancer in women and ranks second among cancer-related deaths. In recent years, developing new therapeutic modalities for treating breast cancer has reduced breast cancer-related mortality rates. Neoadjuvant chemotherapy (NACT) is the standard treatment for locally advanced breast cancer. Achieving a pathologic complete response (pCR) to NACT has become increasingly important. Various clinical and pathologic markers have been investigated to predict this condition. In HER2-positive patients, adding anti-HER2 treatments to chemotherapy has improved oncologic outcomes. In particular, adding pertuzumab has been shown to increase pCR. In this study, we aimed to compare the pCR, disease-free survival (DFS), and overall survival (OS) outcomes of patients with HER2-positive breast cancer who received NACT+trastuzumab and chemotherapy+trastuzumab+pertuzumab and to evaluate the factors predicting pCR. Materials-Methods: The study included 102 patients admitted to the Meram Faculty of Medicine Hospital Medical Oncology Clinic between 2011 and 2023 who received neoadjuvant treatment for HER2-positive breast cancer and underwent post-treatment operation. The clinical, demographic, and pathologic characteristics obtained from the patient's medical records were retrospectively analyzed. Patients were grouped as NACT regimen plus trastuzumab alone and trastuzumab+pertuzumab according to their neoadjuvant treatment. The pCR, DFS, OS, and factors affecting pCR between the two groups were evaluated by statistical analysis. In addition, DFS and OS were compared according to the pCR status achieved in all patients receiving NACT+anti-HER2 treatment. Survival analyses were obtained using the Kaplan-Meier method. Results: The mean age of the 102 patients included in the study was 50.43 years (27-74), all female. 40.2% of the patients were postmenopausal, 59.8% were in stage 3, and 91.2% were in the locally advanced stage. The pCR rate was 41.2% in the whole group, 39.5% in the group that added trastuzumab alone to neoadjuvant chemotherapy, and 42.4% in the group that added trastuzumab+pertuzumab. Hormone receptor (HR) negativity, molecular type ER-PR-HER2+, and clinical N stage 0-1 were predictors of pCR. The 3-year OS rate was 92.2% and 97.7% in these two groups. Median DFS was 90.3 months in those receiving NACT+trastuzumab, while the median had yet to be reached in those receiving NACT+trastuzumab+pertuzumab. Furthermore, when all patients with and without pCR with NACT+anti-HER2 treatment were compared, OS was increased in those with pCR compared to those without pCR, although not significantly (92.6 months vs 80.5 months, p=0.41). Conclusion: Adding pertuzumab to NACT+trastuzumab in HER2-positive breast cancer increases pCR, DFS, and OS. HR negativity and clinical N stage 0-1 are independent predictors of pCR. With these clinical and pathologic properties, pCR can be predicted, and prognosis can be improved by increasing DFS and OS rates. Keywords: Breast cancer, neoadjuvant chemotherapy, pertuzumab, pathologic complete response, survival