Efficacy of Trastuzumab Emtansine Therapy in Sequantial Treatment in Patients with HER2-Positive Metastatic Breast Cancer

Aim: The aim of this study was to evaluate the efficacy of Lapatinib, trastuzumab emtansine (T-DM1) treatment after pertuzumab in patients with HER2-positive metastatic breast cancer.

Materials and Methods: The study included HER2-positive breast cancer patients who were followed up and treated in Adana City Training and Research Hospital. Totally 1840 patients with a diagnosis of breast cancer in the hospital management system were evaluated, 670 patients who were determined to be metastatic were evaluated for eligibility. Thirty-one patients who received pertuzumab before T-DM1 treatment, while 34 patients who received T-DM1 before pertuzumab were included.

Results: Of the 65 female patients included in the study, 59 had ductal adenocarcinoma (90.8%) and 6 had lobular adenocarcinoma (9.2%). Seventeen patients (26.2%) had bone metastases, 20 patients (30.7%) had visceral metastases, and 28 patients (43.1%) had bone and visceral metastases together. Overall survival (OS) was 23.8±3 months in those who did not receive pertuzumab before T-DM1 in the metastatic setting, while it was similar in those who received pertuzumab with 22.4±2.9 months (p=0.969). Progression-free survival (PFS) was 9.1±1.3 months in those who did not receive pertuzumab before T-DM1 in the metastatic setting, while it was significantly lower in patients who received pertuzumab with 4.9±0.8 months (p=0.005). The comparison of initiation of T-DM1 after pertuzumab as second-line therapy in the metastatic setting and its use in later therapeutic lines revealed no difference in PFS and OS (p=0.628 and p=0.706, respectively).

Conclusion: Pertuzumab should be preferred primarily because it is more effective in metastatic HER2-positive breast cancer. Despite the significant decrease in PFS of patients using T-DM1 after pertuzumab, there was no decrease in OS; therefore the earlier T-DM1 therapy is initiated following pertuzumab, the more effective it is.