COMPARISON OF RESPONSE TO TREATMENT IN LINES SUBSEQUENT TO T-DM1 IN PATIENTS WITH METASTATIC HER2 POSITIVE BREAST CANCERS (Atena Editora)

Abstract

Introduction: Breast cancer has a strong epidemiological impact. Approximately 20% of them are HER-2 positive. In the metastatic setting, first-line treatment with pertuzumab, trastuzumab and taxane is consolidated by the CLEOPATRA study and second-line treatment, until recently, with trastuzumab-emtansine (T-DM1) by the EMILIA study. Sequencing after using T-DM1 lacks consistent information. Objectives: the primary outcome was the comparison of the response rate of patients undergoing subsequent line to T-DM1, in HER2-positive metastatic breast cancer. Secondary objectives were to compare Overall Survival (OS), Progression-Free Survival to T-DM1 (PFS), Progression-Free Survival to subsequent line (PFS2), Time to Treatment Failure (TFT) and adverse events. Methods: Retrospective, single-center study, including 67 patients with HER2-positive metastatic breast cancer exposed to T-DM1 between August 2013 and December 2021. Of the 67 patients, 38 received subsequent lines of treatment, with a median follow-up of 34 months. Treatments subsequent to T-DM1 were divided into 3 groups: Group 1 = capecitabine + lapatinib (21 patients); Group 2 = trastuzumab-deruxtecan (5 patients) and Group 3 = anti-HER2 associated with chemotherapy (12 patients). Results: The response rate was 19% in group 1, 60% in group 2 and patients in group 3 showed disease stability. The DFS was 15 months. The median OS of T-DM1 was 47 months. No patient in Group 2 experienced progression or death. There was no significant difference in PFS between groups 1 and 3. Conclusion: The response rate varied according to the subsequent line, being favorable to trastuzumab-deruxtecan, which also had lower toxicity. Comparison of OS between groups was not possible due to the number of patients included and events.