Association between trastuzumab treatment interruption and survival in HER2-positive metastatic breast cancer patients: a retrospective study

This retrospective study analyzed the effect of trastuzumab treatment interruption on overall survival (OS) and progression-free survival (PFS) within two years after diagnosis in women with HER2-positive metastatic breast cancer. Sociodemographic, clinicopathological, and therapeutic variables were collected from medical records of patients diagnosed between 2013 and 2017 at a comprehensive cancer care center in Brazil. Survival estimates were performed using the Kaplan-Meier method and the log-rank test. The Cox Regression model was used to estimate the risk of outcomes. The average OS was 20.2 months, and the PFS was 13.1 months. Interruption of trastuzumab treatment was associated with an increase in overall survival time compared with continued treatment (22.5 months; 95% CI: 21.8 - 23.3 vs. 17.7 months; 95% CI: 15.9 - 19.4; <i>P</i> = 0.001). The adjusted risk model revealed that continued trastuzumab therapy was independently associated with a 2.86-fold increased risk of mortality.