Background: Anthracycline-based chemotherapy is highly effective in breast cancer treatment but is limited by dose-dependent cardiotoxicity. Early identification of subclinical myocardial injury is crucial to prevent progression to irreversible dysfunction. Objectives: To evaluate whether a multimodal surveillance strategy integrating left ventricular global longitudinal strain (LVGLS), left atrial reservoir strain (LASr), and high-sensitivity troponin I (hs-TnI) can predict early anthracyclineinduced cardiotoxicity. Methods: This retrospective cohort study included 50 female breast cancer patients (mean age 49.3 ± 8.5 years) treated between January 2022 and December 2024. Echocardiography and biomarkers were assessed at baseline and 1 month after chemotherapy. Cardiotoxicity was defined as a > 10% reduction in LVEF to < 53%. Results: Cardiotoxicity occurred in 15 patients (30%). LVGLS, LASr, and hs-TnI significantly changed (all P < 0.001).Independent predictors were LVGLS (aOR 1.33), LASr (aOR 0.77), and hs-TnI (aOR 1.07). hs-TnI showed the highest discriminative ability (AUC 0.940). Conclusions LVGLS, LASr, and hs-TnI provide complementary information for early detection of cardiotoxicity.