This study aims to evaluate the function of the left ventricle through STE in cancer patients both before and after chemotherapy with Anthracycline - containing agents. Furthermore, the study seeks to establish a correlation between the reduction (%) of strain and strain rate with variables such as age, BMI, and BSA. Methods: The research design employed a cross-sectional approach, along with longitudinal follow - up, involving 31 cancer patients aged 47.5 ± 12.8, all recommended for treatment with Anthracycline - containing agents at the Oncology Department of Hue University Hospital of Medicine and Pharmacy. Results: Following chemotherapy, over an average of 3 ± 1.75 cycles, the rate of cardiotoxicity diagnosed based on ASE/ EACVI criteria (2014) was 38.7% (n = 12). No statistically significant differences were observed in left ventricular dimensions, left atrial volume, or left ventricular function parameters (LVEF, FS) as measured using M - Mode (p > 0.05) before and after chemotherapy. However, parameters gauged through Speckle Tracking, including GLS, GLSR, GCS, GCSR, displayed a significant decrease (p < 0.001), preceding the decline in LVEF measured by the Simpson method. Notably, these parameters, particularly GLS, exhibited more pronounced reduction in the cardiotoxicity group, with the majority experiencing a decline of ≥ 10% from baseline. Furthermore, the group subjected to ≥ 3 cycles of chemotherapy demonstrated greater reduction than those who underwent only 1 - 2 cycles. Within the chemotherapy subgroup, those treated with Doxorubicin exhibited a more substantial decrease in strain indexes compared to the Epirubicin - treated subgroup. Importantly, no correlations were identified between the reduction (%) of strain and strain rate and variables such as age (< 65), BMI (< 25kg/m2), and BSA (< 2 m2). Conclusion: The rate of myocardial toxicity is 38.7%. After an average of 3 ± 1.75 cycles of chemotherapy, the reduction in deformation indices decreased significantly (p < 0.001) and decreased earlier than LVEF. There was no correlation between the (%) reduction in deformation indices with age (< 65), BMI (< 25kg/m2), and BSA (< 2 m2).