Left Atrial Volume Index, Other Systolic and Diastolic Transthoracic Echocardiographic Parameters as Early Predictors for Asymptomatic Trastuzumab Target Cancer Therapy-Related Cardiac Dysfunction among HER2-Positive Breast Cancer Patients at a Tertiary Medical Center in Metro Manila – a Single-Center Prospective Cohort Study

Background: A quarter of breast cancer (BrCA) patients overexpress human epidermal growth factor receptors II (HER2); associated with aggressive tumor growth and adverse prognosis. Those undergoing cancer treatment with or without radiation therapy are at higher risk for developing cancer therapy-related cardiac dysfunction (CTRCD). Methods: This was a prospective cohort study with a computed sample size of 42 (margin of error set at 10% with confidence interval at 99%). The general objective was to determine the association of left atrial volume index (LAVI) with early asymptomatic CTRCD among HER2-positive BrCA patients receiving trastuzumab. Results: A total 45 patients were included in this study, 49% had LAVI > 27 ml/m 2 . More patients with LAVI > 27 ml/m 2 developed CTRCD. At baseline 2Decho, those who developed CTRCD had significantly higher median LV-GLS and median mitral EA ratio (all p < 0.05). On follow-up study, those with CTRCD had significantly lower median LV-GLS and median septal E (all p < 0.05). Consequently, those who developed CTRCD had significantly higher median relative reduction in LV-GLS and significantly higher decline in median mitral EA ratio (all p < 0.05). Asymptomatic CTRCD was significantly five times more likely among those stratified medium risk and higher [95% CI (1.109, 21.538)]. The odds of initiating cardioprotective strategy (CPS) before cancer therapy was significantly 70% less likely among those stratified low risk [95% CI (0.100, 0.998)], whereas the odds of initiating CPS during cancer therapy was significantly 15 times more likely among those stratified medium risk or higher [95% CI (1.622, 134.649)]. Adjusting for age and hypertension, the odds of developing asymptomatic CTRCD and initiating cardioprotective strategy during cancer therapy was significantly decreased by three per cent among those who have normal mitral EA ratio on baseline 2Decho [95% CI (0.952, 0.994) and 95% CI (0.957, 0.998), respectively]. Whereas initiating cardioprotective strategy before cancer therapy was significantly five per cent more likely when the mitral EA ratio was increased [95% CI (1.007, 1.063)]. Conclusion: In this small study of 45 randomly selected HER2-positive breast cancer patients, left atrial volume index was not associated with development of asymptomatic cardiotoxicity. Mitral EA ratio was significantly associated with development of asymptomatic trastuzumab target cancer therapy-related cardiac dysfunction and significantly influence the decision in initiating cardioprotective strategy prior to and during cancer therapy among cancer patients.