Background: Although diastolic dysfunction is common among patients treated with cancer therapy, no clear evidence has been shown that it predicts systolic dysfunction. This study evaluated the correlation of longitudinal diastolic strain (Ds) with echocardiography diastolic parameters and to estimate its role in the early detection of cardiotoxicity among patients with active breast cancer. Methods: Data were collected as part of the Israel Cardio-Oncology Registry (ICOR), a prospective registry enrolling all adult patients referred to the cardio-oncology clinic. All patients with breast cancer, planned for Doxorubicin therapy were included. Echocardiography, including Global longitudinal systolic strain (GLS) and Ds, was assessed at baseline before chemotherapy (T1), during Doxorubicin therapy (T2) and after the completion of Doxorubicin therapy (T3). Cardiotoxicity were determined by GLS relative reduction of ≥15%. Ds was assessed as the time of lengthening =diastolic time (ms) measured. Results: Among 69 patients, 67 (97.1%) were females with a mean age 52±13years. Diastolic strain time measurement was significantly associated with the standard diastolic parameters. Significant GLS reduction was observed in 10 (20%) patients at T3 . Both in a univariate and a multivariate analyses the change in Ds basal time from T1 to T2 emerged to be significantly associated with GLS reduction at T3 (p<0.04). Conclusions: Among breast cancer patients, Ds time showed high correlation to standard diastolic echocardiography parameters. Relative reduction in Ds basal time emerged associated with clinically significant systolic dysfunction as measured by GLS reduction.