TNNI3 and breast cancer: In the present study, control group had a significant rise in hs-cTnI after 3 months and 6 months compared to its baseline, also a strong significant negative correlation was detected between LVEF and hs-cTnI in both groups, which agrees with several previous studies that reported that serum levels of TnI elevated in breast cancer patients underwent sequential therapy with doxorubicin and trastuzumab and were associated with increased risk for significant LVEF drop [11, 26, 27].