The title of this study is: A two-cohort, single-arm, exploratory Phase II clinical study on the primary/secondary prevention ADC drug of heltrombopag for thrombocytopenia caused by breast cancer. This study is a two-cohort, single-arm, open-label, exploratory clinical trial for the prevention of thrombocytopenia caused by ADC drug treatment for breast cancer. This research was supported by Fujian Cancer Hospital. The protocol has been reviewed by the Ethics Committee of Fujian Cancer Hospital, which has agreed to conduct this clinical study.