A 78-year-old woman with HER2-negative, hormone receptor-positive invasive ductal carcinoma of the breast undergoes a modified radical mastectomy and is referred for adjuvant chemotherapy, including doxorubicin and cyclophosphamide followed by paclitaxel. Baseline assessments, including CBC, renal function, and LFTs, are normal. Which of the following side effects is most strongly associated with cumulative doses of doxorubicin?