Winning the battle, but losing the war: mechanisms and morphology of cancer-therapy-associated cardiovascular toxicity

In the United States, the lifetime risk of a cancer diagnosis is nearly 40%; in 2016, that represents almost 1.6 million new patients, and despite advances in early diagnosis and treatment, roughly 35% will ultimately die of their malignancy. Fortunately, the number of patients living with a cancer diagnosis also continues to expand, anticipated to be more than 19 million in less than a decade. In calculating the relative risks and benefits of therapy, it is therefore important to consider the morbidity and mortality associated with antitumor therapy itself. Significantly, excluding demise due to the malignancy itself, treatment-induced adverse cardiovascular events are the leading cause of death in cancer patients. Chemotherapy, targeted therapies, immune checkpoint inhibition, and radiation therapy can all adversely impact cardiac function, and their effects can be synergistic. Consequently, it is important that possible side effects of therapy be recognized and effectively controlled. This review highlights the mechanisms and histopathologic findings associated with common forms of potentially cardiotoxic cancer therapy including anthracyclines, tyrosine kinase inhibitors, and most recently immune checkpoint (PD-1) inhibitors. Although for many cases the histologic findings are nonspecific, in the appropriate clinical context, therapeutic cardiotoxicity can be inferred and the treatment approach refined appropriately.