Antineoplastic drugs can be associated with several side effects, including cardiovascular toxicity (CTX). Biochemical studies have identified multiple mechanisms of CTX. Chemoterapeutic agents can alter redox homeostasis by increasing the production of reactive oxygen species (ROS) and reactive nitrogen species RNS. Cellular sources of ROS/RNS are cardiomyocytes, endothelial cells, stromal and inflammatory cells in the heart. Mitochondria, peroxisomes and other subcellular components are central hubs that control redox homeostasis. Mitochondria are central targets for antineoplastic drug-induced CTX. Understanding the mechanisms of CTX is fundamental for effective cardioprotection, without compromising the efficacy of anticancer treatments. Type 1 CTX is associated with irreversible cardiac cell injury and is typically caused by anthracyclines and conventional chemotherapeutic agents. Type 2 CTX, associated with reversible myocardial dysfunction, is generally caused by biologicals and targeted drugs. Although oxidative/nitrosative reactions play a central role in CTX caused by different antineoplastic drugs, additional mechanisms involving directly and indirectly cardiomyocytes and inflammatory cells play a role in cardiovascular toxicities. Identification of cardiologic risk factors and an integrated approach using molecular, imaging, and clinical data may allow the selection of patients at risk of developing chemotherapy-related CTX. Although the last decade has witnessed intense research related to the molecular and biochemical mechanisms of CTX of antineoplastic drugs, experimental and clinical studies are urgently needed to balance safety and efficacy of novel cancer therapies.

Although survival of patients with different types of cancer has improved, cardiotoxicity induced by anti-neoplastic drugs remains a critical issue. Cardiac dysfunction after treatment with anthracyclines has historically been a major problem. However, also targeted therapies and biological molecules can induce reversible and irreversible cardiac dysfunction. Over the last years, cancer immunotherapies haverevolutionized the clinical management of a wide spectrum of solid and hematopoietic malignancies previously endowed with poor prognosis. Immune checkpoint inhibitors are at the forefront of immunotherapy: the two most prominent are the targeting of cytotoxic-T-lymphocyte-associated antigen 4 (CTLA- 4) and of programmed cell death 1 (PD-1) and its ligand PD-L1. Ipilimumab (anti-CTLA-4) is the godfather of checkpoint inhibitors, whereas several blocking monoclonal antibodies targeting PD-1 (nivolumab and pembrolizumab) and PD-L1 (atezolizumab, durvalumab, avelumab, and BMS-946559) have been developed. Inhibitors of CTLA-4 and PD-1/PD-L1 pathway can unleash anti-tumor immunity and mediate cancer regressions. Although CTLA-4 inhibitors and PD-1 and PD-L1 blocking agents are frequently associated with a wide spectrum of immune-related adverse events, cardiac toxicity has been underestimated. However, early animal studies have demonstrated that after CTLA-4 inhibition and PD-1 deletion autoimmune myocarditis can occur. Moreover, PD-1 and PD-L1 can be expressed in rodent and human cardiomyocytes. During the last years several cases of fatal heart failure have been documented in melanoma patients treated with checkpoint inhibitors. The recent experience with cardiovascular toxic effects associated with checkpoint inhibitors introduces important concepts biologically and clinically relevant for future oncology trials and clinical practice.

Background Influenza vaccination (FV) is recommended for patients with cancer. Recent data suggested that the administration of the FV was associated with an increase in immune-related adverse events (irAEs) among patients on immune checkpoint inhibitors (ICIs). Myocarditis is an uncommon but serious complication of ICIs and may also result from infection with influenza. There are no data testing the relationship between FV and the development of myocarditis on ICIs. Methods Patients on ICIs who developed myocarditis (n = 101) (cases) were compared to ICI-treated patients (n = 201) without myocarditis (controls). A patient was defined as having the FV if they were administered the FV from 6 months prior to start of ICI to anytime during ICI therapy. Alternate thresholds for FV status were also tested. The primary comparison of interest was the rate of FV between cases and controls. Patients with myocarditis were followed for major adverse cardiac events (MACE), defined as the composite of cardiogenic shock, cardiac arrest, hemodynamically significant complete heart block and cardiovascular death. Results The FV was administered to 25% of the myocarditis cases compared to 40% of the non-myocarditis ICI-treated controls (p = 0.01). Similar findings of lower rates of FV administration were noted among myocarditis cases when alternate thresholds were tested. Among the myocarditis cases, those who were vaccinated had 3-fold lower troponin levels when compared to unvaccinated cases (FV vs. No FV: 0.12 [0.02, 0.47] vs. 0.40 [0.11, 1.26] ng/ml, p = 0.02). Within myocarditis cases, those administered the FV also had a lower rate of other irAEs when compared to unvaccinated cases (36 vs. 55% p = 0.10) including lower rates of pneumonitis (12 vs. 36%, p = 0.03). During follow-up (175 [IQR 89, 363] days), 47% of myocarditis cases experienced a MACE. Myocarditis cases who received the FV were at a lower risk of cumulative MACE when compared to unvaccinated cases (24 vs. 59%, p = 0.002). Conclusion The rate of FV among ICI-related myocarditis cases was lower than controls on ICIs who did not develop myocarditis. In those who developed myocarditis related to an ICI, there was less myocardial injury and a lower risk of MACE among those who were administered the FV.