Characterization of Vascular Functions in Myeloma Patients Before and During Anti-tumor Therapy

Treatment options for multiple myeloma have increased significantly over the last years with the approval of immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs). These therapies have markedly improved overall survival for these patients to a median of 5-7 years, many continue to live for more than 10 years. Due to the advanced age, the myeloma patient collective has a high prevalence of pre-existing cardiovascular comorbidities. In addition, the primary disease process contributes to cardiovascular complications. With the beginning of anti-tumor therapy, an increased incidence of cardiovascular complications in myeloma patients can be determined. This includes hypertension, left ventricular dysfunction, heart failure and both arterial and venous thromboembolic events.

Proteasome inhibitors including bortezomib and carfilzomib, and immunomodulatory agents, e.g. lenalidomide, represent cornerstone therapies for multiple myeloma. The most common therapy choices are Bortezomib-based therapy (VCD, VC) and Carfilzomib-based therapy (KRD, KD). Induction therapy is given 4-6 cycles followed by autologous hematopoietic cell transplantation. Thereafter, many patients receive consolidation therapy. In patients not eligible for autologous hematopoietic cell transplantation, a prolonged course of initial chemotherapy is typically administered. The proteasome inhibitor Bortezomib is used predominately in the front line setting, while second-generation carfilzomib is used in relapsed/refractory disease.

Despite their efficacy, increased rates of cardiovascular complications occur in patients exposed to these particular therapies. Higher incidences of cardiac adverse events including hypertension, arrhythmia, heart failure, ischemic heart disease and cardiomyopathy has been reported in patients receiving carfilzomib and bortezomib. Immunomodulatory agents are known to increase the risk of venous thromboembolic disease particularly when combined with dexamethasone or other chemotherapy. Furthermore, increased incidence of myocardial infarction (MI) and cerebrovascular events has been demonstrated in patients treated with lenalidomide. The mechanism of PI- and IMiD-associated cardiotoxicity is not fully elucidated. PIs inhibit proteasome activity, leading to the accumulation of abnormal proteins which in turn activates apoptotic pathways in myeloma cells. IMiDs bind cereblon, a component of the E3 ubiquitin ligase which promotes proteasome-mediated degradation of the transcription factors, IKZF1 and IKZF. It is unclear if the protein degradation properties of these drugs contribute to cardiotoxicity, although clinical features of the toxicity suggest endothelial cell injury and dysfunction. It is possible that CV events may be augmented when these two classes of medications are co-administered and further enhanced by the additional endothelial stress conferred by steroids. The detailed mechanism by which proteasome inhibitors and immunomodulatory agents lead to increased cardiovascular events is not established at this time.

Endothelial dysfunction, as a possible mechanism of cardiovascular toxicity, is difficult to assess. Flow-mediated dilation (FMD) is an noninvasive method to measure endothelial function by assessing the change in the vasodilatative reserve of the brachial artery. Several independent recent investigations implicate that vascular (endothelial) dysfunction precedes hypertension and heart failure. This has been related to a reduced level of metabolites of the l-arginine-nitric oxide (NO) signaling pathway.

Hypothesis: