The Canadian Study of Arterial Inflammation in Patients with Diabetes and Recent Vascular Events, Evaluation of Colchicine Effectiveness (CADENCE): protocol for a randomised, double-blind, placebo-controlled trial

Background Inflammation is a key mediator in the development and progression of the atherosclerotic disease process as well as its resultant complications, like myocardial infarction (MI), stroke and cardiovascular (CV) death, and is emerging as a novel treatment target. Trials involving anti-inflammatory medications have demonstrated outcome benefit in patients with known CV disease. In this regard, colchicine appears to hold great promise. However, there are potential drawbacks to colchicine use, as some studies have identified an increased risk of infection, and a non-significant trend for increased all-cause mortality. Thus, a more thorough understanding of the underlying mechanism of action of colchicine is needed to enable a better patient selection for this novel CV therapy. Objective The primary objective of the Canadian Study of Arterial Inflammation in Patients with Diabetes and Recent Vascular Events, Evaluation of Colchicine Effectiveness (CADENCE) trial is to assess the effect of colchicine on vascular inflammation in the carotid arteries and ascending aorta measured with 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT in patients with type 2 diabetes mellitus (T2DM) or pre-diabetes who have experienced a recent vascular event (acute coronary syndrome (ACS)/MI, transient ischaemic attack (TIA) or stroke). Secondary objectives include determining colchicine’s effect on inflammatory biomarkers (high-sensitivity C reactive protein (hs-CRP) and interleukin-6 (IL-6)). Additionally, we will assess if baseline inflammation imaging or biomarkers are associated with a treatment response to colchicine determined by imaging. Exploratory objectives will look at: (1) the difference in the inflammatory response to colchicine in patients with coronary events compared with patients with cerebral events; (2) the difference in the inflammatory response to colchicine in different vascular beds; (3) the relationship of FDG-PET imaging markers with serum biomarkers and (4) assessment of quality-of-life changes. Methods and design CADENCE is a multicentre, prospective, randomised, double-blinded, placebo-controlled study to determine the effect of colchicine on arterial inflammation as assessed with imaging and circulatory biomarkers, specifically carotid arteries and aortic FDG uptake as well as hs-CRP and IL-6 among others. Patients with T2DM or pre-diabetes who have recently experienced a CV event (within 30–120 days after an ACS (ie, ST-elevation MI (STEMI) or non-STEMI)) or TIA/stroke with documented large vessel atherosclerotic disease will be randomised to treatment with either colchicine 0.6 mg oral daily or placebo. Participants will undergo baseline clinical evaluation including EQ5D assessment, blood work for inflammatory markers and FDG PET/CT scan of the ascending aorta and left and right carotid arteries. Patients will undergo treatment for 6 months and have repeat clinical evaluation including EQ5D assessment, blood work for inflammatory markers and FDG PET/CT scan at the conclusion of the study. The primary outcome will be the change in the maximum target to background ratio (TBR max ) in the ascending aorta (or carotid arteries) from baseline to follow-up on FDG PET/CT imaging. Discussion Colchicine is an exciting potential new therapy for CV risk reduction. However, its use is associated with side effects and greater understanding of its underlying mechanism of action is needed. Importantly, the current study will determine whether its anti-inflammatory action is an indirect systemic effect, or a more local plaque action that decreases inflammation. The results will also help identify patients who will benefit most from such therapy. Trial registration number NCT04181996 .