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The Cholesterol Treatment Trialists’ (CTT) Collaboration was established in 1994, with its initial protocol being published in 1995. It was set up after it was recognized that no single lipid intervention trial would be likely to have a sufficient number of trial participants (and hence statistical power) to reliably assess mortality outcomes or look at events in particular types of patient. Its aim is to conduct periodic meta-analyses of large-scale (≥1000 participants), long-term (≥2 years scheduled treatment duration) unconfounded, randomized controlled trials of lipid intervention therapies.

The Collaboration's work to date has largely focused on statin therapy, with individual participant data on major vascular events, cancers and mortality having been collected from about 30 major statin trials (equating to approximately 175,000 trial participants). The analyses of such data have been published in a series of publications, sequentially adding to the body of evidence for the efficacy and safety of statins. These analyses have shown that:

  • Reduction of LDL cholesterol using statin therapy substantially reduces the risk of major vascular events (major coronary events, strokes or the need for coronary revascularization) and vascular mortality by about one fifth for each 1 mmol/L reduction in LDL cholesterol achieved
  • Further reductions in LDL cholesterol with more intensive statin therapy produce further reductions in the incidence of major vascular events

In addition, the CTT analyses have shown that statin therapy:

  • Has no effect on the incidence of, or death from, any type of cancer
  • Is effective in a wide range of people including those with diabetes, those at low risk of vascular disease, and in both women and men

A new programme of work is currently underway to collect and analyze individual participant data on all other types of adverse event that were recorded in large-scale statin trials, in order that comprehensive analyses of all possible effects (either adverse or beneficial) of statin therapy in these trials can be conducted. This is a substantial undertaking, and methods have been developed to convert the extensive and heterogenous data into a single analysable format through use of systems based upon commonly used standards including the Clinical Data Interchange Standards Consortium Study Data Tabulation Model (CDISC SDTM) and the Medical Dictionary for Regulatory Activities (MedDRA).

The CTT Collaboration also has plans to combine data from randomized trials of other lipid modification therapies, both for established drugs (such as fibrates) and emerging interventions (such as PCSK9 or CETP inhibitors).

Dr Roger Blumenthal, Professor of Medicine and Director of Johns Hopkins Ciccarone Center for the Prevention of Heart Disease

Christopher Cannon MD, Senior Physician, Brigham and Women's Hospital; Professor, Harvard Medical School

Dr Jennifer Robinson, Professor of Epidemiology, College of Public Health Professor of Internal Medicine University of Iowa Carver College of Medicine