Jump to text | Accessibility

Clinical Trial Service Unit & Epidemiological Studies Unit

CTSU

Need for large-scale randomised evidence

When important causes of disease are to be assessed, the effects of those causes are sometimes so extreme that the cause-and-effect relationships can be reliably inferred from purely observational studies of sufficiently large size (such as those of smoking and lung cancer, smoking and myocardial infarction (MI), blood lipids and MI, or blood pressure and stroke). Unfortunately, when assessing the treatment of some disease, there may well be only moderate improvements in outcome. Just a moderate survival improvement in a common disease might, however, save thousands of lives a year (and prevent much disability), so it is important not to get wrong answers. The best way to obtain reliable results about moderate treatment effects is by getting large-scale randomised evidence, as large numbers avoid being misled by the play of chance and proper randomisation avoids being misled by any biases.

Meta-analyses of trials

As one way of achieving this, CTSU established the use of collaborative systematic "meta-analyses" of randomised trials that have all addressed much the same question [1-5]. In breast cancer, for example, CTSU has set up a collaboration between everybody in the world who has ever organised a randomised trial comparing different treatments for "early" breast cancer [6-13]. Among other things, this showed clearly that a few years of tamoxifen (which is a relatively inexpensive and non-toxic hormonal treatment) can significantly improve ten-year survival, as can multiple-drug chemotherapy -- and the resulting change in medical practice has led to the avoidance of tens of thousands of deaths each year. In neoplastic disease, CTSU is coordinating worldwide meta-analyses of leukaemia trials and, with other units, of colorectal and prostate cancer trials. It has also established similar large-scale collaborative meta-analyses in cardiovascular disease. Regular updates, incorporating further follow-up and new trials, ensure that the results become more and more widely relevant.

Current research

  • (ATT) Antithrombotic Trialists' Collaboration
  • (CTT) Cholesterol Treatment Trialists' Collaboration
  • (EBCTCG) Early Breast Cancer Trialists' Collaborative Group
  • (FTT) Fibrinolytic Therapy Trialists' Collaborative Group
  • (PCTCG) Prostate Cancer Trialists Collaborative Group
  • Collaborative meta-analyses of leukaemia trials
  • (Coxib) Collaborative meta-analyses of COX-2 Inhibitor (Coxib) and non- steroidal anti-inflammatory drug (NSAID) trials

Mega-trials

CTSU also established the use of very large streamlined randomised trials, or "mega-trials", to assess the effects of widely practicable treatments on mortality and major morbidity in common diseases [1-5]. Such trials typically randomise some tens of thousands of patients and, as a result, have provided clear and reliable information about the effects of several treatments. In cardiovascular disease, CTSU designed and ran the four International Studies of Infarct Survival (ISIS-1 to ISIS-4: randomising 140,000 patients [14-17]), whose results have substantially improved the emergency treatment of heart attacks -- and, consequently, are saving tens of thousands of lives each year. CTSU is currently conducting several mega-trials of the effects of different treatments for vascular diseases and for cancers (as well as for certain other conditions). In addition the unit runs all of the Medical Research Council leukaemia trials, and helps others with trial design, conduct and analysis.

Current research

Back to Projects page.
Back to About CTSU.

Last modified 09-06-2006 12:20 PM

Current Section