The Early Breast Cancer Trialists' Collaborative Group (EBCTCG) overview is probably the largest collaborative effort investigating the treatment of people with cancer, in that it seeks to bring together individual participant data from the several hundred randomised trials of interventions for women with breast cancer, in which death was a main outcome, that have taken place over the last half century and more.

The overview takes place in 5 year cycles of study identification; data collection, processing and analyses; presentation and discussion of the results by the collaborating researchers; and publication of these results. Details of the data items being collected for the EBCTCG overview based in Oxford are available at http://www.ctsu.ox.ac.uk/projects/ebctcg.

The Cochrane Breast Cancer Group ensures not to replicate the efforts of the EBCTCG individual-participant data reviews.