Date	Event	Description
22 October 2008	Amended	Converted to new review format.
25 February 2003	New search has been performed	For this minor update, first published in Issue 2, 2003, further data from new reports of two already included trials were incorporated. Trial search update to December 2002. This did not result in a substantive change to the conclusions of the review.
5 February 2002	New search has been performed	A minor update first published in Issue 2, 2002 involved the addition of further data from another report of an already included trial. Trial search update to December 2001. There was no substantive change to the conclusions.
10 April 2001	New citation required and minor changes	A substantive update first published in Issue 3, 2001 involved: Trial search update to April 2001. Inclusion of one new study and of further data from another report of an already included trial. There was no substantive change to the conclusions.
31 July 2000	New citation required and major changes	A substantive update first published in Issue 4, 2000 involved: Trial search update to August 1999. Inclusion of three new studies. Addition of synopsis. Presentation of relative risks instead of Peto odds ratios for dichotomous outcomes. There was no substantive change to the conclusions.