Introduction The TOPPIC trial is a UK based randomised control trial of 6-mercaptopurine vs placebo in the prevention of post operative Crohn's disease originally conceived, designed and powered in 2003, but recruiting its first patient in 2008. During this period there has been a substantial increase in the availability and use of biologic agents for the treatment of Crohn's disease.

Methods As recruitment to the TOPPIC trial proceeded, it became apparent that actual recruitment did not match that projected. Therefore prior to an expansion of the centres to include sites across the UK, analysis of the resection figures from the initial sites (Aberdeen, Dundee, Edinburgh and Glasgow) was undertaken by retrospective review of data held by each centre regarding the number of ileocolonic resections with primary anastamosis performed for the 6-year period 2003–2008.

Results Complete data for this period were available from two of the five initiating sites (Dundee and Glasgow) representing a total of 237 resections and a median number of resections of 43.5 per year (range 40–56). Across the 6 years there was an overall reduction in the number of resections with a linear correlation coefficient of R²=0.47 representing a 26% reduction in the number of resections from 2003 to 2008. This downward trend was more pronounced in Dundee with a median number of resections of 27.5 per year and a linear correlation coefficient R²=0.47 comprising an increase in the first 3 years and then a significant reduction from 2005 to 2008 (p=0.025). Glasgow with a median number of resections of 18.5 per year also had an overall downward trend with a linear correlation coefficient of R²=0.03 which consisted of a marked initial reduction that then stabilised at the reduced rate.

Conclusion The reduction in surgical resection rates is likely to be multifactorial but the concurrent increase in the use of biological therapies in the UK is further circumstantial evidence that these therapies alter the natural history of Crohn's disease. The TOPPIC trial continues to recruit across the UK and will be in a position to report further on this important observation regarding the number of ileocolonic resections in addition to the trial primary endpoint.