Important changes to methods after trial commencement
stoma
COMPLICATION
The trial period was prolonged by 2 years, as the inclusion rate was slower than anticipated and due to different times of start-up in the participating centres. The initial power calculation was based on the assumption of a 5% complication rate in the early stoma reversal group and 30% in the late stoma reversal group. With a power of 80% and a 5% significance level, 75 patients in each group would be required (nQuery Advisor 6.01; GraphPad Software DBA Statistical Solutions, San Diego, USA). As we expected that at least 25% would have to be excluded because of operative deviation from the planned LAR with a diverting ileostomy or other reasons, at least 200 patients were needed.An interim analysis (01.11.2015) after inclusion of half of the patients showed no differences in the complication rates between the two groups and considerably lower than the 30%. By continuing the study by registration of the complication rate, only, a type 2 error in the interpretation of the results might be a risk. Therefore, CCI was considered more appropriate to use. With the initial intention to include 150 patients our power calculation showed that a difference in CCI on 5 between the two groups would be significant. This was considered clinically relevant, as we would go for only a small difference in the argument to change from a late to an early stoma reversal in the clinical setting.