Is it proper to stop participant recruitment in a clinical trial when a treatment or control group has been shown to be statistically significant?

Question

"The study was randomized and double-blind. It was designed to be discontinued when interim statistical analysis found a significant difference in favour of one of the groups. This happened when 45 patients had been enrolled; consequently the study was discontinued. Data were analysed with the Mann-Whitney U test, or the X2 test where appropriate. P < 0 05 was considered statistically significant"

Answer 1

Stopping participant recruitment early in a clinical trial due to statistically significant results can be appropriate, but only if interim analyses and stopping rules were planned in advance and proper statistical adjustments were made for multiple analyses. Early stopping without these safeguards can introduce bias, overestimate treatment effects, and increase the risk of false positive results. Regulatory guidelines and best practices require pre-specified rules and adjusted significance thresholds; otherwise, stopping early is not considered methodologically sound.