Clinical significance in pediatric oncology randomized controlled treatment trials: a systematic review

Background: Clinical significance in a randomized controlled trial (RCT) can be determined using the minimal clinically important difference (MCID), which should inform the delta value used to determine sample size. The primary objective was to assess clinical significance in the pediatric oncology randomized controlled trial (RCT) treatment literature by evaluating: (1) the relationship between the treatment effect and the delta value as reported in the sample size calculation, and (2) the concordance between statistical and clinical significance. The secondary objective was to evaluate the reporting of methodological attributes related to clinical significance. Methods: RCTs of pediatric cancer treatments, where a sample size calculation with a delta value was reported or could be calculated, were systematically reviewed. MEDLINE, EMBASE, and the Cochrane Childhood Cancer Group Specialized Register through CENTRAL were searched from inception to July 2016. Results: RCTs (77 overall; 11 and 66), representing 95 (13 and 82) randomized questions were included for non-inferiority and superiority RCTs (herein, respectively). The minority (22.1% overall; 76.9 and 13.4%) of randomized questions reported conclusions based on clinical significance, and only 4.2% (15.4 and 2.4%) explicitly based the delta value on the MCID. Over half (67.4% overall; 92.3 and 63.4%) reported a confidence interval or standard error for the primary outcome experimental and control values and 12.6% (46.2 and 7.3%) reported the treatment effect, respectively. Of the 47 randomized questions in superiority trials that reported statistically non-significant findings, 25.5% were possibly clinically significant. Of the 24 randomized questions in superiority trials that were statistically significant, only 8.3% were definitely clinically significant. Conclusions: A minority of RCTs in the pediatric oncology literature reported methodological attributes related to clinical significance and a notable portion of statistically insignificant studies were possibly clinically significance.