Ensuring Superior Reporting of Radiation Therapy Noninferiority Trials: A Systematic Review

PURPOSE: Although the frequency of noninferiority trials is increasing, the consistency of the reporting of these trials can vary. The aim of this systematic review was to assess the reporting quality of radiation therapy noninferiority trials. METHODS AND MATERIALS: The PubMed, Embase, and Cochrane databases were queried for randomized controlled radiation therapy trials with noninferiority hypotheses published in English between January 2000 and July 2022, and this was performed by an information scientist. Descriptive statistics were used to summarize data. RESULTS: Of 423 records screened, 59 (14%) were included after full-text review. All were published after 2003 and open label. The most common primary cancer type was breast (n = 15, 25%). Altered radiation fractionation (n = 26, 45%) and radiation de-escalation (n = 11, 19%) were the most common types of interventions. The most common primary endpoints were locoregional control (n = 17, 29%) and progression-free survival (n = 14, 24%). Fifty-three (90%) reported the noninferiority margin, and only 9 (17%) provided statistical justification for the margin. The median absolute noninferiority margin was 9% (interquartile range, 5%-10%), and the median relative margin was 1.51 (interquartile range, 1.33-2.04). Sample size calculations and confidence intervals were reported in 54 studies (92%). Both intention-to-treat and per-protocol analyses were reported in 27 studies (46%). In 31 trials (53%), noninferiority of the primary endpoint was reached. CONCLUSIONS: There was variability in the reporting of key components of noninferiority trials. We encourage consideration of additional statistical reasoning such as guidelines or previous trials in the selection of the noninferiority margin, reporting both absolute and relative margins, and the avoidance of statistically vague or misleading language in the reporting of future noninferiority trials.