Parameter and tested strata p-value
Number of authors: 1-3, 4-6, 7-10, >10 <0.0001
Topic: Breast, Prostate, Lung, others 0.017
Region: USA/Canada, Europe, multiple, others 0.032
Journal: JCO, IJROBP, all others combined 0.049
Type of article: Phase III, other clinical, others >0.2
Table 2: Statistical comparisons (Chi square test).