Factors associated with publication of randomized phase iii cancer trials in journals with a high impact factor

Impact factor (if) is often used as a measure of journal quality. The purpose of the present study was to determine whether trials with positive outcomes are more likely to be published in journals with higher ifs.

We reviewed 476 randomized phase iii cancer trials published in 13 journals between 1995 and 2005. Multivariate logistic regression models were used to investigate predictors of publication in journals with high ifs (compared with low and medium ifs).

A positive outcome had the strongest association with publication in high-if journals [odds ratio (or): 4.13; 95% confidence interval (ci): 2.67 to 6.37; p < 0.001]. Other associated factors were a larger sample size (or: 1.06; 95% ci: 1.02 to 1.10; p = 0.001), intention-to-treat analysis (or: 2.53; 95% ci: 1.56 to 4.10; p < 0.001), North American authors (or for European authors: 0.36; 95% ci: 0.23 to 0.58; or for international authors: 0.41; 95% ci: 0.20 to 0.82; p < 0.001), adjuvant therapy trial (or: 2.58; 95% ci: 1.61 to 4.15; p < 0.001), shorter time to publication (or: 0.84; 95% ci: 0.77 to 0.92; p < 0.001), uncommon tumour type (or: 1.39; 95% ci: 0.90 to 2.13; p = 0.012), and hematologic malignancy (or: 3.15; 95% ci: 1.41 to 7.03; p = 0.012).

Cancer trials with positive outcomes are more likely to be published in journals with high ifs. Readers of medical literature should be aware of this "impact factor bias," and investigators should be encouraged to submit reports of trials of high methodologic quality to journals with high ifs regardless of study outcomes.