Phase 3 randomized controlled trials (RCTs) are used to evaluate clinically important differences in efficacy and safety. These trials are known as the gold standard to evaluate new drugs before regulatory approval. Biased reporting and selective publication can, however, create false perceptions of efficacy and safety.

The authors of (1) searched PubMed from 1995 to 2011 to identify RCTs for breast cancer and assessed the bias in the reporting of primary endpoints and of toxicity. Changes in endpoints were detected by comparing with the information registered in the ClinicalTrials.Gov registry and funding sources.

Of 164 included trials 33% showed bias in the reporting of primary endpoint and 67% in the reporting of toxicity. Of 92 trials with a negative primary endpoint 59% used secondary endpoints to suggest beneficial effects of the treatment. Positive primary endpoints were also associated with under-reporting of toxicity.

The authors conclude that bias in the reporting of outcome is common for studies with negative primary endpoints, and that the reporting of toxicity is especially poor for studies with positive primary endpoints.

Reference

1. Vera-Badillo FE, Shapiro R, Ocana E, Tannock IF. Bias in reporting of end points of efficacy and toxicity in randomized, clinical trials for women with breast cancer. Ann Oncol 2013 DOI: 10.1093/annonc/mds636.