Bias in reporting of randomised clinical trials in oncology

Bias in reporting efficacy and toxicity in clinical trials may impact treatment decisions. Here, we report quality of reporting of efficacy and of toxicity in articles describing randomised controlled trials (RCTs) of cancer therapy and the association between biased reporting and study results, funding and financial relationships of the authors with the sponsor.

We reviewed articles published from July 2010 to December 2012 in six high-impact journals reporting RCTs of systemic treatment for cancer. Bias in reporting of the primary end-point and toxicity were assessed. Associations between biased reporting and study results, funding source and financial ties of the author with the funding source were evaluated using logistic regression.

Two hundred articles were identified. Among 107 RCTs where there was no statistically significant difference in the primary end-point between the two arms, 50 (47%) reports used biased reporting in the abstract of the paper to imply benefit of the experimental treatment. Toxicity was not reported in the abstract in 18.5% of the studies and this was associated with a positive primary end-point. Source of funding and financial ties were not associated with biased reporting.

Bias in reporting of efficacy outcomes is common for studies with a negative primary end-point and can lead to off-label misuse of experimental therapies, if they are approved for other indications. Toxicity is under-reported, especially for studies with a positive primary end-point, leading to a biased view of the safety of new treatments.