Study: Bias in reporting of breast cancer trials
But no industry influence indicated
A study by Canadian researchers shows that many published breast cancer studies are biased to show a positive outcome.
The study, published in Annals of Oncology, looked at the quality of reporting the primary endpoint (PE) and toxicity of randomized clinical trials of breast cancer drugs. The authors searched PubMed for publications between January 1995 and August 2011, excluding trials with sample sizes less than 200, commentaries, review articles, ongoing studies, and articles for which only the abstract was available. For the study, “bias” was defined as “inappropriate reporting of the PE and toxicity, with emphasis on reporting of these outcomes in the abstract,” and “spin” defined as “use of reporting strategies to highlight that the experimental treatment is beneficial, despite a statistically non-significant difference in the primary outcome, or to distract the reader from statistically non-significant results.”1
The researchers from the Princess Margaret Cancer Centre looked at 164 published trials. Of those, 33% showed bias in primary endpoint reporting and 67% in the reporting of toxicity. The primary endpoint was more likely to be reported in the concluding statement of the abstract when significant differences favoring the experimental arm were shown; 59% of 92 trials used a secondary endpoint to show drug benefit when the primary endpoint was not achieved. Only 32% of articles indicated the frequency of grade 3 and 4 toxicities in the abstract. A positive primary endpoint was associated with underreporting of toxicity.1
“[S]pin was used frequently to influence, positively, the interpretation of negative trials by emphasizing the apparent benefit of a secondary end point,” the researchers note.
Most studies were published in prestigious medical journals, the study authors found. Thirty trials were included in ClinicalTrials.gov, and among those, the primary endpoint was changed in the final report in seven studies. Industry funding was reported in 103 studies, 32 studies were funded by academic or governmental grants, and funding source was not stated in 29. While the majority of the examined studies were funded by industry partners, the authors state “we found no association between industry sponsorship and biased reporting of either efficacy or toxicity, and no association of for-profit sponsorship with change of the PE between that listed in trial registries and the final publication.”1
“[B]ias in the reporting of efficacy and toxicity remains prevalent. Clinicians, reviewers, journal editors and regulators should apply a critical eye to trial reports and be wary of the possibility of biased reporting. Guidelines are necessary to improve the reporting of both efficacy and toxicity,” the study authors concluded.
Reference
- F. E. Vera-Badillo, R. Shapiro, A. Ocana, E. Amir, and I. F. Tannock. Bias in reporting of end points of efficacy and toxicity in randomized, clinical trials for women with breast cancer. Ann. Onc. January 2013: mds636v1-mds636.
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