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New research published in the cancer journal Annals of Oncology has reported the existence of spin and bias in a number of published studies of the results and adverse side-effects of Phase III breast cancer trials.

According to researchers at the Princess Margaret Cancer Centre and University of Toronto, a third of all trials failed to demonstrate a statistically significant benefit for the treatment under investigation.

Researchers found that the reports focus on less important, secondary outcomes to show positive interpretation of results.

The presentation of adverse events in two-thirds of the reports was found to be improper as only 32% of articles detailed the frequency of grade III or IV toxicities in the abstract.

The Princess Margaret division of medical oncology and haematology medical oncologist and senior scientist, lead researcher Professor Ian Tannock said more accurate reporting is urgently needed.

"Journal editors and reviewers, who give their expertise on the topic, are very important in ensuring this happens," Tannock said.

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"However, readers also need to critically appraise reports in order to detect potential bias. We believe guidelines are necessary to improve the reporting of both efficacy and toxicity."

Out of 568 randomised, controlled, Phase III breast cancer trials published between January 1995 and August 2011 and identified by Prof Tannock and his colleagues, 164 were eligible for inclusion in the analysis.

"The presentation of adverse events in two-thirds of the reports was found to be improper as only 32% of articles detailed the frequency of grade III or IV toxicities in the abstract."

Prof Tannock and his colleagues defined bias as inappropriate reporting of the primary endpoint and toxicity, with emphasis on reporting of these outcomes in the abstract.

Spin was defined as the use of words in the concluding statement of the abstract to suggest that a trial with a negative primary endpoint was positive based on some apparent benefit shown in one or more secondary endpoints.

Researchers found that 33% trials were reported as positive based on secondary endpoints without having a statistically significant benefit in the primary endpoint.

58% of 92 trials showed no benefit for patients from the experimental therapy (negative primary endpoint), but used secondary endpoints to suggest benefit from the treatment.

Adverse side-effects of the experimental therapy were reported in a biased manner in 67% of papers (110).

Researchers also identified that a small number of studies changed the primary endpoint between registration and outcome reports.

The Princess Margaret clinical research fellow and study first author Dr Francisco Vera-Badillo said; "We found a high incidence of biased reporting of the outcomes of clinical trials. In those with outcomes that were either negative or did not show a statistically significant benefit, spin was used frequently to influence positively the interpretation of the results, by focusing on apparent benefits from secondary endpoints."