A new study carried out by the Princess Margaret Cancer Centre in Toronto claims that researchers and academics regularly downplay negative results of clinical studies while amplifying their positive aspects.

It also found that reports of clinical trial results in medical journals regularly published serious side effects in small print only.

Medical oncologist and leader of the research Professor Ian Tannock and his colleagues studied the results of 164 large scale (Phase III) trials reported in journals and found evidence of large-scale misreporting of clinical trial results.

Such tactics can mislead doctors by not making all the facts about a drug’s clinical trial abundantly clear, leading doctors to wrongly prescribe drugs to patients.

"Medical oncologist and leader of the research Professor Ian Tannock and his colleagues studied the results of 164 large scale (Phase III) trials reported in journals and found evidence of large-scale misreporting of clinical trial results."

Some researchers even changed the primary endpoint objective of a trial halfway through, perhaps because early results indicated the trial was going to fail otherwise.

Writing in the journal Annals of Oncology, Tannock and his colleagues concluded; "These reports were biased and used spin in attempts to conceal that bias."

They also noted bias reporting of side effects in two-thirds of papers, with negative events only reported in small print, particularly if the trial met its primary endpoint.

They commented; "A possible explanation for this could be that the investigators, sponsors or both, prefer to focus on the efficacy of the experimental treatment and downplay toxicity to make the results look more attractive."

They also discovered that in a third of all trials that failed to meet their primary endpoints, this fact was downplayed and the less important secondary endpoint was focused on.

Breakthrough Breast Cancer research manager Richard Francis, speaking to The Daily Telegraph, said; "It is crucial that all clinical trial results are reported fairly, including all negative results and possibly harmful side effects of any new treatments."

He added that secondary endpoints are also important; "While it is imperative that survival remains the main aim in these trials, we know from speaking to women who have suffered from breast cancer how important other factors are, including quality of life, side effects and the extended time a patient is able to control the growth of their disease."