An examination of research findings revealed almost a third of trials examined failed to find a statistically significant benefit for the treatment, yet still focused on less important outcomes to make them look positive.
The researchers from Princess Margaret Cancer Centre (PMCC) and the University of Toronto also found two-thirds of the trials were biased and under- reported the adverse effects of treatments.
The study, published in the cancer journal Annals of Oncology yesterday, discovered trials showing a significant benefit for treatment were the most likely to downplay side-effects.
In their study, the team analysed 164 “phase-III” clinical trials for breast cancer published between 1995 and 2011.
Phase-III trials, an internationally used term, are run to evaluate the effectiveness and best dosage for therapies already tested in earlier, smaller trials.
They are often the last trial a drug or therapy has to pass before it can be licensed for use in normal clinical practice.
Professor Ian Tannock, who led the research, called for guidelines to be introduced to improve accuracy of reporting.
“Better and more accurate reporting is urgently needed. Journal editors and reviewers, who give their expertise on the topic, are very important in ensuring this happens.”
Prof Tannock, a medical oncologist and senior scientist in the division of medical oncology and haematology at the PMCC, added: “The team said much of the ‘spinning’ involved emphasising a ‘secondary endpoint’ when the ‘primary endpoint’ showed no significant benefit.”
Decided before the trial begins, “primary endpoint” is the specific event measured to see whether or not a treatment works and usually relates to overall survival such as how many patients survive or live longer.
However, there can also be “secondary endpoints” – additional events that are of interest to the investigators but which the study has not been designed specifically to address.
These can include factors such as how much longer patients on the new treatment live without the disease progressing and spreading to other parts of the body or recurring, side-effects and quality of life.
The team found 33 per cent of trials were reported as positive based on secondary endpoints, despite not finding a statistically significant benefit in the primary endpoint.
However, the study concluded that the source of funding for trials – industry or academic – was not associated with bias or spin in the reporting of results and toxicities.
Latest figures from Cancer Research UK show about 4,500 women and 25 men are diagnosed with breast cancer each year in Scotland. Around 1,000 women north of the Border die of breast cancer every year.
Audrey Birt, director of Breakthrough Breast Cancer in Scotland, said: “We strongly believe that making clinical trial data freely available would decrease the potential for ‘spin’ by allowing more researchers to investigate the results. This will ensure trials are accurately assessed by regulatory bodies, allow comparisons with other studies and prevent duplication of trials.
“It is crucial that all clinical trial results are reported fairly, including all negative results.”