The first-ever study conducted to examine the impact of the pharmaceutical industry on breast cancer research has concluded that clinical trials which are supported by drugmakers are more likely to report positive results than those that are not.

There are also “significant differences” in the design of trials and types of questions which industry-sponsored trials address compared to those without company sponsorship, says the study, which will appear in the April 1, 2007 issue of the American Cancer Society journal Cancer.

The authors, led by Jeffrey Peppercorn of the University of North Carolina at Chapel Hill School of Medicine, acknowledge that the industry is a “significant contributor” to the R&D which is critical to developing new therapies, and that it spends far more than the US National Institutes of Health (NIH). However, they add that, as collaborations between the “for-profit” drug industry and academic medical centres increase, concern has grown over the impact of for-profit sponsorship on the nature and quality of the research and the potential for conflicts of interest. Studies in other areas of medicine have suggested that pharmaceutical sponsorship leads to a greater chance that a clinical trial will yield positive results, but the importance of this for patients and researchers, and whether this is also the case in cancer research, are not yet clear, they say.

Therefore, the authors reviewed 140 studies reporting breast cancer therapy results published over the past decade in select journals at five-year intervals. They discovered that 67 (48%) of the studies reported some form of drug company involvement – through co-authorship, supply of drug or financial support – and that company participation increased from 44% in 1993 to 58% in 2003.

Most importantly, studies involving drugmakers were found to be more likely to report positive results favouring the experimental therapy and significantly more likely to use “single arm” designs – where patients get the same treatment with no control group to compare efficacy. Company-sponsored trials also tend to target patients with advanced disease, the researchers add.

While these types of studies are important for identifying new effective drugs, they may not answer questions about optimal dosing, duration and identification of patients who may have better or worse outcomes on treatment, and these are important clinical factors for treatment guidelines, the authors comment.

The impact of growing pharmaceutical industry involvement in breast cancer research appears to be similar to the case elsewhere in medical R&D, they conclude, and warn that this relationship “may yield better therapies for treatment of breast cancer, but at the same time focus research on some clinical problems while neglecting others.” Lynne Taylor