According to the latest research breast cancer studies funded by drug companies are more likely to come up with positive findings than those without pharmaceutical industry backing.
The study which is the latest to find industry-funded research produces more positive results, also found that industry-backed studies have a tendency to be designed differently than others and raises the possibility that drug companies may simply back the least-risky alternatives.
The research team from the University of North Carolina School of Medicine at Chapel Hill and the Dana Farber Cancer Institute, suggest the same may be true for similar findings on heart, stroke and bone marrow cancer research.
Consumer advocates said the findings raise questions about the integrity of company-funded research as the industry spends billions of dollars annually to bring new, potentially lucrative drugs to the market.
The pharmaceutical industry has denied that studies are adjusted to produce positive findings.
Dr. Jeffrey Peppercorn and colleagues looked at 140 studies published in 2003, 1998 and 1993 in 10 medical journals on breast cancer therapies, nearly half of which had drug company involvement in the form of funding, provision of drugs or participation of a company scientist.
Their main focus was on 2003 because it was difficult to determine industry involvement in the earlier studies; they found that 58 percent of the studies had industry backing; of this number 84 percent showed positive results, compared to 54 percent for other studies.
Dr. Peppercorn says there are several potential explanations; either the results are biased and negative studies are not being published, or the results are being interpreted favorably.
He says there is also the possibility that companies were taking "safer bets" by making sure they proceeded to costly clinical trials with drugs that had a good chance of doing well.
Peppercorn says that this does not imply that the pharmaceutical industry is doing anything wrong and he says they are excellent at developing new therapies, but if more and more research is funded by drug companies, then the limited amount of funding coming from other sources may need to be directed to address other questions.
The researchers found that in the 2003 studies, 66 percent of industry-backed research involved "single-arm" studies where all the patients received the same treatment, and no control group were given another treatment to compare effectiveness, as against 33 percent of the other studies.
The company-sponsored trials also appeared to target patients with advanced disease.
Peppercorn says in industry-backed trials questions regarding evaluation of the toxicity of drugs to particular groups of patients may not be addressed.