Researchers reviewed data from 930 clinical trials published in 10 leading medical journals between early 2007 and mid-2015. The investigators found that a significant number of early trials reported effects that were 2.7 times greater than what was eventually seen in later trials.
"This phenomenon of exaggerated early results was present in a whopping 37 percent of the studies we reviewed," said study author Dr. Fares Alahdab, a research fellow with the Mayo Clinic's Evidence-Based Practice Center.
"Physicians and patients should be cautious about new or early clinical trial evidence. Exaggerated results could lead to false hope as well as possibly harmful effects," Alahdab added in a Mayo news release.
The review focused on clinical trials for drugs or devices targeting chronic conditions, including cancer, stroke, heart disease, diabetes and kidney disease.
According to Dr. M. Hassan Murad, director of Mayo's Evidence-Based Practice Center, "Often, patients are living with more than one chronic condition, and they and their doctors watch for research about new treatments. They need to be aware that the effect seen in earlier trials may not bear out over time and may be much more modest."
Murad noted that "some people may think this is an anti-innovation message."
But, he added, "To the contrary, we welcome new treatments. We just want people to know that the benefit seen in real practice, when treatments are given to people with various co-morbidities [multiple illnesses] and in different settings, may be smaller than what was seen in the earliest clinical trials."
According to the U.S. National Institutes of Health, clinical trials are key to all medical advances. They look at new ways to prevent, detect or treat disease. They can involve new drugs or new combinations of drugs, new ways of doing surgery, and new medical devices, among other topics.
The study was published online Feb. 21 in the journal Mayo Clinic Proceedings.More information
The U.S. National Institutes of Health has more on clinical trials.
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