A majority of clinical trials report that new treatments are more effective than they turn out to be, finds a study in the Journal of the National Comprehensive Cancer Network. Researchers who analyzed 362 industry-sponsored Phase III randomized oncology trials from 2008 to 2017 found that 58% reported false positive results.

“A false positive result means that a clinical trial concludes that a drug has efficacy when the drug actually does not prolong survival in a clinically meaningful way,” explains lead researcher Changyu Shen, PhD, an associate professor at Harvard Medical School at the time this study was conducted. “False positive results may…expose patients to adverse effects of drugs that are unlikely to produce meaningful health gains.” Patients could also miss the optimal window for receiving other, beneficial treatments while incurring a hefty financial burden, he adds. Shen and colleagues advise a more stringent standard before drug trials even proceed to Phase III.

Shen’s advice for people considering a possible new treatment? Ask your oncologist not just about potential benefits and side effects but also about how confident researchers are in the results. “Patients should seek information on the range of survival benefits instead of just an estimate,” he says. “For example, ‘12 months survival benefit’ is not sufficiently informative, [but] ‘The survival benefit is somewhere between six and 16 months,’ adds more information. It means that with confidence, the survival benefit is at least six months and no more than 16 months for the average patient.”