Cancer patients who use alternative therapies may be more likely to shun conventional treatments and risk their chances of survival, research suggests.
The paper's authors said it was likely the results for those who used alternative therapies would have been worse were it not for the fact that they were a group that had better cancer survival chances to begin with.
Although researchers linked the lower chances of survival to refusing or delaying standard treatments, lead author Dr Skyler Johnson, from Yale School of Medicine, told the BBC it was also possible some alternative therapies could interact with conventional treatments and make them less effective.
Dr Johnson said they were more likely to be alternative medicines - treatments that lack clear scientific evidence and are often used in place of conventional care - rather than complementary therapies like yoga or massage, which are usually used alongside standard treatments.
"Although they may be used to support patients experiencing symptoms from cancer treatment, it looks as though they are either being marketed or understood to be effective cancer treatments."
Prof Arnie Purushotham, director at King's Health Partners Comprehensive Cancer Centre, said there was a clear difference between alternative therapies and complementary treatments.