Crowdfunding appeals for cancer treatment are fuelling the use of alternative "quack" therapies, experts have warned.
About £8 million has been raised for alternative cancer treatments on UK crowdfunding sites since 2012, according to figures published in the British Medical Journal (BMJ).
The findings have led to calls for sites such as JustGiving and GoFundMe to vet cancer appeals to stop patients and donors being exploited.
The figures, collected by anti-pseudoscience charity The Good Thinking Society, showed that most of the money raised was for treatment abroad, with many of the therapies not backed by scientific evidence.
The society's project director, Michael Marshall, said: "We are concerned that so many UK patients are raising huge sums for treatments which are not evidence-based and which in some cases may even do them harm."
Appeals for alternative treatments which refer to drugs that have been discredited, extreme dietary regimes, intravenous vitamin C, and alkaline therapy should be rejected outright, said Mr Marshall.
He added: "If these platforms want to continue to benefit from the goodwill of their users - and, indeed, to profit from the fees they charge each of their fundraisers - they have a responsibility to ensure that they do not facilitate the exploitation of vulnerable people."
Edzard Ernst, professor of complementary medicine at Exeter University, also supported the call, pointing out that crowdfunding organisations already reject appeals involving violence or illegal activity, such as terror attacks.
He told the BMJ: "Crowdfunding for a terror attack is out of the question. Crowdfunding for cancer quackery is not any better and must be stopped."
JustGiving's own figures show more than 2,300 UK cancer-related appeals were set up on its site in 2016, a seven-fold rise from the previous year.
GoFundMe said it was already "taking proactive steps" in the US to make sure users of its site were better informed, and would be doing the same globally over the coming months.
JustGiving told the BMJ: "We don't believe we have the expertise to make a judgment on this."
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