Celebrated physicist Sir Paul Callaghan has ended his experimental intravenous vitamin-C treatment for cancer, saying there is "absolutely no evidence" it worked.
He is concerned that alternative medicine advocates are now using his "unusual experiment" to promote the controversial treatment in a misleading way.
The New Zealander of the Year, who has terminal colon cancer, began receiving high-dose intravenous infusions of vitamin C in June last year, along with several alternative herbal remedies.
The 64-year-old began the treatment during a six-month break from chemotherapy, tracking its effectiveness through a blood test for protein carcinoembryonic antigen (CEA), which indicates cancer levels.
Yesterday, he told The Dominion Post he had ended his experiment after analysing data from six months of blood test results. "I have, as a result, learned enough to say that there is absolutely no evidence of any beneficial effect of high-dose intravenous vitamin C in my case."
His CEA had initially dropped after the first six doses of vitamin C, but had then risen again.
He said he wanted to make the results of his experiment public because of the risk his use of vitamin C would be used to falsely promote the therapy. "I've been deluged with correspondence from people who have wanted me to endorse products, try products. That was a really negative side."
The way people promoted products without evidence was "quite repellent", he said.
He had seen his name cited in articles promoting vitamin C and said he knew publicity about his experiment had caused other people to try it.
People with cancer had the right to try unproven therapies themselves, but should do so in consultation with their specialist or GP, he said.
"In my case, I have done so openly, with the knowledge of my medical advisers, and with the sort of dispassionate scepticism that you would expect of a scientist. I was never advocating this treatment. I was just curious."
He is now receiving radiotherapy and discussing other treatment options with his doctor.
Victoria University professor Shaun Holt, a natural remedies researcher, said he was not surprised the treatment had not worked, "though I really wish it had".
Debate about high-dose vitamin C had been raging for three decades and it was time proper clinical trials were conducted, he said.
"I don't think it does [work], but I'm always happy to be corrected.
"Sir Paul is such a high-profile, well-respected person. It would be great if he could use that profile to initiate the funding for a trial."
High-dose vitamin C has been steadily gaining publicity in New Zealand.
Young Wellington film-maker Kurt Filiga tracked his unsuccessful treatment in a documentary he made before his death from leukaemia in September 2010.
Last year, an unnamed Wellington doctor who gives intravenous vitamin C told The Dominion Post that an estimated 30 clinics nationwide gave 10,000 injections of vitamin C a year.
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