Part III: The potential to ‘repurpose’ familiar drugs to fight cancer rather than pour billions into novel therapies is exciting scientists here and overseas. In Part III of a three-part series, the effects of vitamin C on tumour progression have long excited interest, and an Otago scientist has set out to fully understand the relationship. You can read Part I here and Part II here.
Vitamin C for treating cancer has been the subject of long, controversial debate – with a strong counter argument that it has no value at all. Professor Gabi Dachs of the University of Otago’s Mackenzie Cancer Research Group says she’s agnostic on the matter. “There are the believers and the unbelievers and I’m in neither camp. I’m a scientist and I’m trying to get good, solid data both in model systems in cell culture and animals, as well as, more importantly, in patients with cancer.”
Having worked on the possibilities of vitamin C for nearly two decades, she starts from the premise the vitamin is important to cell function and too little of it means the cells can have markers of being “unhappy”. Using unmanipulated tissue from the He Taonga Tapu Cancer Society Tissue Bank, Dachs’ team measured the vitamin C levels and also the markers of aggression in tumours.
“In all of the cancer types that we looked at so far, we found the more vitamin C you have in the tumour the lower these markers of aggression are.”
Where the markers are higher, it doesn’t necessarily mean the tumours will immediately spread to other parts of the body, says Dachs, but the possibility is there. “It’s a pretty solid link and we’ve seen it in all of the cancers where these pathways are functional. And we’ve looked at a few cancer types, for example in the majority of kidney cancers.”
They also found vitamin C levels dropped in patients undergoing chemotherapy or immunotherapy, especially in comparison with another group of patients who were tested before their tumours were removed.
“The further along in their journey with cancer they were, the lower the vitamin C status. And that’s irrespective of intake.”
Although there was wide variation between them, many patients were borderline deficient, and heading towards getting scurvy. “Our theory at the moment is that something either in the treatment or in the cancer uses up vitamin C.”
One observational study sparked a bit of excitement. When they looked back at samples from the tissue bank, the team could measure vitamin C levels and follow up with the patients years later. They looked at 130 patients with breast, bowel and brain cancer and found those whose tumours had more than average levels of vitamin C before treatment survived longer than those who had less than the average.
The increased survival times ranged from two or three years for those with brain cancer to up to 20 years for those who’d had breast cancer. This led to a small clinical trial of 15 patients with bowel cancer, where a massive 75g of vitamin C was infused into their veins to find out whether the vitamin reached the tumour. And, yes, the dose lifted vitamin C levels significantly in the tumour.
“So that’s a good step forward. [But] we have no data to show whether or not it made any difference to the outcome because it was a very short treatment.”
The researchers have now moved on to another trial of women with endometrial cancer and hopes to recruit 21 patients to strengthen results from the first trial.
SHOULD THE GENERAL POPULATION UP their dose of vitamin C to prevent cancer? The answer’s no – Dachs doesn’t support supplements for healthy people on a good diet. “If you are unwell, it might be worth having a test done to see how your vitamin status is and whether you might need to increase your intake.”
Her goal is to find a way to identify patients for whom vitamin C has a chance of doing some good.
“There’s lots of poor data out there, such as case studies or small trials where vitamin C seems to have done good for patients with cancer. But it’s not replicated in the large randomised clinical trials, which is the gold standard for any new treatment. I believe the reason is that there will be people who respond and people who do not respond. So I’m hoping we can identify what that difference is.”
But funding is a longstanding obstacle. Dachs says about $500,000 would be needed for clinical studies, and only the Health Research Council can offer that level of funding in New Zealand. Apart from a feasibility grant in 2014, numerous applications to the council for funding since 2010 have been unsuccessful.
