A new clinical trial shows that a high dose of vitamin C can improve health outcomes for patients who are undergoing conventional cancer treatment.
Since then, further studies in animals and cancer cell cultures suggested that a high concentration of ascorbic acid might prevent and treat cancer.
More recent studies have examined the combined effect of high-dose vitamin C and conventional cancer treatment. Some of this research showed that patients who received the combined treatment had a slower progression of the disease, while others have suggested that the side effects of chemotherapy were less pronounced among those who also took high doses of vitamin C.
To obtain a high dose in these studies, vitamin C is usually administered using intravenous infusion. Vitamin C has a short half-life of only 2 hours in the human body, which is why it must be administered in high doses as a treatment.
A new clinical trial studies the effect of giving between 800 and 1,000 times the daily recommended dose of vitamin C to patients with brain and lung cancer.
The new research was led by scientists at the University of Iowa in Iowa City, and the results were published in the journal Cancer Cell.
Vitamin C passes human safety trial
As part of the human safety trial, 11 patients with brain cancer who were undergoing standard chemotherapy and radiation therapy were also administered three weekly intravenous infusions of vitamin C for 2 months, and then two weekly infusions for 7 months.
Each infusion raised the patients' blood levels of vitamin C to 20,000 micromoles (μM). The average level of vitamin C in adults is approximately 70 μM.
This safety test was the first phase of a series of clinical trials that will investigate whether high-dose vitamin C can effectively increase the lifespan and quality of life for patients that are being treated with chemotherapy and radiation therapy.
For now, the data from the phase I trial show that patients with glioblastoma survived for 4 to 6 months longer than the average survival time noticed in patients who undergo conventional treatment alone. Specifically, patients who also received high doses of ascorbic acid survived for 18 to 22 months compared with 14 to 16 months, which is the typical survival rate for glioblastoma.
For the upcoming phase II of the clinical trials, the scientists will examine the effects of vitamin C in participants with stage 4 lung cancer as well as in those with highly aggressive brain tumors, such as glioblastoma.
How vitamin C weakens cancer cells
The mechanism that might explain the potential efficacy of vitamin C in treating lung and brain cancer relates to the cancer cells' metabolism.
As a consequence of the faulty metabolism that occurs inside the cancer cells' mitochondria, these cells produce abnormally high levels of so-called redox active iron molecules. These molecules react with vitamin C and form hydrogen peroxide and hydrogen peroxide-derived free radicals.
Scientists think that these free radicals drive cancer cell death by damaging the cells' DNA. The free radicals are also thought to weaken the cancer cells and make them more vulnerable to radiation therapy and chemotherapy.
"This paper reveals a metabolic frailty in cancer cells that is based on their own production of oxidizing agents that allows us to utilize existing redox active compounds, like vitamin C, to sensitize cancer cells to radiation [therapy] and chemotherapy."
Garry Buettner, study co-author
Co-senior author Douglas Spitz also comments on the significance of the findings:
"This is a significant example of how knowing details of potential mechanisms and the basic science of redox active compounds in cancer versus normal cells can be leveraged clinically in cancer therapy," he explains. "Here, we verified convincingly that increased redox active metal ions in cancer cells were responsible for this differential sensitivity of cancer versus normal cells to very high doses of vitamin C."
If the approach proves effective in future clinical trials as well, the new treatment could also be significantly less costly than the standard treatment. To put this into perspective, 9 months of intravenous vitamin C treatment as part of the phase II trial currently costs less than one dose of chemotherapy.
"The majority of cancer patients we work with are excited to participate in clinical trials that could benefit future patient outcomes down the line. Results look promising but we are not going to know if this approach really improves therapy response until we complete these phase II trials."
Bryan Allen, co-senior author