RESEARCH HIGHLIGHTS Nature Reviews Clinical Oncology 11, 180 (2014); published online 25 February 2014; doi:10.1038/nrclinonc.2014.34
Could vitamin C be a useful adjunct to chemotherapy? Nearly four decades ago, intravenous (i.v.) ascorbate (vitamin C) was identified as a potential anticancer therapy, but subsequent trials using oral ascorbate showed no therapeutic benefit. The results of a new study suggest that re-examination of the potential of i.v. vitamin C as an adjuvant cancer therapy is needed. “The pharmacokinetics of oral vitamin C are tightly controlled and blood levels are low, in the micromolar range, whereas i.v. administration bypasses this tight control and blood levels are found to be in millimolar range,” explains Jeanne Drisko, an investigator involved in the new study. “Oral ascorbate is a vitamin, whereas i.v. ascorbate is a drug,” she continues. Indeed, Drisko and colleagues demonstrated that high doses of ascorbate had cytotoxic effects in cancer cells in vitro, but not in nontumorigenic cells, and reduced tumour burden in a mouse xenograft model. Furthermore, ascorbate had a synergistic effect on the antitumour activity of other chemotherapeutic agents.
In women with stage III–IV ovarian cancer (n = 25), high doses of i.v. ascorbate (75–100 g, twice weekly) decreased the frequency of grade 1–2 adverse events associated with first-line paclitaxel and carboplatin chemotherapy, whereas the already low incidence of high-grade events remained unchanged. Although this trial was not powered to demonstrate significant differences in efficacy, prolonged overall survival and time to disease progression were also observed in the patients receiving ascorbate, paclitaxel and carboplatin compared with paclitaxel and carboplatin only. “We are hopeful that the bias from previous erroneous clinic trials of oral ascorbate will cease and that funding will be made available for a large clinical trial of i.v. vitamin C,” Drisko concludes. David Killock Original article Ma, Y. et al. High-dose parenteral ascorbate enhanced chemosensitivity of ovarian cancer and reduced toxicity of chemotherapy. Sci. Transl. Med. 6, 222ra18 (2014)
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