To the Editor: For more than 30 years, the medical profession has had lingering questions about the efficacy of vitamin C in cancer therapy. Initial clinical reports¹ and early preclinical studies² indicated that vitamin C administered intravenously may have potential anticancer benefits. Yet, few definitive clinical reports supporting this finding have been published. Thus, in October 2006, Cancer Treatment Centers of America (CTCA) initiated a US Food and Drug Administration–approved phase 1 study of intravenous vitamin C for patients with solid tumors who have exhausted all other available treatments. The investigators include an osteopathic internist (C.M.S.), a medical oncologist (R.D.L.), and a clinical epidemiologist (C.G.L.). 

High doses (30 g/m² to 130 g/m²) of vitamin C are used to achieve blood levels greater than the 20 mM that have been reported to be cytotoxic to tumor cells grown in hollow fibers.³ Neil H. Riordan, PA-C, and colleagues,⁴ reported that vitamin C infusions of 60 g resulted in brief blood level elevations to 24 mM. Blood levels are only elevated 0.2 mM when vitamin C is given orally. In the CTCA study, the first cohort of 3 patients is being treated with 30 g/m²—approximately 50 g for an average-sized individual—vitamin C infusions on 4 consecutive days per week for a period of 4 weeks. 

Doses of vitamin C will be increased incrementally in future cohorts until the maximum tolerated dose is reached. Our goal is to have six dose escalations involving 18 patients. We are attempting to determine the safety, tolerability, optimum therapeutic dose, and pharmacokinetic profile of intravenous vitamin C, in addition to evaluating patient quality of life during treatment. We will also assess patients' tumor burden for preliminary indications of intravenous vitamin C anticancer activity. Information from this study may provide the basis for a phase 2 trial of intravenous vitamin C. 

The phase 1 clinical trial is open for accrual. As of February, 3 patients in the first cohort had completed their 4-week series of vitamin C infusions. One of these patients, whose disease was in stable condition, wanted to continue the vitamin C infusions and is currently on a continuation protocol. We are actively recruiting the second cohort of 6 patients. The current study should resolve some critical unanswered questions about the efficacy of vitamin C in cancer care. 

We will keep the osteopathic medical community informed as the study progresses during the next year. We also welcome readers' comments and insights.