Vitamin C Shows a Survival Signal in Early Blood Cancers—but There’s a Catch

A common vitamin has produced an unexpected survival signal in people living with precancerous blood disorders and early-stage blood cancers. In the phase 2 EVITA trial, patients taking a daily vitamin C supplement experienced fewer serious complications, while a follow-up analysis found substantially fewer deaths than in the placebo group. The results are detailed in new findings on vitamin C and cancer survival.

EVITA enrolled 109 adults in Denmark and the United States with clonal cytopenia of undetermined significance, or CCUS, and lower-risk myeloid malignancies including myelodysplastic syndrome. These conditions can remain stable, but they may also progress toward acute myeloid leukemia, an aggressive cancer that can be difficult to treat. Participants were randomly assigned to receive either 1,000 milligrams of oral vitamin C each day or a matching placebo for 12 months.

The study was designed to test whether vitamin C could slow the expansion of abnormal blood-cell clones. It did not meet that primary goal: the rate of clonal growth was not meaningfully different between the two groups. That result is important because it means the supplement was not shown to halt the underlying disease process, even though researchers observed other potentially meaningful changes, including shifts in inflammatory signaling.

The more surprising result emerged during longer follow-up. After a median of 33.6 months, 11 people in the vitamin C group had died compared with 24 in the placebo group. Serious adverse events were also less common among participants receiving vitamin C—18 of 55 patients versus 30 of 53 in the placebo arm—although gastrointestinal problems occurred more often among those taking the supplement.

Researchers are treating the survival finding as exploratory rather than definitive. The trial was relatively small, and survival was not the primary endpoint, so the apparent advantage could reflect factors that a larger study would clarify. The investigators say a phase 3 trial is needed before vitamin C can be considered an established strategy for preventing complications or improving survival in CCUS and low-risk myeloid cancers.

The results also add nuance to a long-running debate over vitamin C and cancer. Earlier studies using high-dose vitamin C pills did not show a clear benefit for advanced colorectal cancer, while research into intravenous vitamin C has followed a different line because blood concentrations can be much higher. EVITA instead tested a comparatively straightforward oral supplement in patients who were not receiving anticancer therapy, making its safety and follow-up findings potentially relevant to a difficult period when doctors often monitor disease rather than immediately begin treatment.

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Vitamin supplement pills via Wikimedia Commons by Raysonho @ Open Grid Scheduler / Grid Engine with usage type - Creative Commons License. By Raysonho @ Open Grid Scheduler / Grid Engine - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=45183927