Patients diagnosed with colon cancer who had abundant vitamin D in their blood were less likely to die during a follow-up period than those who were deficient in the vitamin, according to a new study published in the June 20 issue of the Journal of Clinical Oncology.
The findings of the study merit further research, but it is too early to recommend supplements as a part of treatment, state the investigators from Dana-Farber Cancer Institute and the Harvard School of Public Health.
Previous research has shown that higher levels of vitamin D reduce the risk of developing colon and rectal cancer by about 50%, but the effect on outcomes wasn’t known. To examine this question, the investigators, led by Kimmie Ng, M.D., and Charles Fuchs, M.D., of Dana-Farber, analyzed data from two long-running epidemiologic studies whose participants gave blood samples and whose health has been monitored for many years.
They identified 304 participants in the Nurses’ Health Study and the Health Professionals Followup Study who were diagnosed with colorectal cancer between 1991 and 2002. All had vitamin D levels measured in blood samples given at least two year prior to their diagnosis. Each patient’s vitamin D measurement was ranked by quartiles. Those whose levels were in the lowest quartile were considered deficient in vitamin D.
The researchers followed the 304 patients until they died or until 2005, whichever occurred first. During that period, 123 patients died, with 96 of them dying from colon or rectal cancer. The researchers then looked for associations between the patients’ previously measured vitamin D blood levels and whether they had died or survived.
The results showed that individuals with the vitamin D levels in the highest quartile were 48% less likely to die (from any cause, including colon cancer) than those with the lowest vitamin D measurements. The odds of dying from colon cancer specifically were 39% lower, the scientists found.
“Our data suggest that higher prediagnosis plasma levels [of vitamin D] after a diagnosis of colorectal cancer may significantly improve overall survival,” the authors wrote. “Future trials should examine the role of vitamin D supplementation in patients with colorectal cancer.”
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