A prospective analysis of data from a phase III study of patients with newly diagnosed metastatic colorectal cancer indicates that patients with higher vitamin D levels have better outcomes after treatment with chemotherapy and targeted therapy. This study was presented at the 2015 Gastrointestinal Cancers Symposium in San Francisco, California.

The median overall survival for patients with the highest vitamin D levels was 32.6 months, compared with 24.5 months for patients with the lowest levels.

This study adds to growing evidence of the antitumor effects of vitamin D that have been observed in preclinical and epidemiologic research. Randomized studies are underway to confirm the value of taking vitamin D supplements before and after cancer diagnosis.

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“Our study adds to the body of research showing that higher vitamin D levels are associated with significantly improved survival. The ultimate goal is to translate this research into an effective intervention for patients by conducting randomized trials of vitamin D supplementation for treatment of colorectal cancer,” said lead study author Kimmie Ng, MD, MPH, assistant professor of medicine at Dana-Farber Cancer Institute, Harvard Medical School in Boston, Massachusetts.

“It is too early to recommend vitamin D as a treatment for colon cancer, but we do know that maintaining adequate vitamin D levels has other health benefits, such as for bone health.”

Researchers measured blood levels of vitamin D (25-hydroxyvitamin D) in 1,043 patients at the time they were enrolled in CALGB 80405, a phase III trial comparing three different first-line treatments for newly diagnosed, advanced colorectal cancer (chemotherapy plus bevacizumab, cetuximab, or bevacizumab and cetuximab).

Patient vitamin D levels ranged from an average of 8 ng/mL in the lowest group to an average of 27.5 ng/mL in the highest group, with the average in all patients being 17.2 ng/mL (the recommended healthy range is 20-30 ng/mL).

Older age, black race, lower dietary and supplemental vitamin D intake, higher body-mass index (BMI), worse general physical condition, and lower physical activity were all associated with lower vitamin D levels.

Patients whose blood specimens were drawn in the winter and spring months also had significantly lower vitamin D levels, as did patients who resided in the Northern and Northeastern parts of the United States. All these factors have previously been found to be linked to lower vitamin D levels. Overall, very few of the patients reported vitamin D supplement use.

For the purpose of analysis, patients were divided into five groups based on vitamin D levels. After adjusting for prognostic factors and healthy behavior, researchers found that patients in the group with the highest levels of vitamin D lived significantly longer (32.6 months on average), compared with those in the group with the lowest levels (24.5 months on average).

Higher vitamin D levels were also associated with longer time to disease progression (12.2 months in the group with the highest levels vs. 10.1 months in the group with the lowest). No significant differences were seen with regard to the type of therapy the patients received.

Ng indicated that ongoing clinical trials are exploring the potential impact of vitamin D supplementation on cancer prevention and treatment.

This study received funding from The National Cancer Institute.