High vitamin D levels increase survival of patients with metastatic colorectal cancer

The research, based on data from more than 1,000 patients with metastatic colorectal cancer who enrolled in a phase 3 clinical trial of chemotherapy plus biologic therapies, adds to vitamin D's already impressive luster as a potential cancer-inhibiting agent. In the study, patients with the highest blood levels of vitamin D survived for a median period of 32.6 months, compared to 24.5 months for those with the lowest levels.

"This is the largest study that has been undertaken of metastatic colorectal cancer patients and vitamin D," said the study's lead author, Kimmie Ng, MD, MPH, a medical oncologist at Dana-Farber. "It's further supportive of the potential benefits of maintaining sufficient levels of vitamin D in improving patient survival times."

The study didn't examine whether there is a biological cause-and-effect relationship between higher vitamin D levels and extended survival. As a result, researchers said, it's too early to recommend vitamin D as a treatment for colon cancer. Ng and colleagues at Dana-Farber are conducting clinical trials to further investigate whether vitamin D supplementation is useful in treating the cancer.

In the study, researchers measured blood levels of 25-hydroxyvitamin D, a substance produced in the liver from vitamin D, in 1,043 patients when they enrolled in a phase 3 trial of three different drug combinations for newly diagnosed, advanced colorectal cancer. Patient vitamin D levels ranged from an average of 8 nanograms/milliliter (ng/mL) in the lowest group to an average of 27.5 ng/mL in the highest group. The average level in all the patients was 17.2 ng/mL. Current practice guidelines from the Endocrine Society define vitamin D deficiency as having less than 20 ng/mL.

Researchers divided the patients into five groups based on vitamin D levels. On average, those with the highest levels survived 33 percent longer than those with the lowest (32.6 months vs. 24.5 months). Higher vitamin D levels were also associated with longer time to disease progression (12.2 months vs. 10.1 months).

Because high vitamin D levels can be a reflection of a healthy lifestyle (good nutrition, plenty of outdoor physical activity), researchers controlled for factors such as diet, obesity, and level of physical activity. Even then, the relationship between elevated vitamin D levels and extended survival held firm, Ng observed.