Researchers at the Dana-Farber Cancer Institute and the Harvard School of Public Health published a study in the June 20 Journal of Clinical Oncology suggesting a link between high levels of vitamin D and increased colon cancer survival.
Kimmie Ng, M.D., lead author of the study, says, “There has been a lot of laboratory scientific evidence that vitamin D is involved in cell growth and can inhibit or slow down cancer cell growth in animal models. There are also epidemiologic studies that look at vitamin D levels and the risk of getting colon cancer, and they found that higher levels conferred a lower risk of getting colon cancer.”
However, Dr. Ng indicates there was not a lot of data published on how vitamin D levels related to how patients did after they were diagnosed with colon cancer, which was why they conducted the study. Dr. Ng and her fellow researchers identified patients from long-running cohort studies at Harvard, the Nurses’ Health Study and the Health Professionals Follow-up Study.
Dr. Ng says, “We looked at 304 participants in these studies who had their blood drawn and who also had a diagnosis of colon cancer. We assayed their blood for vitamin D levels and divided their levels into quartiles. We then compared the highest 25% to the lowest 25%. What we found was that people who had the levels in the highest 25% had 48% less risk of dying from colon cancer.”
During the study period, which ended in 2005, 123 patients died, 96 of them from colon or rectal cancer. The odds of dying from colon cancer specifically, according to the study, were 39% lower if the patient’s vitamin D levels were in the highest quartile, or 25%. Ng says, “It is significant. There’s definitely an association, which is what we showed in our study. I think definitive proof of the benefit would require vitamin D be studied in a clinical trial.”
Dr. Ng notes that a large national clinical trial is currently being planned for patients who have had their colon cancer removed by surgery. “The standard of care is usually to administer chemotherapy after surgery. We’re going to see if adding vitamin D has additional benefits on top of standard treatments for that group of patients.” They are also replicating the current study in a different cohort of patients to confirm the results.
Vitamin D, in the laboratory, seems to slow cancer cell growth, appears to be involved in programmed cell death, which can kill cancer cells, and may be involved in inhibiting blood vessel growth in tumors. Dr. Ng says, “There are multiple different biological mechanisms by which it could possibly be working in colon cancer. I think the take-home point is that higher vitamin D levels may be associated with better survival among people with colon cancer and further study of vitamin D is definitely needed.”