Colon Cancer Mortality Risk Drops as Vitamin D Levels Rise

By Charles Bankhead
BOSTON, 20 june 2008-- Mortality risk declined significantly in colon cancer patients who had higher vitamin D levels before diagnosis, investigators here reported.
Patients with the highest levels of plasma 25-hydroxyvitamin D3 (25[OH]D) had half the overall mortality risk of those with the lowest levels, Kimmie Ng, M.D., of Dana-Farber Cancer Institute, and colleagues reported in the June 20 issue of the Journal of Clinical Oncology.
Cancer-specific mortality was 40% lower in patients with the highest levels, but the difference did not reach statistical significance.
"Additional efforts to understand the mechanisms through which the vitamin D pathway influences colorectal carcinogenesis and cancer progression are warranted," Dr. Ng and colleagues concluded. "Moreover, future trials should examine the role of vitamin D supplementation in patients with colorectal cancer."
Higher plasma levels of (25[OH]D) are associated with a decreased risk of colorectal cancer. However, the influence of vitamin D levels on outcomes of colorectal cancer had not been examined previously.
Using data from the Nurses' Health Study and the Health Professional Follow-Up Study, the authors examined the relationship between prediagnosis 25(OH)D levels and colorectal cancer mortality.
The analysis included 304 study participants with newly diagnosed colorectal cancer from 1991 through 2002. Investigators excluded patients whose diagnoses occurred within two years of baseline blood collection.
Patients were observed until death, until June 2005 (in the Nurses' Health Study), or until January 2005 (in the Health Professionals Follow-Up Study), whichever came first. The primary outcome was overall mortality.
The patients were separated into quartiles of plasma 25(OH)D levels, which ranged from a mean of 16.5 ng/mL to a mean of 40 ng/mL. The authors found a significant trend for lower mortality as prediagnostic D levels increased (P=0.02).
Comparison of the highest and lowest quartiles resulted in an adjusted mortality hazard ratio of 0.52 in favor of the higher 25(OH)D quartile. Patients in the highest quartile had a 39% lower cancer-specific mortality compared with the lowest quartile (HR 0.61, 95% CI 0.31 to 1.19).
Exclusion of patients diagnosed within five years of blood collection did not appreciably alter the results (P=0.04 for trend). The multivariate hazard ratio for overall mortality was 0.45 (95% CI 0.19 to 1.09) for comparison of the highest and lowest 25(OH)D quartiles.
"The study by Ng et al is one of the first steps toward learning more about health behaviors that can affect colorectal cancer prognosis," Cornelia Ulrich, Ph.D., and Rebecca Holmes of the Fred Hutchinson Cancer Research Center in Seattle, said in an accompanying editorial.
However, the results do not answer the question of whether vitamin D supplementation should be recommended for patients with colon cancer or those at high risk. An ongoing trial of vitamin D and calcium supplementation in high-risk patients has the potential to provide an answer, the editorialists added.
Dr. Ng reported no disclosures, but coauthor Bruce W. Hollis disclosed a consultant/advisory relationship with DiaSorin Corp.
Drs Ulrich and Holmes reported no disclosures.
Primary source: Journal of Clinical OncologySource reference:Ng K, et al "Circulating 25-hydroxyvitamin D levels and survival in patients with colorectal cancer" J Clin Oncol 2008; 26: 2984-2991. Additional source: Journal of Clinical OncologySource reference: Ulrich CM, Holmes RS "Shedding light on colorectal cancer prognosis: vitamin D and beyond" J Clin Oncol 2008; 26: 2937-2939.