Abstract
BackgroundRecently, serum 25-hydroxyvitamin D (25OHD) levels were shown to be associated with the survival of patients with colorectal cancer. However, 25OHD levels were measured a median of 6 years before diagnosis or were predicted levels. In this study, we directly measured serum 25OHD levels at surgery and examined the association with survival among patients with colorectal cancer.MethodsWe started a prospective cohort study to find prognostic factors in patients with colorectal cancer from 2003 to 2008 and stored serum samples and clinical data. As part of a post-hoc analysis, serum 25OHD levels were measured by radioimmunoassay. Association between overall survival and serum 25OHD levels were computed using the Cox proportional hazard model adjusted for month of serum sampling as well as age at diagnosis, gender, cancer stage, residual tumor after surgery, time period of surgery, location of tumor, adjuvant chemotherapy and number of lymph nodes with metastasis at surgery. Unadjusted and adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) were determined.ResultsSerum 25OHD levels were measured in 257 patients. Only 3% had sufficient levels (30 ng/ml and greater). Based on month of blood sampling, an annual oscillation of 25OHD levels was seen, with levels being lower in spring and higher in late summer. Higher 25OHD levels were associated with better overall survival under multi-variate analysis (HR, 0.91: 95% CI, 0.84 to 0.99, P = 0.027).ConclusionsThese results suggest that higher 25OHD levels at surgery may be associated with a better survival rate of patients with colorectal cancer.
Highlights
Serum 25-hydroxyvitamin D (25OHD) levels were shown to be associated with the survival of patients with colorectal cancer
Because vitamin D is made under the skin by exposure to ultraviolet-B radiation in sunlight, low levels of serum vitamin D may contribute to a higher risk of morbidity and mortality associated with colon cancer [3]
Ng et al demonstrated that higher pre-diagnosis blood 25OHD levels were associated with a significant improvement in overall survival of patients with colorectal cancer [13]
Summary
Serum 25-hydroxyvitamin D (25OHD) levels were shown to be associated with the survival of patients with colorectal cancer. Ng et al demonstrated that higher pre-diagnosis blood 25OHD levels were associated with a significant improvement in overall survival of patients with colorectal cancer [13]. They only had a single measurement of plasma 25OHD levels taken a median of 6 years before diagnosis. They calculated post-diagnosis 25OHD levels using race, geographic region, and baseline values of physical activity, body mass index, and vitamin D intake reported 1 to 4 years after colorectal cancer diagnosis according to Giovannucci's method [14]. For a more accurate portrayal of 25OHD levels, we collected blood samples at surgery, measured 25OHD levels directly, and investigated the relationship between individual serum levels of 25OHD and overall survival in patients diagnosed with colorectal cancer, according to the vitamin D hypothesis [3]
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