title: Serum vitamin D levels and survival of patients with colorectal cancer: post-hoc analysis of a prospective cohort study.
abstract: BACKGROUND
  Recently, 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  Serum 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).
  
  
  CONCLUSIONS
  These results suggest that higher 25OHD levels at surgery may be associated with a better survival rate of patients with colorectal cancer.
authors.affiliation: Division of Molecular Epidemiology, Jikei University School of Medicine, Nishi-shimbashi, Minato-ku, Tokyo, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Mezawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sugiura
authors.forename: Michiaki
authors.initials: M
authors.lastname: Watanabe
authors.forename: Chihiro
authors.initials: C
authors.lastname: Norizoe
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takahashi
authors.forename: Akira
authors.initials: A
authors.lastname: Shimojima
authors.forename: Seryna
authors.initials: S
authors.lastname: Tamez
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsutsumi
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yanaga
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Urashima
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000097:blood* / Q000401:mortality* / Q000601:surgery; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015996:Survival Rate; D016896:Treatment Outcome; D014807:Vitamin D / Q000097:blood*
chemical_list: D014807:Vitamin D