title: The effect of pre-diagnostic vitamin D supplementation on cancer survival in women: a cohort study within the UK Clinical Practice Research Datalink.
abstract: BACKGROUND
  There remains uncertainty in whether vitamin D status affects cancer survival. We investigated whether vitamin D (± calcium) supplementation affects cancer survival in women.
  
  
  METHODS
  Participants were women aged ≥55 years identified from the UK Clinical Practice Research Datalink (CPRD) with a first diagnosis of breast, colorectal, lung, ovarian or uterine cancer between 2002 and 2009, and at least 5 years of CPRD data prior to diagnosis. Cox proportional hazards were used to estimate hazard ratios (HR) and 95 % confidence intervals (CI) of the relationship between pre-diagnostic vitamin D supplementation and all-cause mortality. To avoid confounding by indication, the primary analysis compared women with 3+ to 1-2 (but no more) vitamin D prescriptions. Models were adjusted for pre-diagnostic body mass index, smoking, alcohol and deprivation. A sensitivity analysis excluded supplements prescribed in the year prior to diagnosis.
  
  
  RESULTS
  Exposure to 3 or more versus 1 to 2 prescriptions of vitamin D was not associated with survival from any of the cancers studied. Any vitamin D prescription, compared to never having been prescribed one, was associated with a better survival from breast cancer (HR 0.78, 95 % CI 0.70 to 0.88). The sensitivity analysis suggested a possible detrimental effect of vitamin D supplementation on lung cancer outcomes (HR for 3 versus 1 or 2 prescriptions 1.22 (95 % CI 0.94 to 1.57); HR for any versus no prescriptions 1.09 (0.98 to 1.22)).
  
  
  CONCLUSIONS
  We found no evidence that vitamin D supplementation is associated with survival among women with cancer. Previous observational findings of beneficial effects of vitamin D supplementation on cancer survival may be confounded.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK. Mona.Jeffreys@bristol.ac.uk.
authors.forename: Mona
authors.initials: M
authors.lastname: Jeffreys
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK. theresa.redaniel@bristol.ac.uk.|NIHR CLAHRC West, 9th Floor, Whitefriars, Lewins Mead, Bristol, BS1 2NT, UK. theresa.redaniel@bristol.ac.uk.
authors.forename: Maria Theresa
authors.initials: MT
authors.lastname: Redaniel
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, 39 Whatley Road, Bristol, BS8 2PS, UK. Richard.Martin@bristol.ac.uk.|Medical Research Council/University of Bristol Integrated Epidemiology Unit, University of Bristol, Bristol, UK. Richard.Martin@bristol.ac.uk.|University of Bristol/University Hospitals Bristol NHS Foundation Trust National Institute for Health Research Bristol Nutrition Biomedical Research Unit, University of Bristol, Bristol, UK. Richard.Martin@bristol.ac.uk.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Martin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002118:Calcium / Q000008:administration & dosage; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008875:Middle Aged; D009026:Mortality; D009369:Neoplasms / Q000453:epidemiology* / Q000401:mortality; D016016:Proportional Hazards Models; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage
chemical_list: D014807:Vitamin D; D002118:Calcium