De novo vitamin D supplement use post-diagnosis is associated with breast cancer survival

Breast Cancer Res Treat. 2018 Nov;172(1):179-190. doi: 10.1007/s10549-018-4896-6. Epub 2018 Jul 23.


Purpose: Experimental laboratory data have indicated a protective effect of vitamin D on breast cancer progression, while epidemiological evidence is growing. Using pharmacy claims data, this study investigates the association between vitamin D supplement use initiated after a breast cancer diagnosis and associated mortality.

Methods: Women aged 50-80 years with a record of invasive breast cancer were identified on the National Cancer Registry Ireland database (n = 5417). Initiation of de novo vitamin D post-diagnosis was identified from linked national prescription data (n = 2581, 49%). Multivariate Cox proportional hazards models were used to estimate adjusted HRs (95% CIs) for breast cancer-specific mortality.

Results: There was a 20% reduction in breast cancer-specific mortality in de novo vitamin D users (modelled as a time-varying variable) compared to non-users (HR 0.80; 95% CI 0.64-0.99, p = 0.048) and the reduction was greater at 49% (HR 0.51; 95% CI 0.34-0.74, p < 0.001), if vitamin D was initiated soon after the breast cancer diagnosis (within 6 months).

Conclusions: In this large national breast cancer cohort, de novo vitamin D use post-diagnosis was found to be associated with a reduction in breast cancer-specific mortality. Vitamin D, therefore, has the potential as a non-toxic and inexpensive agent to improve survival in breast cancer patients. Findings support the need for RCTs exploring the effect of vitamin D supplementation on breast cancer survival.

Keywords: Breast cancer mortality; Prognosis; Supplement use; Vitamin D.

MeSH terms

  • Aged
  • Aged, 80 and over
  • Breast / abnormalities
  • Breast / pathology
  • Breast Neoplasms / diet therapy*
  • Breast Neoplasms / epidemiology
  • Breast Neoplasms / pathology
  • Cancer Survivors*
  • Dietary Supplements*
  • Female
  • Humans
  • Hypertrophy / diet therapy
  • Hypertrophy / epidemiology
  • Hypertrophy / pathology
  • Ireland / epidemiology
  • Middle Aged
  • Proportional Hazards Models
  • Vitamin D / therapeutic use*


  • Vitamin D

Supplementary concepts

  • Gigantomastia