283PPrevalence of vitamin D3 deficiency among women with early breast cancer receiving chemotherapy in an oncology dayward

Abstract Background The Irish Longitudinal Study on Ageing (TILDA) estimates that 13.1% of the Irish population is vitamin D3 deficient, compared with less than 6% of the US population surveyed in the National Health and Nutrition Examination Survey (NHANES). In recent years, numerous studies have shed light on a potential role for vitamin D3 in breast cancer risk modification and prognosis. We set out to assess the prevalence and clinical significance of vitamin D3 deficiency in women with breast cancer receiving chemotherapy in an Irish oncology dayward. Methods Retrospective chart review was conducted to collect data incuding patient age, cancer stage at diagnosis, date of treatment initiation and 25-hydroxy vitamin D3 (25(OH)D3) levels at start of treatment. Vitamin D3 deficiency was defined as a value Results 41 women had available baseline 25(OH)D3 levels and were included. 66% were deficient in 25(OH)D3 at baseline. The prevalence of vitamin D3 deficiency showed substantial seasonal variation, being highest in the winter months (88%) and lowest in the summer months (0%). Furthermore, mean 25(OH)D3 levels were lowest in the winter months (29.0nmol/L + 13.8) and highest in the summer months (66.3nmol/L + 11.5). The difference in mean 25(OH)D3 levels across the four seasons was significant (p = 0.022). Women who were deficient in vitamin D3 tended to be younger (p = 0.00001), have a higher cancer stage (p = 0.0071), and have a less favorable 10-year all cause mortality risk as indicated by their CCI (p = 0.0041). Conclusions We found a striking prevalence of 25(OH)D3 deficiency among women with breast cancer receiving adjuvant/neoadjuvant chemotherapy in an Irish oncology dayward. Notable seasonal variation in mean vitamin D3 levels was observed. Vitamin D3 deficiency was found to be more prevalent in younger women and was associated with a higher stage of breast cancer as well as a less favorable 10-year all cause mortality risk. Legal entity responsible for the study the authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.