Prospective Study of Vitamin D Levels in Sydney Patients with a New Diagnosis of Breast Cancer.

Abstract

Abstract Background: Vitamin D deficiency has been associated with malignancy in many reported studies. More recently an association has emerged between low levels of vitamin D and poorer outcome in breast cancer. Australian recommendations for vitamin D are defined as deficient if 25-OH vitamin D levels are ≤ 50nmol/L and severely deficient if ≤12.5nmol/L. We hypothesise that lower levels of vitamin D are associated with a more advanced disease at diagnosis.Methods: We conducted a prospective study in patients with a new diagnosis of breast cancer who presented to our area health service from January 1st 2008 to October 1st 2008. Patients were also included if their diagnosis occurred in the preceding 6 months and were referred onto the multidisciplinary breast care team for treatment in this time period. 25-OH vitamin D levels were measured for each patient during staging and details collected about each patients breast cancer characteristics. Patients completed a questionnaire assessing comorbidities, medications, diet and lifestyle effects which were likely to influence vitamin D levels. We used stage, disease requiring chemotherapy, and the need for mastectomy as surrogate endpoints for assessing disease extent.Results: 166 patients were recruited with a median age of 58 (range 21-100). The median vitamin D level was 48 (range of <10 to 170). 53% (n=88) patient were deficient (25-OH vitamin D ≤ 50nmol/L), 2% (n=3) patients were severely deficient (25-OH vitamin D ≤ 12.5nmol/L) and only 14% had sufficient levels (25-OH vitamin D >75nmol/L). The majority of patients reported the recommended sun exposure during weekdays (77%) and on weekends (86%). Most were had fair or medium skin tones (83%) and less than 10% wore sunscreen daily. Only 22% of patients had a potential identifiable cause for vitamin D deficiency. Vitamin D levels did not correlate directly with stage of disease (RR 1.03, 95% CI 0.86-1.23 p=0.85), however other surrogates for more advanced disease including the need for more aggressive treatment either with chemotherapy (RR 1.30, 95% CI 1.05-1.61 p=0.02) or mastectomy (RR 1.67 95% CI 1.03-2.7 p=0.04) were associated with low levels of vitamin D.Conclusions: Vitamin D deficiency is very prevalent in our population of patients diagnosed with breast cancer, despite perceived adequate sun exposure and lack of obvious cause. Lower levels of vitamin D did not directly correlate with more advanced stage of the disease at diagnosis; however patients with low levels of vitamin D were more likely to need chemotherapy or require mastectomy, which may suggest a more aggressive disease. The cause of breast cancer remains multifactorial and vitamin D deficiency is only one part of this complex disease. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6071.