3889

Epidemiology of Cancer Survivorship

Low serum 25(OH)D levels in breast cancer patients with the aggressive basal-like phenotype

Tuesday, Apr 15, 2008, 8:00 AM -12:00 PM

Exhibit Hall B-F, San Diego Convention Center

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Christa Rainville, Yasir Khan, Mercedita Ramos, Glenn Tisman. A Medical Corporation, Whittier, CA

Studies have shown that breast cancer incidence, mortality and survival rates are inversely correlated with solar UVB irradiance and/or serum vitamin D levels. Our study sought to confirm vitamin D insufficiency in newly diagnosed breast cancer patients presenting for adjuvant therapy and to uncover possible relationships between serum 25(OH)D within the breast cancer phenotypes. We measured 89 breast cancer patients’ serum vitamin D level as 25(OH)D prior to adjuvant chemotherapy and/or hormone therapy. Four groups of breast cancer have been generally identified based on immunohistochemical and FISH analysis to determine estrogen receptor (ER), progesterone receptor (PR) and HER2 status. Our patients were classified as: luminal A (ER+ &/or PR+ and HER2-), luminal B (ER+ &/or PR+ and HER2+), basal-like (ER-, PR- and HER2-), HER2+/ER- (ER-, PR- and HER2+) and were staged according to the 2002 AJCC as either Early (stage I & II) or Advanced (stage III & IV). There is some variation as to how investigators define these breast cancer subtypes, but most agree that tumors negative for the three markers ER, PR and HER2 (triple negative) belong in the basal-like subgroup. We used unpaired t-test with significance level, a, of 0.05 (one tailed) to determine whether vitamin D levels were low in breast cancer patients as a whole and to investigate if variations in vitamin D status between the breast cancer phenotypes. The mean serum 25(OH)D levels for all phenotypes except for HER2+/ER- were lower than the lower mean limit of normal (<80 nmol/L). Patients with basal-like breast cancer exhibited lower mean 25(OH)D levels than the HER2+/ER-, luminal A and luminal B subtypes. The mean +/- standard deviation for serum vitamin D levels were as follows: luminal A (79.4 +/- 53.7 nmol/L, n=65), luminal B (74.9 +/- nmol/L 27.4, n=6), basal-like (54.1 +/- 19.0 nmol/L, n=13), and HER2+/ER- (92.9 +/- 25.7 nmol/L, n=5). The t-test showed that 25(OH)D levels were significantly lower in patients with basal-like than HER2+/ER- (p<0.02) and luminal A (p<0.01). However, distinction could not be made for comparison between basal-like and luminal B (0. 10 > p > 0.05). Tumor stage was not associated with 25(OH)D levels. Our results confirmed the previous findings that most patients presenting for adjuvant therapy for breast cancer are deficient in vitamin D (Plant, AS & Tisman, G. Nutrition and Cancer 56(2): 143-148, 2006). We also found that one of the most aggressive breast cancer subtypes, basal-like, was associated with the lowest baseline serum vitamin D level. Our data supports the idea that low serum levels of 25(OH)D may contribute to a higher prevalence of the basal-like breast cancer phenotype. Further studies are warranted to investigate possible relationships between tumor types, pathological grades, clinical stages, overall and cancer specific survival and vitamin D sufficiency.