Women with breast cancer who have sufficient vitamin D levels have improved survival outcomes compared to those with vitamin D deficiency, according to research published in the Journal of the National Comprehensive Cancer Network.
Patients with sufficient levels of vitamin D also have a lower incidence of cardiometabolic risk factors than those without sufficient levels, study researchers reported.
In this analysis, the researchers used data from the Pathways Study, an ongoing prospective study involving 4504 women with newly diagnosed incident invasive breast cancer from Kaiser Permanente Northern California. The women were enrolled in the study between 2006 and 2013 and within 2 months of diagnosis. The later Pathways Heart Study included participants from the Pathways Study.
All participants completed an in-person baseline questionnaire on a wide range of epidemiologic factors relevant to breast cancer survivorship, and blood samples were collected from approximately 90% of participants at a median of 69 days after diagnosis, with 30% of samples obtained after the initiation of chemotherapy. Serum samples from 3995 participants were analyzed for total 25-hydroxyvitamin D (25OHD) concentrations.
The average age of the participants at diagnosis was 59.6 years. Women aged 60 years or older and those reporting vitamin D supplementation had higher 25OHD concentrations. A higher body mass index (BMI), non-Hispanic Black race/ethnicity, lower physical activity, current smoking, lower educational attainment, being single, being disabled, being unemployed, and having full-time employment were all linked to lower vitamin D concentrations.
Vitamin D deficiency, defined as less than 20.0 ng/mL, was identified in 38% of women, and 25% were deemed to have sufficient vitamin D levels (≥30.0 ng/mL).
Multivariate Cox hazards models adjusted for a range of potential confounding factors showed that, compared to women with vitamin D deficiency, those with sufficient vitamin D levels had significantly greater overall survival (hazard ratio [HR], 0.76; 95% CI, 0.62-0.93; P =.005), as well as better second primary cancer-free survival (HR, 0.75; 95% CI, 0.63-0.90; P =.003) and disease-free survival (HR, 0.82; 95% CI, 0.70-0.97; P =.05).
The strongest association between vitamin D levels and survival outcomes was seen in stage II or higher advanced disease, the researchers reported (P for interaction ≤.02). No significant differences were seen when the researchers stratified by tumor endocrine receptor status or BMI (P for interaction >.05).
Further analysis revealed that sufficient vitamin D levels were associated with a reduced risk of incident cardiometabolic risk factors, diabetes, and dyslipidemia, even after adjustment. The strongest association was with cardiometabolic risk factors, at an HR of 0.67 for women with sufficient levels compared to those without (95% CI, 0.54-0.83; P <.001). However, there was no significant association between vitamin D levels and cardiovascular disease-related death.
“With no [randomized controlled trials] on vitamin D supplementation in patients with breast cancer expected in the near future, our findings provide strong observational evidence supporting multiple extraskeletal benefits of maintaining vitamin D sufficiency after diagnosis,” the researchers concluded.
They added, “Routine screening for vitamin D deficiency in this patient population may be advisable, with correction through daily supplementation when clinically indicated — not only for the benefits of bone health, but also to potentially improve cancer prognosis and cardiometabolic health.”
Barbara Jacoby is an award winning blogger that has contributed her writings to multiple online publications that have touched readers worldwide.