Song Yao, PhD
Women with breast cancer who have higher levels of vitamin D in their blood at diagnosis have a better prognosis, and the benefit is especially prominent among premenopausal women, according to findings of a large, prospective observational study of breast cancer survivors.
Researchers found that women with the highest levels of vitamin D at diagnosis experienced a 30% increase in overall survival (OS). Premenopausal women with higher vitamin D levels also had 48% better recurrence-free survival and 63% better breast cancer–specific survival.
The Pathways Study involved 1666 participants diagnosed with incident invasive breast cancer from 2006 to 2013 and was led by researchers at Roswell Park Cancer Institute and Kaiser Permanente Northern California.
Study participants were a mean age of 58.7 years and followed for health outcomes and comorbidities at several intervals over an average of 7 years, with a focus on frequency of breast cancer recurrence, second primary cancer, and death.
“The major strength of this study is the patient population we had,” said Song Yao, PhD, in an interview with Oncology Nursing News
. Yao is an associate professor of oncology in the Department of Cancer Prevention and Control at Roswell Park and first author on the study.
“At the beginning of the study, every patient was just diagnosed and then we followed them for a long time, so this type of design has some strength. Because of this wonderful population, we have findings that are more convincing, and there are some previous smaller studies that the findings are consistent with.”
For the study blood samples were collected, and baseline interviews were conducted in person and with detailed questionnaires. Higher biomarker blood levels of Vitamin D – 25-hydroxyvitamin D (250HD) were associated with better OS. Lower 250HD blood concentrations were seen in women with advanced-stage tumors and the lowest were found to be in premenopausal women with triple-negative cancer.
“We looked at menopausal status because premenopausal and postmenopausal breast cancer is quite different in regards to etiology and treatment options,” said Yao. “We found stronger association among premenopausal women, but actually we don’t have very clear knowledge of why that is the case.”
The study’s findings were adjusted for contributing factors that include age, obesity and ethnicity, as well as socioeconomic status, exercise, smoking, the season of blood collection and tumor characteristics.
“Our study adds to the evidence that may be important in improving breast cancer survival, but we have to be cautious because our study is not a clinical trial,” said Yao.
He recommends that patients with breast cancer and their caregivers stick to recommendations provided by their physician.
Yao adds that further research is needed for a clearer understanding of associations between vitamin D levels and risk of breast cancer progression and death.
Yao S, Kwan ML, Ergas IJ, et al. Association of serum level of vitamin d at diagnosis with breast cancer survival: a case-cohort analysis in the pathways study [published online ahead of print November 10, 2016]. JAMA Oncol.