Patients with breast cancer who had higher levels of vitamin D in their blood at diagnosis tended to have better outcomes, according to a recent study.
Higher levels of vitamin D improved overall survival (OS) for some women with breast cancer, according to a study conducted by researchers at Roswell Park Cancer Institute and Kaiser Permanente Northern California and published online by JAMA Oncology.
Researchers found that women with the highest levels of vitamin D experienced a 30 percent increase in OS. Premenopausal women with higher vitamin D levels also had 48 percent better recurrence-free survival and 63 percent better breast cancer-specific survival.
More than 1,600 women participating in the Pathways Study, a group of women with breast cancer established at Kaiser Permanente Northern California, were examined over seven years. Researchers focused on prognosis and outcomes. In addition, they documented the 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, Ph.D., associate professor of Oncology in the department of cancer prevention and control at Roswell Park and first author on the study, in an interview with CURE. “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.”
Baseline interviews were conducted in person and included detailed questionnaires. Blood samples were also obtained. Then, regular follow-ups were conducted via mailed or telephone questionnaires for lifestyle factors at six, 24 and 72 months. Health outcomes and comorbidities follow-ups were done at 12, 24, 48, 72 and 96 months. Blood samples were collected at a median of 69 days after diagnosis.
In the study, higher blood biomarker of Vitamin D — 25-hydroxyvitamin D (250HD) levels were associated with better OS. The association of higher blood levels of 250HD and OS was also stronger in premenopausal women.
The study reported lower 250HD blood concentrations in women with advanced-stage tumors and the lowest 250HD concentrations in premenopausal women with triple-negative cancer.
“Here we are looking at survival and we tried to look at menopausal status because premenopausal and postmenopausal breast cancer are 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.