The new study, published in Anticancer Research, investigated a possible relationship between vitamin D levels (measured as 25-hydroxyvitamin D) and breast cancer survival rates after previous research suggested that low vitamin D status may be linked to a higher risk of premenopausal breast cancer.
Led by Professor Cedric Garland from the University of California, San Diego School of Medicine, the researchers performed a meta-analysis of five clinical studies, with data from more than, 4,000 breast cancer patients. They found that those with the highest vitamin D status had around twice the survival rate of those with the lowest status.
"The study has implications for including vitamin D as an adjuvant to conventional breast cancer therapy," explained co-author Heather Hofflich.
Indeed, Garland recommended that randomised controlled clinical trials to confirm their findings should commence soon - adding that it could be that adding vitamin D into a breast cancer patient's standard care could commence right away, so long as those patients were closely monitored.
"There is no compelling reason to wait for further studies to incorporate vitamin D supplements into standard care regimens since a safe dose of vitamin D needed to achieve high serum levels above 30 nanograms per milliliter has already been established," commented Garland.
Garland and colleagues performed the statistical analysis of five studies of 25-hydroxyvitamin D obtained at the time of patient diagnosis and their follow-up for an average of nine years.
When combined, the data included 4,443 breast cancer patients, said the team - who found that women classified in the 'high' serum group had an average level of 30 nanograms per milliliter (ng/ml) of 25-hydroxyvitamin D in their blood, while the 'low' group averaged 17 ng/ml.
The team noted that previous research has found the average vitamin D serum level in patients with breast cancer in the United States to be around 17 ng/ml.
"Higher serum concentrations of 25(OH)D were associated with lower case-fatality rates after diagnosis of breast cancer," explained the researchers. "Specifically, patients in the highest quintile of 25(OH)D had approximately half the death rate from breast cancer as those in the lowest."
Indeed, Garland and his team concluded that a high serum 25(OH)D status is associated with lower mortality from breast cancer.
"Serum 25(OH)D in all patients with breast cancer should be restored to the normal range (30-80 ng/ml), with appropriate monitoring," they wrote - adding that clinical studies should be initiated to confirm that this association was not due to reverse causation.
Source: Anticancer Research
Volume 34, Number 3, Pages 1163-1166. Full Study Here.
"Meta-analysis of Vitamin D Sufficiency for Improving Survival of Patients with Breast Cancer"
Authors: Sharif B. Mohr, Edward D. Gorham, et al