Dec. 14, 2010 (San Antonio) -- Women with breast cancer who take multivitamins with minerals appear to face lower odds of having their cancer come back or dying.
"Multivitamins appears to especially benefit women undergoing radiation treatment," says researcher Heather Greenlee, ND, PhD, of Columbia University's Herbert Irving Comprehensive Cancer Center in New York City.
The study doesn't prove cause and effect. The association could be explained by other factors, such as the fact that women who eat right and exercise regularly are more likely to take vitamins, agree Greenlee and Edith Perez, MD, director of the breast cancer program at the Mayo Clinic in Jacksonville, Fla.
Still, the findings set the stage for a trial called Pathways, which will enroll about 4,500 women with breast cancer and follow them over time to see how lifestyle factors, including diet and supplement use, influence breast cancer recurrence and death.
Women With Breast Cancer More Likely to Take Vitamins
About 60% of women with breast cancer take multivitamins, compared with 38% of healthy women, Greenlee tells WebMD. Yet no studies have examined the association between multivitamin use and breast cancer prognosis, according to Greenlee.
So she and colleagues at Kaiser Permanente Northern California studied 2,239 women diagnosed with early-stage breast cancer between 1997 and 2000.
Forty-four percent took multivitamins with minerals and 13% took multivitamins without minerals at least three times a week for 12 months or more in the three years prior to diagnosis. After diagnosis, 65% and 19% reported using multivitamins with and without minerals, respectively.
By May 2010, 363 of the women relapsed and 372 died, 202 from breast cancer.
Taking Multivitamins With Minerals May Lower Risk of Breast Cancer Coming Back
Among the findings, presented at the San Antonio Breast Cancer Symposium:
Compared with women who never took multivitamins with minerals, women who took them anytime after diagnosis were 29% less likely to have a recurrence and 22% less likely to die from breast cancer.
Women who took multivitamins with minerals before diagnosis and at least three times a week for a year or more after diagnosis were 31% less likely to relapse and 27% less likely to die from breast cancer, compared with those who never took them.
When the results were stratified by treatment type, women who underwent radiation treatment benefited the most.
Greenlee says that women who took multivitamins with minerals six or seven days a week after diagnosis appeared to have the lowest risk of recurrence and death.
Women who took them for 12 months or more appeared to have a lower risk of recurrence, but not of dying from breast cancer, compared with women who took them less frequently.
Taking multivitamins without minerals did not appear to be protective, but that analysis was limited by the small number of women who took them, Greenlee says.
"There was no suggestion of harm from the supplements," she says.
Previous studies of multivitamins and cancer have had conflicting results.
This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.