Posted: Dec 14, 2010 11:10 PM
"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 others factors, such as the fact that women who eat right and exercise regularly are more likely to take vitamins, says 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 Pathway, which will enroll 4,500 women diagnosed with breast cancer. Half will be given multivitamins with minerals and half won't, and all will be followed for years to see how many in each group have their cancer recur or die. The study is just starting to recruit women, Greenlee says.
About 60% of women with breast cancer take multivitamins, compared with 38% of healthy women, she tells WebMD.
Yet no studies have examined the association between multivitamin use and breast cancer prognosis, according to the Greenlee.
So she and colleagues combed the medical records of 2,239 women diagnosed with early-stage breast cancer between 1997 and 2000.
A total of 44% 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.
Among the findings, presented at the San Antonio Breast Cancer Symposium:
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.