Results of the Life After Cancer Epidemiology (LACE) study reported at the 2010 San Antonio Breast Cancer Symposium indicate that taking multivitamins with minerals may be beneficial in lowering a woman's risk of breast cancer recurrence and death. Breast cancer patients are more frequent users of multivitamins than healthy populations (approximately 60% compared to 38% in one large survey), yet no studies to date have examined the association between multivitamin use and prognosis.

The study included 2,240 women aged 18 to 70 who were patients of the Kaiser Permanente Northern California health care system and were diagnosed with nonmetastatic breast cancer between 1997 and 2000. The women entered the study two years post-diagnosis, on average. A mailed questionnaire was used to collect information on multivitamin use for five years before diagnosis and since breast cancer diagnosis, in addition to other lifestyle factors and demographic information. Tumor and treatment characteristics were determined using Kaiser Permanente Northern California Cancer Registry and clinical databases. Outcomes, including recurrence and death from any cause, were determined once per year using a mailed questionnaire and verified by medical record review. A total of 363 recurrences, 202 breast cancer deaths, and 372 deaths from all causes had occurred by May 7, 2010.

Forty-nine percent of study participants reported taking multivitamins with minerals before breast cancer diagnosis and 65% reported taking them after diagnosis. Thirteen percent and 19% of participants reported taking multivitamins without minerals pre- and post-diagnosis, respectively. Taking multivitamins with minerals after diagnosis was found to be associated with a 20% lower risk of recurrence and 29% lower risk of breast cancer-specific death compared to never using multivitamins. Continual use of multivitamins with minerals from the pre- to post-diagnosis period at least three times/week compared to never use was found to be associated with a 31% lower risk of recurrence. However, this result might be valid only for women who underwent radiotherapy as part of their breast cancer treatment since when the results were analyzed by treatment type, women who underwent radiation treatment benefitted the most. No associations were found for taking multivitamins without minerals and breast cancer recurrence, breast cancer-specific death or overall mortality.

Comments regarding the study

This study is the first to examine multivitamin use and breast cancer outcomes, but there have been a number of studies examining the associations between vitamin use and risk of breast cancer. Some of these studies have reported disturbing results, indicating that vitamins could increase breast cancer risk for some women, especially those who are not actually deficient. The above study controls for many breast cancer-related risk factors, but suffers from recall bias and a relatively small sample size of multivitamin without mineral use (which makes it impossible to interpret the finding that only multivitamin formulations that also include minerals such as calcium, magnesium and zinc improve outcomes). Also, women who take multivitamins may be more likely to eat a healthy diet, which could also influence prognosis.