Should women undergoing treatment for breast cancer take antioxidant supplements?

An important study just published in Cancer Epidemiology, Biomarkers & Prevention adds to the  evidence that supplementation can be helpful rather than an impediment to oxidizing therapies. The authors set out to address a concern that has persisted in the face of mounting evidence to the contrary:

"Antioxidants may protect normal cells from the oxidative damage that occurs during radiotherapy and certain chemotherapy regimens; however, the same mechanism could protect tumor cells and potentially reduce effectiveness of cancer treatments. We evaluated the association of vitamin supplement use in the first 6 months after breast cancer diagnosis and during cancer treatment with total mortality and recurrence."

They evaluated 4,877 women diagnosed with invasive breast cancer in Shanghai, China, between March 2002 and April 2006 for the correlation between supplement use and breast cancer total mortality and recurrence. Women were interviewed approximately 6 months after diagnosis and followed up by interviews and records. What did the data show?

"Vitamin use shortly after breast cancer diagnosis was associated with reduced mortality and recurrence risk, adjusted for multiple lifestyle factors, sociodemographics, and known clinical prognostic factors. Women who used antioxidants (vitamin E, vitamin C, multivitamins) had 18% reduced mortality risk and 22% reduced recurrence risk. "

Interestingly, in this study...

"The inverse association was found regardless of whether vitamin use was concurrent or nonconcurrent with chemotherapy, but was present only among patients who did not receive radiotherapy."

The data were sufficient for the authors to conclude:

"Vitamin supplement use in the first 6 months after breast cancer diagnosis may be associated with reduced risk of mortality and recurrence...Our results do not support the current recommendation that breast cancer patients should avoid use of vitamin supplements."