Vitamins do not worsen breast cancer outcome
MedWire News: Vitamin use shortly after breast cancer diagnosis does not have a detrimental effect on patient outcome, according to research published in the journal Cancer Epidemiology, Biomarkers and Prevention.
"Instead, vitamin use, particularly vitamin C and vitamin E use, may be associated with reduced risk of mortality and recurrence," report Xiao Ou Shu (Vanderbilt University School of Medicine, Nashville, Tennessee, USA) and colleagues.
"There is a widespread concern that the use of anti-oxidant supplements during cancer treatment may protect tumor cells from the oxidative damage induced by cancer therapies, thereby reducing the effectiveness of treatment and increasing risk of mortality," note the researchers.
Yet, the epidemiologic data to support this concern are limited, particularly among breast cancer patients. Shu and team therefore evaluated the association of vitamin supplement use in the first 6 months after breast cancer diagnosis and during cancer treatment with total mortality and disease recurrence.
They followed up 4877 women, aged 20 to 75 years, diagnosed with invasive breast cancer in Shanghai, China, for a mean period of 4.1 years. During this time 444 women died and 532 experienced breast cancer recurrence.
Patient interviews - conducted approximately 6 months after diagnosis - indicated that approximately one third (36.4%) of breast cancer survivors used any type of vitamin supplement after diagnosis.
Vitamin C was the most commonly used supplement (17.5%), followed by B vitamins (16.3%), vitamin E (7.6%), vitamin A (1.7%), and vitamin D (0.4%). In addition, about 11% used multivitamins.
The researchers found that use of any vitamins within the first 6 months of breast cancer diagnosis was associated with reduced mortality and recurrence risk, even after adjustment for multiple lifestyle, sociodemographic, and known clinical prognostic factors.
More specifically, women who used antioxidants (vitamin E, vitamin C, or multivitamins) had an 18% reduced mortality risk and a 22% reduced recurrence risk compared with women who reported no postdiagnosis vitamin use.
The reduced risk occurred regardless of whether vitamin use was concurrent or nonconcurrent with chemotherapy, but was present only among patients who did not receive radiotherapy.
Shu and co-authors conclude that their results "do not support the current recommendation that breast cancer patients should avoid use of vitamin supplements."
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By Laura Dean