Mega-dose vitamins and minerals in the treatment of non-metastatic breast cancer: an historical cohort study.

BACKGROUND: Alternative therapies such as mega-dose vitamins and minerals are commonly used by women with breast cancer, but their effect on recurrence and survival have rarely been evaluated.
METHODS: Survival and recurrence outcomes for 90 women with unilateral non-metastatic breast cancer diagnosed between 1989 and 1998, and who had been prescribed mega-doses of beta-carotene, vitamin C, niacin, selenium, coenzyme Q10, and zinc in addition to standard therapies were compared with matched controls. The 90 treated patients were prescribed combinations from three to six of the vitamins and minerals listed above. The controls were matched (2:1) to the vitamin/mineral patients for age at diagnosis, presence of axillary lymph node metastasis, tumor stage, grade, estrogen receptor status, year of diagnosis, and prescription of systemic therapy. All subjects were patients of the British Columbia Cancer Agency, Vancouver Island Centre.
FINDINGS: Median follow-up of surviving patients was 68 months (minimum 20 months, 133 months maximum). The vitamin/mineral patients and controls were well matched. Two endpoints were considered. Breast cancer-specific survival (p = 0.19) and disease-free survival (p = 0.08) times for the vitamin/mineral treated group were shorter, after adjusting for diagnostic variables using a Cox proportional hazards model. The hazard ratios for the vitamin/mineral treated group versus the control group were estimated at 1.75 (95% CI = 0.83-2.69) for disease-specific survival and 1.55 (95% CI = 0.94-2.54) for disease-free survival. Overall survival was similar for the two groups (log-rank test, p = 0.36).
INTERPRETATION: Breast cancer-specific survival and disease-free survival times were not improved for the vitamin/mineral treated group over those for the controls.