Melatonin and Vitamin D in Breast Cancer

Official Title

Anti-proliferative Effects of Melatonin and Vitamin D in Breast Cancer


The investigators want to study whether Vitamin D and melatonin can reduce the growth of cancer cells in women with breast cancer. Studies using cell cultures and animals have shown that Vitamin D can reduce the spread of cancer. Studies in people have shown that exposure to sun and eating foods containing high levels of Vitamin D can protect against cancer. As well, researchers have noticed that an increase in melatonin levels appears to lower the risk of getting cancer. Melatonin is a hormone secreted by the body during the night while sleeping. Women with cancer proven by breast biopsy who are planned for surgery will be included. The investigators want to see if treatment with Vitamin D (2000 IU daily), or melatonin (20 mg daily), or both pills together, reduces the growth of cancer cells when compared to treatment with sugar pills. All women will receive identical appearing pills for approximately four weeks. The investigators will measure a tumour protein called Ki67 in the biopsy and in the tumour removed at surgery. Ki67 provides information on how rapidly the cancer grows. The reduction in Ki67 levels between the biopsy and surgery will be compared between the four groups. Vitamin D and melatonin are inexpensive with few side effects. If a reduction in cancer growth rate is shown then this would provide a strong reason for further large cancer prevention trials with Vitamin D and melatonin.

Trial Description

Primary Outcome:

  • Proliferation rate
Secondary Outcome:
  • MicroRNA
This study aims to investigate the effects of Vitamin D and melatonin on breast cancer proliferation in a randomized trial. Both agents have been associated with anti-cancer action in both epidemiological and experimental studies. However, there has been some discrepancy observed in evidence supporting their preventive function in population and clinical studies, likely related to a lack of knowledge on the exact preventive activity. Our proposed study is the first to use an innovative pre-operative chemoprevention approach. The investigators hypothesize that supplementation with Vitamin D and separately melatonin decreases the proliferative activity in breast cancer lesions. The investigators will evaluate whether treatment with Vitamin D (2000 IU/day) or melatonin (20 mg/day) reduces tumour proliferation compared to placebo, as measured by Ki67. A factorial design will be used where 144 women who have biopsy-proven breast cancer will be randomized to: a) Vitamin D, b) melatonin, c) both or d) placebo prior to their surgery. Treatment will be for approximately four weeks. The Ki67 marker will be measured on the tumour tissue. Change in Ki67 scores between the biopsy and surgery will be compared between the four groups. Blood samples will also be collected and studied at a later time on the mechanisms of action of Vitamin D and melatonin. The proposed study is innovative in its approach and content and has the potential to deeply improve strategies for cancer prevention.

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Canadian Cancer Society

These resources are provided in partnership with the Canadian Cancer Society